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Linux in a Nutshell, third Edition

Pages 1--1041 from Linux in a Nutshell, 3rd Edition

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Linux in a Nutshell, 3rd Edition
By Ellen Siever, Stephen Spainhour, Stephen Figgins and Jessica P. Hekman
ISBN 0-596-00025-1
Third Edition, published August 2000
(See the catalog page for this book.)

Table of Contents
Copyright Page
Preface
Chapter 1: Introduction
Chapter 2: System and Network Administration Overview
Chapter 3: Linux Commands
Chapter 4: Boot Methods
Chapter 5: Red Hat and Debian Package Managers
Chapter 6: The Linux Shells: An Overview
Chapter 7: bash: The Bourne-Again Shell
Chapter 8: csh and tcsh
Chapter 9: Pattern Matching
Chapter 10: The Emacs Editor
Chapter 11: The vi Editor
Chapter 12: The sed Editor
Chapter 13: The gawk Scripting Language
Chapter 14: CVS and RCS
Chapter 15: GNOME
Chapter 16: KDE
Chapter 17: An Alternative Window Manager: fvwm2
Index
Colophon

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(Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

Copyright © 2000, 1999, 1997 O'Reilly & Associates, Inc. All rights reserved.
Printed in the United States of America.
Published by O'Reilly & Associates, Inc., 101 Morris Street, Sebastopol, CA 95472.
The O'Reilly logo is a registered trademark of O'Reilly & Associates, Inc. Many of the
designations used by manufacturers and sellers to distinguish their products are claimed as
trademarks. Where those designations appear in this book, and O'Reilly & Associates, Inc.
was aware of a trademark claim, the designations have been printed in caps or initial caps.
The use of the horse image in association with Linux is a trademark of O'Reilly & Associates,
Inc.

While every precaution has been taken in the preparation of this book, the publisher assumes
no responsibility for errors or omissions, or for damages resulting from the use of the
information contained herein.

Table of Contents 0. Preface
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Preface (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

Preface
This is a book about Linux, a freely available clone of the Unix operating system for personal
computers. Linux was first developed by Linus Torvalds, who built the first Linux kernel and
continues to centrally coordinate improvements. The operating system continues to grow
under the dedicated cultivation of a host of other programmers and hackers all over the world,
all connected through the Internet. Beyond the kernel code, Linux includes utilities and
commands from the Free Software Foundation's GNU project, Berkeley Unix (BSD), and a
complete port of the X Window System (XFree86) from the X Consortium, in addition to
many features written specifically for Linux. Even more recent projects extend Linux in
exciting ways, some through changes to the kernel --such as real-time scheduling and RAID
support --and some through libraries and applications that radically change the user's
experience; the GNOME and KDE desktops briefly covered in this book are the most
prominent examples.

This book is a quick reference for the basic commands and features of the Linux operating
system. As with other books in O'Reilly's "In a Nutshell" series, this book is geared toward
users who know what they want to do and have some idea how to do it, but just can't
remember the correct command or option. We hope this guide will become an invaluable
desktop reference for the Linux user.

0.1. Other Resources
This book will not tell you how to install and maintain a Linux system. For that, you will
probably want O'Reilly's Learning Red Hat Linux or Learning Debian GNU/ Linux, by Bill
McCarty, which contain Linux distributions on CD-ROM and provide help with installation
and configuration. Alternatively, Running Linux by Matt Welsh, Matthias Kalle Dalheimer,
and Lar Kaufman is an in-depth guide suitable for all major distributions. For networking
information, check out Linux Network Administrator's Guide by Olaf Kirch and Terry
Dawson. In addition to O'Reilly's Linux titles, our wide range of Unix, X, Perl, and Java titles
may also be of interest to the Linux user.

0.1.1. Online Documentation

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Preface (Linux in a Nutshell, 3rd Edition)
The Internet is also full of information about Linux. One of the best resources is the Linux
Documentation Project at http:// www. linuxdoc. org. It has numerous short guides called

HOWTOs, along with some full manuals. For online information about the GNU utilities
covered in this book, consult http:// www. gnu. org( or one of the dozens of mirror sites around

the world). The Free Software Foundation, which is in charge of GNU, publishes its
documentation in a number of hard-copy books about various tools.

0.1.2. Linux Journal and Linux Magazine
Linux Journal and Linux Magazine are monthly magazines for the Linux community, written
and published by a number of Linux activists. They contain articles ranging from novice
questions and answers to kernel programming internals. Linux Journal is the oldest magazine
and is published by S. S. C. Incorporated, http:// www. ssc. com. Linux Magazine is at

http:// www. linuxmagazine. com.

0.1.3. LinuxUsenet Newsgroups
If you have access to Usenet news, the following Linux-related newsgroups are available:
comp. os. linux. announce
A moderated newsgroup containing announcements of new software, distributions, bug
reports, and goings-on in the Linux community. All Linux users should read this
group. Submissions may be mailed to linux-announce@ news. ornl. gov.

comp. os. linux. help
General questions and answers about installing or using Linux.
comp. os. linux. admin
Discussions relating to systems administration under Linux.
comp. os. linux. networking
Discussions relating to networking with Linux.
comp. os. linux. development
Discussions about developing the Linux kernel and system itself.
comp. os. linux. misc

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A catch-all newsgroup for miscellaneous discussions that don't fall under the previous
categories.

There are also several newsgroups devoted to Linux in languages other than English, such as
fr. comp. os. linux in French and de. comp. os. linux in German.

0.1.4. Online Linux Support
There are many ways of obtaining help online, where volunteers from around the world offer
expertise and services to assist users with questions and problems.

The OpenProjects IRC Network is an IRC network devoted entirely to Open Projects --Open
Source and Open Hardware alike. Some of its channels are designed to provide online Linux
support services. IRC stands for Internet Relay Chat, and is a network service that allows you
to talk interactively on the Internet to other users. IRC networks support multiple channels on
which groups of people talk. Whatever you type in a channel is seen by all other users of that
channel.

There are a number of active channels on the OpenProjects IRC network where you will find
users 24 hours a day, 7 days a week who are willing and able to help you solve any Linux
problems you may have, or just chat. You can use this service by installing an IRC client like
irc-II, connecting to servername >irc. openprojects. org: 6667>, and joining the #linpeoplechannel.

0.1.5. Linux User Groups
Many Linux User Groups around the world offer direct support to users. Many Linux User
Groups engage in activities such as installation days, talks and seminars, demonstration
nights, and other completely social events. Linux User Groups are a great way of meeting
other Linux users in your area. There are a number of published lists of Linux User Groups.
Some of the better-known ones are:

Groups of Linux Users Everywhere
http:// www. ssc. com/ glue/ groups
LUGlist project

http:// www. nllgg. nl/ lugww
LUGregistry

http:// www. linux. org/ users

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Copyright Page 0.2. Conventions

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Conventions (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

0.2. Conventions
This desktop quick reference follows certain typographic conventions:
Bold
is used for commands, programs, and options. All terms shown in bold are typed
literally.
Italic

is used to show arguments and variables that should be replaced with user-supplied
values. Italic is also used to indicate filenames and directories and to highlight
comments in examples.
Constant Width

is used to show the contents of files or the output from commands.
Constant Width Bold

is used in examples and tables to show commands or other text that should be typed
literally by the user.
Constant Width Italic

is used in examples and tables to show text that should be replaced with user-supplied
values.
%, $

are used in some examples as the tcsh shell prompt (%) and as the Bourne or bash
shell prompt ($).
[ ]

surround optional elements in a description of syntax. (The brackets themselves should
never be typed.) Note that many commands show the argument [files]. If a filename is
omitted, standard input (e. g., the keyboard) is assumed. End with an end-of-file
character.
EOF

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Conventions (Linux in a Nutshell, 3rd Edition)
indicates the end-of-file character (normally Ctrl-D).
|

is used in syntax descriptions to separate items for which only one alternative may be
chosen at a time.

is used at the bottom of a right-hand page to show that the current entry continues on
the next page. The continuation is marked by a .

The owl icon designates a note, which is an important aside to its nearby text. For example...
NOTE
When you see the owl icon, you know the text beside it is a note, like this.
A final word about syntax. In many cases, the space between an option and its argument can
be omitted. In other cases, the spacing (or lack of spacing) must be followed strictly. For
example, -wn (no intervening space) might be interpreted differently from -w n. It's important
to notice the spacing used in option syntax.

0. Preface 0.3. We'd Like to Hear from
You

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0.3. We'd Like to Hear from You
We have tested and verified all of the information in this book to the best of our ability, but
you may find that features have changed (or even that we have made mistakes!). Please let us
know about any errors you find, as well as your suggestions for future editions, by writing:

O'Reilly & Associates, Inc. 101 Morris Street Sebastopol, CA 95472 800-998-9938 (in the
U. S. or Canada) 707-829-0515 (international/ local) 707-829-0104 (fax)

You can also send us messages electronically. To be put on the mailing list or to request a
catalog, send email to:

info@ oreilly. com
To ask technical questions or comment on the book, send email to:
bookquestions@ oreilly. com
Wehave a web site for the book, where we list examples, errata, and any plans for future
editions. You can access this page at:

http:// www. oreilly. com/ catalog/ linuxnut3

For more information about this book and others, see the O'Reilly web site:
http:// www. oreilly. com

0.2. Conventions 0.4. Acknowledgments
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.
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Acknowledgments (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

0.4. Acknowledgments
This edition of Linux in a Nutshell is the result of the cooperative efforts of many people.
Thanks to Andy Oram for his editorial skills, to Val Quercia for her project management
skills, and to both of them for pitching in to check existing chapters and update and write new
material as needed.

For technical review, thanks go to Matt Welsh of Running Linux and Installation and Getting
Started Guide fame; Michael K. Johnson of Red Hat Software; Robert J. Chassell, Phil
Hughes, and Laurie Lynne Tucker of Linux Journal; Arnold Robbins, Julian T. J. Midgley,
Terry Dawson, Doug Moreen, Ron Passerini, and Mark Stone.

0.3. We'd Like to Hear from
You
1. Introduction

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Introduction (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
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Chapter 1. Introduction
Contents:
The Excitement of Linux
Distribution and Support
Commands on Linux
What This Book Offers
Sources and Licenses
Beginner's Guide

In just a few years, Linux has grown from a student/ hacker playground to an upstart
challenger in the server market to a well-respected system taking its rightful place in
educational and corporate networks. A freely redistributable clone of the Unix operating
system, Linux is turning up everywhere. People use it for web servers, file servers, and
workstations instead of--or alongside --systems from traditional Unix vendors as well as
Windows NT. In addition to its role in large networks (because it's a friendly fellow that fits in
very nicely with other operating systems), Linux is popular among Windows users who just
want to try something that gives them more speed, more power, and more control.

The historical impact of Linux goes even beyond its own penetration into the markets of
proprietary operating systems. Its success has inspired countless other free software or open
source (http:// opensource. org) projects, including Samba, GNOME, and a mind-boggling

collection of innovative projects that you can browse at numerous sites like SourceForge
(http:// sourceforge. net). As both a platform for other developers and a development model,

Linux gave a tremendous boost to the Free Software Foundation's GNU project, which in turn
had furnished key software that made the development of Linux possible. In short, Linux is a
central participant in the most exciting and productive free software movement ever seen.

If you haven't obtained Linux yet or have it but don't know exactly how to get started using it,
see the Preface.

1.1. The Excitement of Linux
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Linux is first of all free software: anyone can download the source from the Internet or buy it
on a low-cost CD-ROM. But Linux is becoming well known because it's more than free
software --it's unusually good software. You can get more from your hardware with Linux
(particularly on Intel systems, where it was originally developed) and be assured of fewer
crashes; even its security is better than many commercial alternatives.

As free software, Linux revives the grand creativity and the community of sharing that Unix
was long known for. The unprecedented flexibility and openness of Unix--which newcomers
usually found confusing and frustrating but which they eventually found they couldn't live
without --continually inspired extensions, new tools like Perl, and experiments in computer
science that sometimes ended up in mainstream commercial computer systems.

Many fondly remember the days when AT& T provided universities with Unix source code at
no charge, and the University of Berkeley started distributing its version in any manner that
allowed people to get it. For these older hackers, Linux can bring back the spirit of working
together --all the more so because the Internet is now widespread. And for the many who are
too young to remember the first round of open systems (such as the hordes of students
attracted to Linux) or whose prior experience has been woefully constricted by proprietary
operating systems, now is the time to discover the wonders of freely distributable source code
and infinitely adaptable interfaces.

The Linux kernel itself was originally designed by Linus Torvalds at the University of
Helsinki in Finland and later developed through collaboration with countless volunteers
worldwide. By "kernel," we mean the core of the operating system itself --not the
applications (such as the compiler, shells, and so forth) that run on it. Today, the term "Linux"
is often used to mean the kernel as well as the applications and complete system environment.

Most Linux systems cannot be technically referred to as a "version of Unix," as they have not
been submitted to the required tests and licensed properly.[ 1] However, at least one Linux

distribution has in fact been branded as POSIX. 1. Linux offers all the common programming
interfaces as standard Unix systems, and as you can see from this book, all the common Unix
utilities have been reimplemented on Linux. It is a powerful, robust, fully usable system for
those who like Unix.

[1] Before an operating system can be called "Unix," it must be branded by
X/ Open.

The economic power behind Linux's popularity is its support for an enormous range of
hardware used with IBM-compatible personal computers. People who are accustomed to MS-DOS
and Microsoft Windows are often amazed at how much faster their hardware appears to
work with Linux --it makes efficient use of its resources.

For the first several years, users were attracted to Linux for a variety of financial and political
reasons, but soon they discovered an unexpected benefit: it works better than many

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Introduction (Linux in a Nutshell, 3rd Edition)
commercial systems. With the Samba file and print server, for instance, Linux serves a large
number of end-user PCs without crashing. With the Apache web server, it provides more of
the useful features web administrators want than competing products do.

0.4. Acknowledgments 1.2. Distribution and Support
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Distribution and Support (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

1.2. Distribution and Support
While it is convenient to download one or two new programs over the Internet and fairly
feasible to download something as large as the Linux kernel, getting a whole working system
over phone lines is an absurd proposition. Over the years, therefore, commercial and
noncommercial packages called distributions have emerged. The first consisted of
approximately 50 diskettes, at least one of which would usually turn out to be bad and have to
be replaced. When CD-ROM drives became widespread, Linux really took off.

After getting Linux, the average user is concerned next with support. While Usenet
newsgroups offer very quick response and meet the needs of many intrepid users, you can also
buy support from the vendors of the major distributions and a number of independent experts.
Linux is definitely supported at least as well as commercial software.

Intel is still by far the most common hardware running Linux, but Linux is also now
commercially available on a number of other hardware systems, notably the PowerPC, the 64-
bit Intel Itanium processor, the Alpha (created by Digital Equipment Corporation, now
Compaq), the SPARC, and the MIPS chip.

1. Introduction 1.3. Commands on Linux
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Commands on Linux (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
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1.3. Commands on Linux
Linux commands are not the same as standard Unix ones. They're better! This is because most
of them are provided by the GNU project run by the Free Software Foundation (FSF). GNU
means "GNU's Not Unix" --the first word of the phrase is supposed to be expanded with
infinite recursion.

Benefiting from years of experience with standard Unix utilities and advances in computer
science, programmers on the GNU project have managed to create versions of standard tools
that have more features, run faster and more efficiently, and lack the bugs or inconsistencies
that persist in the original standard versions.

While GNU provided the programming utilities and standard commands like grep, most of the
system and network administration tools on Linux came from the Berkeley Software
Distribution (BSD). In addition, some people wrote tools specifically for Linux to deal with
special issues such as filesystems that only Linux supports. This book documents all the
standard Unix commands that are commonly available on most Linux distributions.

The third type of software most commonly run on Linux is the X Window System, ported by
the XFree86 project to standard Intel chips. While this book cannot cover the wide range of
utilities that run on X, we briefly cover some of the useful customizations you may want to
make to your KDE, GNOME, or fvwm desktop.

1.2. Distribution and Support 1.4. What This Book Offers
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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What This Book Offers (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

1.4. What This Book Offers
Based originally on the classic O'Reilly & Associates quick reference, Unix in a Nutshell, this
book has been expanded to include much information that is specific to Linux. The current
edition includes chapters on package managers (which make it easy to install, update, and
remove related software files), on the KDE and GNOME desktops, and on the fvwm window
manager, as well as new commands and expanded discussions of several topics such as CVS
and bash.

Linux in a Nutshell doesn't teach you Linux--it is, after all, a quick reference --but novices as
well as highly experienced users will find it of great value. When you have some idea what
command you want but aren't sure just how it works or what combinations of options give you
the exact output required, this book is the place to turn. It is also an eye-opener: it can make
you aware of options that you never knew about before.

Like computer systems from the age in which Unix was born (the early 1970s), Linux is
mostly a command-driven system. Most versions of Linux provide a few graphical tools, and
several commercial products are available, but none of these graphical utilities are central to
Linux. That is why this book, like the traditional Unix in a Nutshell reference, focuses on the
shell and on commands you run from the shell.

Of course, Linux offers a windowing system --a very rich and flexible one, as befits a rich
and flexible operating system. But a lot of the time you'll just open a simulated VT100
terminal (the xterm program) and enter commands into that. You'll find yourself moving back
and forth between graphical programs and the commands listed in this book.

So the first thing you've got to do, once you're over the hurdle of installing Linux, is get to
know the common utilities run from the shell prompt. If you know absolutely nothing about
Unix, we recommend you read a basic guide (introductory chapters in the O'Reilly books
Learning Red Hat Linux, Learning Debian GNU/ Linux, and Running Linux can get you
started). This book offers a context for understanding different kinds of commands (including
commands for programming, system administration, and network administration) in Chapter

2, "System and Network Administration Overview", followed by the command reference
itself in Chapter 3, "Linux Commands". Chapter 3, "Linux Commands" is obviously the
central focus of the book, containing about one third its bulk.

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What This Book Offers (Linux in a Nutshell, 3rd Edition)
The small chapters immediately following Chapter 3, "Linux Commands" help you get your
system set up. Since most users do not want to completely abandon other operating systems
(whether a Microsoft Windows system, OS/ 2, or some Unix flavor), Linux often resides on
the same computer as other systems. The user can boot the system he needs for a particular
job. Chapter 4, "Boot Methods", lists the commonly used booting options on Intel systems,

including LILO (Linux Loader) and Loadlin. Chapter 5, "Red Hat and Debian Package
Managers", covers the Red Hat package manager (rpm), which is supported by both the Red
Hat and the SuSE distributions, and the Debian package manager (dpkg). Package managers
are crucial for installing and updating software; they make sure you have all the files you need
in the proper versions.

All commands are interpreted by the shell. The shell is simply a program that accepts
commands from the user and executes them. Different shells sometimes use slightly different
syntax to mean the same thing. Under Linux, two popular shells are bash and tcsh, and they
differ in subtle ways. (One of the nice things about Linux, and other Unix systems is that you
have a variety of shells to choose from, each with strengths and weaknesses.) We offer several
chapters on shells. You may decide to read these after you've used Linux for a while, because
they mostly cover powerful, advanced features that you'll want when you're a steady user.

In order to get real work done, you'll have to learn some big, comprehensive utilities: notably
an editor and some scripting tools. Two major editors are used on Linux: vi and Emacs. Both
have chapters in this book. Following the editors come two chapters on classic Unix tools for
manipulating text files on a line-by-line basis: sed and gawk (the GNU version of the
traditional awk). O'Reilly also has a separate book about each of these topics that you may
find valuable, because none is completely intuitive upon first use. (Emacs does have an
excellent built-in tutorial, though; to invoke it, press Ctrl-H followed by t for "tutorial.")

CVS (Concurrent Versions System) and RCS (Revision Control System) manage files so you
can retrieve old versions and maintain different versions simultaneously. Originally used by
programmers who have complicated requirements for building and maintaining applications,
these tools have turned out to be valuable for anyone who maintains files of any type,
particularly when coordinating a team of people. CVS is a layer on top of RCS that makes it
easier for multiple people to edit a file simultaneously. Chapter 14, "CVS and RCS", presents

CVS and RCS commands.

Every distribution of Linux is slightly different, but you'll find that the commands we
document are what you use most of the time and that they work the same on all distributions.
Basic commands, programming utilities, system administration, and network administration
are all covered here. But some areas were so big that we had to leave them out. The many
applications that depend on the X Window System didn't make the cut. Nor did TeX (a text-processing
tool used extensively in academia and by Linux users in general), or the many
useful programming languages like Perl, Tcl/ Tk, and Python with which users vastly expand
the capabilities of their systems. These subjects would stretch the book out of its binding.

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What This Book Offers (Linux in a Nutshell, 3rd Edition)
Our goal in producing this book is to provide convenience, and that means keeping it small. It
certainly doesn't have everything the manual pages have. But you'll find that it has what you
need 95% of the time.

1.3. Commands on Linux 1.5. Sources and Licenses
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Sources and Licenses (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

1.5. Sources and Licenses
When you get Linux, you also get the source code. The same goes for all the utilities on Linux
(unless your vendor offered a commercial application or library as a special enhancement).
You may never bother looking at the source code, but it's key to Linux's strength. The source
code has to be provided by the vendor, under the Linux license, and it permits those who are
competent at such things to fix bugs, provide advice about the system's functioning, and
submit improvements that benefit all of us. The license is the well-known General Public
License, also known as the GPL or copyleft, invented and popularized by the Free Software
Foundation.

The FSF, founded by Richard Stallman, is a phenomenon that many people would believe to
be impossible if it did not exist. (The same goes for Linux, in fact --10 years ago, who would
have imagined a robust operating system developed by collaborators over the Internet and
made freely redistributable?) One of the most popular editors on Unix, GNU Emacs, comes
from the FSF. So do gcc and g++ (C and C++ compilers), which for a while used to set the
standard for optimization and fast code. One of the largest projects within GNU is the
GNOME desktop, which already encompasses several useful general-purpose libraries,
window managers, and applications. The GNOME developers have big plans for providing an
environment that integrates not only the applications on each user's system but also the
services provided throughout a whole organization.

Dedicated to the sharing of software, the FSF provides all its code and documentation on the
Internet and allows anyone with a whim for enhancements to alter the source code. One of its
projects is the Debian distribution of Linux.

In order to prevent hoarding, the FSF requires that the source code for all enhancements be
distributed under the same GPL that it uses. This encourages individuals or companies to
make improvements and share them with others. The only thing someone cannot do is add
enhancements and then try to sell the product as commercial software --that is, to withhold
the source code. That would be taking advantage of the FSF and the users. You can find the
GPL in any software covered by that license and online at
http:// www. gnu. org/ copyleft/ gpl. html.

As we said earlier, many tools on Linux come from BSD instead of GNU. BSD is also free

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software. The license is significantly different, but that doesn't have to concern you as a user.
The effect of the difference is that companies are permitted to incorporate the software into
their proprietary products, a practice that is severely limited by the GNU license.

1.4. What This Book Offers 1.6. Beginner's Guide
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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1.6. Beginner's Guide
If you're just beginning to work on a Linux system, the abundance of commands might prove
daunting. To help orient you, the following lists present a sampling of commands on various
topics.

1.6.1. Communication

ftp File Transfer Protocol.
login Sign on.
rlogin Sign on to remote system.
rsh Run shell or single command on remote system.
talk Exchange messages interactively with other terminals.
telnet Connect to another system.
tftp Trivial file transfer protocol.
uudecode Decode file prepared for mailing by uuencode.
uuencode Encode file containing binary characters for mailing.
vacation Respond to mail automatically.

1.6.2. Comparisons
cmp Compare two files, byte by byte.
comm Compare items in two sorted files.
diff Compare two files, line by line.
diff3 Compare three files.

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1.6.3. File Management
cat Concatenate files or display them.
chfn Change user information for finger, email, etc.
cksum Compute checksum.
chmod Change access modes on files.
chsh Change login shell.
cp Copy files.
csplit Break files at specific locations.
dd Copy files in raw disk form.
file Determine a file's type.
head Show the first few lines of a file.
less Display files by screenful.
ln Create filename aliases.
ls List files or directories.
merge Merge changes from different files.
mkdir Create a directory.
more Display files by screenful.
mv Move or rename files or directories.
newgrp Change current group.
pwd Print working directory.
rcp Copy files to remote system.
rm Remove files.
rmdir Remove directories.
split Split files evenly.
tail Show the last few lines of a file.

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wc Count lines, words, and characters.

1.6.4. Printing
lpq Show status of print jobs.
lpr Send to the printer.
lprm Remove print job.
lpstat Get printer status.
pr Format and paginate for printing.

1.6.5. Programming
ar Create and update library files.
as Generate object file.
bison Generate parsing tables.
cpp Preprocess C code.
flex Lexical analyzer.
g++ GNU C++ compiler.
gcc GNU C compiler.
ld Link editor.
m4 Macro processor.
make Create programs.
ranlib Regenerate archive symbol table.
rpcgen Translate RPC to C code.
yacc Generate parsing tables.

1.6.6. Program Maintenance
cvs Manage different versions (revisions) of source files.

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etags Generate symbol list for use with the Emacs editor.
gctags Generate symbol list for use with the vi editor.
gdb GNU debugger.
gprof Display object file's profile data.
imake Generate makefiles for use with make.
make Maintain, update, and regenerate related programs and files.
nm Display object file's symbol table.
patch Apply patches to source code.
rcs Manage different versions (revisions) of source files.
size Print the size of an object file in bytes.
strace Trace system calls and signals.
strip Strip symbols from an object file.

1.6.7. Searching
apropos Search manpages for topic.
egrep Extended version of grep.
fgrep Search files for literal words.
find Search the system for filenames.
grep Search files for text patterns.
strings Search binary files for text patterns.
whereis Find command.

1.6.8. Shell Programming
echo Repeat command-line arguments on the output.
expr Perform arithmetic and comparisons.
printf Format and print command-line arguments.

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sleep Pause during processing.
test Test a condition.

1.6.9. Storage
bzip2 Compress files to free up space.
cpio Create and unpack file archives.
gunzip Expand compressed (. gz and .Z) files (preferred).
gzip Compress files to free up space.
shar Create shell archive.
tar Copy files to or restore files from an archive medium.
zcat Display contents of compressed files.

1.6.10. System Status
at Execute commands later.
atq Show jobs queued by at.
atrm Remove job queued by at.
chgrp Change file group.
chown Change file owner.
crontab Automate commands.
date Display or set date.
df Show free disk space.
du Show disk usage.
env Show environment variables.
finger Display information about users.
kill Terminate a running command.
printenv Show environment variables.

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ps Show processes.
stty Set or display terminal settings.
who Show who is logged on.

1.6.11. Text Processing
col Process control characters.
cut Select columns for display.
ex Line editor underlying vi.
expand Convert tabs to spaces.
fmt Produce roughly uniform line lengths.
fold Break lines.
gawk Process lines or records one by one.
ghostscript Display PostScript or PDF file.
groff Format troff input.
ispell Interactively check spelling.
join Merge different columns into a database.
paste Merge columns or switch order.
rev Print lines in reverse.
sed Noninteractive text editor.
sort Sort or merge files.
tac Print lines in reverse.
tr Translate (redefine) characters.
uniq Find repeated or unique lines in a file.
vi Visual text editor.
xargs Process many arguments in manageable portions.

1.6.12. Miscellaneous
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banner Make posters from words.
bc Arbitrary precision calculator.
cal Display calendar.
clear Clear the screen.
man Get information on a command.
nice Reduce a job's priority.
nohup Preserve a running job after logging out.
passwd Set your login password.
script Produce a transcript of your login session.
su Become a superuser.
tee Simultaneously store output in file and send to screen.
which Print pathname of a command.

1.5. Sources and Licenses 2. System and Network
Administration Overview

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Chapter 2. System and Network
Administration Overview
Contents:
Common Commands
Overview of Networking
Overview of TCP/ IP
Overview of Firewalls and Masquerading
Overview of NFS
Overview of NIS
Administering NIS
RPC and XDR

2.1. Common Commands
Following are lists of commonly used system administration commands.

2.1.1. Clocks

hwclock Manage hardware clock.
netdate Set clock according to host's clock.
rdate Manage time server.
zdump Print list of time zones.
zic Create time conversion information files.

2.1.2. Daemons

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apmd Advanced Power Management daemon.
bootpd Internet Boot Protocol daemon.
fingerd Finger daemon.
ftpd File Transfer Protocol daemon.
gated Manage routing tables between networks.
identd Identify user running TCP/ IP process.
imapd IMAP mailbox server daemon.
inetd Internet services daemon.
kerneld Provide automatic kernel module loading.
klogd Manage syslogd.
lpd Printer daemon.
mountd NFS mount request server.
named Internet domain name server.
nfsd NFS daemon.
pop2d POP server.
pop3d POP server.
powerd Monitor UPS connection.
pppd Maintain Point-to-Point Protocol (PPP) network connections.
rdistd Remote file distribution server.
rexecd Remote execution server.
rlogind rlogin server.
routed Routing daemon.
rshd Remote shell server.
rwhod Remote who server.
syslogd System logging daemon.
talkd Talk daemon.

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tcpd TCP network daemon.
tftpd Trivial File Transfer Protocol daemon.
update Buffer flush daemon.
ypbind NIS binder process.
yppasswdd NIS password modification server.
ypserv NIS server process.

2.1.3. Hardware
agetty Start user session at terminal.
arp Manage the ARP cache.
cardctl Control PCMCIA cards.
cardmgr PCMCIA card manager daemon.
cfdisk Maintain disk partitions (graphical interface).
fdisk Maintain disk partitions.
getty Start user session at terminal.
kbdrate Manage the keyboard's repeat rate.
ramsize Print information about RAM disk.
setserial Set serial port information.
slattach Attach serial lines as network interfaces.

2.1.4. Host Information
arch Print machine architecture.
dnsdomainname Print DNS domain name.
domainname Print NIS domain name.
free Print memory usage.
host Print host and zone information.

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hostname Print or set hostname.
nslookup Query Internet domain name servers.
uname Print host information.

2.1.5. Installation
cpio Copy file archives.
install Copy files into locations providing user access and set permissions.
rdist Distribute files to remote systems.
tar Copy files to or restore files from an archive medium.

2.1.6. Mail
fetchmail Retrieve mail from remote servers.
formail Convert input to mail format.
mailq Print a summary of the mail queue.
makemap Update sendmail's database maps.
rmail Handle uucp mail.
sendmail Send and receive mail.

2.1.7. Managing Filesystems
To Unix systems, a filesystem is some device (such as a hard drive, floppy, or CD-ROM) that
is formatted to store files. Filesystems can be found on hard drives, floppies, CD-ROMs, or
other storage media that permit random access.

The exact format and means by which the files are stored are not important; the system
provides a common interface for all filesystem types that it recognizes. Under Linux,
filesystem types include the Second Extended Filesystem, or ext2fs, which you probably use
to store Linux files. The second extended filesystem was developed primarily for Linux and
supports 256-character filenames, 4-terabyte maximum filesystem size, and other useful
features. (It is "second" because it is the successor to the extended filesystem type.) Other
common filesystem types include the MS-DOS filesystem, which allows files on MS-DOS
partitions and floppies to be accessed under Linux, and the ISO 9660 filesystem used by CD-file:///

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ROMs.

debugfs Debug extfs filesystem.
dosfsck Check and repair a DOS or VFAT filesystem.
dumpe2fs Print information about superblock and blocks group.
e2fsck Check and repair a second extended filesystem.
fdformat Format floppy disk.
fsck Check and repair filesystem.
fsck. minix Check and repair a MINIX filesystem.
fuser List processes using a filesystem.
mke2fs Make new second extended filesystem.
mkfs Make new filesystem.
mkfs. ext2 Another name for mke2fs.
mkfs. minix Make new MINIX filesystem.
mklost+ found Make lost+ found directory.
mkraid Set up a RAID device.
mkswap Designate swap space.
mount Mount a filesystem.
raidstart Activate a RAID device.
raidstop Turn off a RAID device.
rdev Describe or change values for root filesystem.
rootflags List or set flags to use in mounting root filesystem.
showmount List exported directories.
swapdev Display or set swap device information.
swapoff Cease using device for swapping.
swapon Begin using device for swapping.
sync Write filesystem buffers to disk.

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tune2fs Manage second extended filesystem.
umount Unmount a filesystem.

2.1.8. Managing the Kernel
depmod Create module dependency listing.
insmod Install new kernel module.
lsmod List kernel modules.
modprobe Load new module and its dependent modules.
rmmod Remove module.

2.1.9. Networking
dip Establish dial-up IP connections.
gdc Administer gated routing daemon.
ifconfig Manage network interfaces.
ipchains Administer firewall facilities (2.2 kernel).
iptables Administer firewall facilities (2.4 kernel).
named Translate between domain names and IP addresses.
netstat Print network status.
portmap Map daemons to ports.
rarp Manage RARP table.
route Manage routing tables.
routed Dynamically keep routing tables up-to-date.
rpcinfo Report RPC information.
ruptime Check how long remote system has been up.
rwho Show who is logged in to remote system.
systat Show status of remote systems.

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traceroute Trace network route to remote host.

2.1.10. NIS Administration
domainname Set or display name of current NIS domain.
makedbm Rebuild NIS databases.
ypbind Connect to NIS server.
ypcat Print values in NIS database.
ypchfn Change user information in NIS database for finger, email, etc.
ypchsh Change user login shell in NIS database.
ypinit Build new NIS databases.
ypmatch Print value of one or more NIS keys.
yppasswd Change user password in NIS database.
yppasswdd Update NIS database in response to yppasswd.
yppoll Determine version of NIS map at NIS server.
yppush Propagate NIS map.
ypserv NIS server daemon.
ypset Point ypbind at a specific server.
ypwhich Display name of NIS server or map master.
ypxfr Transfer NIS database from server to local host.

2.1.11. Printing
lpc Control line printer.
tunelp Tune the printer parameters.

2.1.12. Security and System Integrity
badblocks Search for bad blocks.

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chroot Change root directory.

2.1.13. Starting and Stopping the System
bootpd Internet Boot Protocol daemon.
bootpgw Internet Boot Protocol gateway.
bootptest Test bootpd.
halt Stop or shut down system.
init Change runlevel.
reboot Shut down, then reboot system.
runlevel Print system runlevel.
shutdown Shut down system.
telinit Change the current runlevel.
uptime Display uptimes of local machines.

2.1.14. System Activity and Process Management
A number of additional commands in Chapter 3, "Linux Commands", are particularly useful
in controlling processes, including kill, killall, killall5, pidof, ps, and who.

fuser Identify processes using file or filesystem.
psupdate Update /boot/ psupdate.
renice Change the priority of running processes.
top Show most CPU-intensive processes.

2.1.15. Users
chpasswd Change multiple passwords.
groupadd Add a new group.
groupdel Delete a group

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groupmod Modify groups.
grpck Check the integrity of group system files.
grpconv Convert group file to shadow group file.
lastlog Generate report of last user login times.
newusers Add new users in a batch.
pwck Check the integrity of password system files.
pwconv Convert password file to shadow passwords.
rusers Print who-style information on remote machines.
rwall Print a message to remote users.
useradd Add a new user.
userdel Delete a user and her home directory.
usermod Modify a user's information.
w List logged-in users.
wall Write to all users.
whoami Show how you are currently logged in.

2.1.16. Miscellaneous
cron Schedule commands for specific times.
dmesg Print bootup messages after the system is up.
ldconfig Update library links and do caching.
logger Send messages to the system logger.
logrotate Compress and rotate system logs.
rstat Display host's system status.
run-parts Run all scripts in a directory.

1.6. Beginner's Guide 2.2. Overview of Networking
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Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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2.2. Overview of Networking
Networks connect computers so that the different systems can share information. For users
and system administrators, Unix systems have traditionally provided a set of simple but
valuable network services, which let you check whether systems are running, refer to files
residing on remote systems, communicate via electronic mail, and so on.

For most commands to work over a network, each system must be continuously running a
server process in the background, silently waiting to handle the user's request. This kind of
process is called a daemon; common examples, on which you rely for the most basic functions
of your Linux system, are named (which translates numeric IP addresses into the
alphanumeric names that humans are so fond of), lpd (which sends documents to a printer,
possibly over a network), and ftpd (which allows you to connect to another machine via ftp).

Most Unix networking commands are based on Internet protocols. These are standardized
ways of communicating across a network on hierarchical layers. The protocols range from
addressing and packet routing at a relatively low layer to finding users and executing user
commands at a higher layer.

The basic user commands that most systems support over Internet protocols are generally
called TCP/ IP commands, named after the two most common protocols. You can use all of
these commands to communicate with other Unix systems besides Linux systems. Many can
also be used to communicate with non-Unix systems, because a wide variety of systems
support TCP/ IP.

This section also covers NFS and NIS, which allow for transparent file and information
sharing across networks, and sendmail.

2.2.1. TCP/ IP Administration

ftpd Server for file transfers.
gated Manage routing tables between networks.
host Print host and zone information.

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ifconfig Configure network interface parameters.
named Translate between domain names and IP addresses.
netstat Print network status.
nslookup Query domain name servers.
ping Check that a remote host is online and responding.
pppd Create PPP serial connection.
rdate Notify time server that date has changed.
route Manage routing tables.
routed Dynamically keep routing tables up to date.
slattach Attach serial lines as network interfaces.
telnetd Server for Telnet sessions from remote hosts.
tftpd Server for restricted set of file transfers.

2.2.2. NFS and NIS Administration
domainname Set or display name of current NIS domain.
makedbm Rebuild NIS databases.
portmap DARPA port to RPC program number mapper.
rpcinfo Report RPC information.
ypbind Connect to NIS server.
ypcat Print values in NIS database.
ypinit Build new NIS databases.
ypmatch Print value of one or more NIS keys.
yppasswd Change user password in NIS database.
yppasswdd Update NIS database in response to yppasswd.
yppoll Determine version of NIS map at NIS server.
yppush Propagate NIS map.

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ypserv NIS server daemon.
ypset Point ypbind at a specific server.
ypwhich Display name of NIS server or map master.
ypxfr Transfer NIS database from server to local host.

2. System and Network
Administration Overview
2.3. Overview of TCP/ IP

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2.3. Overview of TCP/ IP
TCP/ IP is a set of communications protocols that define how different types of computers talk
to one another. It's named for its two most common protocols, the Transmission Control
Protocol and the Internet Protocol. The Internet Protocol moves data between hosts: it splits
data into packets, which are then forwarded to machines via the network. The Transmission
Control Protocol ensures that the packets in a message are reassembled in the correct order at
their final destination and that any missing datagrams are resent until they are correctly
received. Other protocols provided as part of TCP/ IP include:

Address Resolution Protocol (ARP)
Translates between Internet and local hardware addresses (Ethernet et al.)
Internet Control Message Protocol (ICMP)
Error-message and control protocol
Point-to-Point Protocol (PPP)
Enables TCP/ IP (and other protocols) to be carried across both synchronous and
asynchronous point-to-point serial links

Reverse Address Resolution Protocol (RARP)
Translates between local hardware and Internet addresses (opposite of ARP)
Serial Line Internet Protocol (SLIP)
Carries IP over serial lines
Simple Mail Transport Protocol (SMTP)
Used by sendmail to send mail via TCP/ IP

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Simple Network Management Protocol (SNMP)

Performs distributed network management functions via TCP/ IP
User Datagram Protocol (UDP)
Provides data transfer, without the reliable delivery capabilities of TCP
Background about TCP/ IP is described in the three-volume set Internetworking with TCP/ IP
by Douglas R. Comer, published by Prentice-Hall. The commands in this chapter and the next
are described in more detail in TCP/ IP Network Administration, 2d ed., by Craig Hunt and
Linux Network Administrator's Guide by Olaf Kirch and Terry Dawson, both published by
O'Reilly & Associates.

In the architecture of TCP/ IP protocols, data is passed down the stack (toward the Network
Access Layer) when it is being sent to the network and up the stack when it is being received
from the network (see Figure 2-1).

Figure 2-1. Layers in the TCP/ IP protocol architecture
2.3.1. IP Addresses
The IP (Internet) address is a 32-bit binary number that differentiates your machine from all
others on the network. Each machine must have a unique IP address. An IP address contains
two parts: a network part and a host part. The number of address bits used to identify the
network and host differ according to the class of the address. There are three main address
classes: A, B, and C (see Figure 2-2). The leftmost bits indicate what class each address is.

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Figure 2-2. IP address structure
A more recent standard called Classless Inter-Domain Routing (CIDR) extends the class
system's idea of using initial bits to identify where packets should be routed. Under CIDR, a
new domain can be created with any number of fixed leftmost bits (not just a multiple of 8).

Another new standard called IPv6 changes the method of addressing and increases the number
of fields, but it will be a while before anyone uses it.

If you wish to connect to the Internet, contact the Network Information Center and have them
assign you a network address. If you are not connecting to an outside network, you can choose
your own network address, as long as it conforms to the IP address syntax. You should use
special reserved addresses provided for in RFC 1597, which lists IP network numbers for
private networks that don't have to be registered with the IANA (Internet Assigned Numbers
Authority). An IP address is different from an Ethernet address, which is assigned by the
manufacturer of the physical Ethernet card.

2.3.2. Gateways and Routing
Gateways are hosts responsible for exchanging routing information and forwarding data from
one network to another. Each portion of a network that is under a separate local administration
is called an autonomous system (AS). Autonomous systems connect to each other via exterior

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gateways. An AS also may contain its own system of networks, linked via interior gateways.

2.3.2.1. Gateway protocols
Gateway protocols include:
EGP (Exterior Gateway Protocol)
BGP (Border Gateway Protocol)

Protocols for exterior gateways to exchange information
RIP (Routing Information Protocol)
Interior gateway protocol; most popular for LANs
Hello Protocol
OSPF (Open Shortest Path First)

Interior gateway protocol

2.3.2.2. Routing daemons
gated and routed, the routing daemons, can be run on a host to make it function as a gateway.
Only one of them can run on a host at any given time. gated is the gateway routing daemon
and allows a host to function as both an exterior and interior gateway. It simplifies the routing
configuration by combining the protocols RIP, Hello, BGP, EGP, and OSPF into a single
package.

routed, a network routing daemon that uses RIP, allows a host to function as an interior
gateway only. routed manages the Internet routing tables. For more details on gated and
routed, see Chapter 3, "Linux Commands".

2.3.2.3. Routing tables
Routing tables provide information needed to route packets to their destinations. This
information includes destination network, gateway to use, route status, and number of packets
transmitted. Routing tables can be displayed with the netstat command.

2.3.3. Name Service
Each host on a network has a name that points to information about the host. Hostnames can
be assigned to any device that has an IP address. Name service translates the hostnames (easy
for people to remember) to IP addresses (the numbers the computer deals with).

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2.3.3.1. DNS and BIND
The Domain Name System (DNS) is a distributed database of information about hosts on a
network. Its structure is similar to that of the Unix filesystem --an inverted tree, with the root
at the top. The branches of the tree are called domains (or subdomains) and correspond to IP
addresses. The most popular implementation of DNS is the BIND (Berkeley Internet Name
Domain) software.

DNS works as a client/ server application. The resolver is the client, the software that asks
questions about host information. The name server is the process that answers the questions.
The server side of BIND is the named daemon. You can interactively query name servers for
host information with the nslookup command. For more details on named and nslookup, see
Chapter 3, "Linux Commands".

As the name server of its domain, your machine would be responsible for keeping (and
providing on request) the names of the machines in its domain. Other name servers on the
network would forward requests for these machines to it.

2.3.3.2. Domain names
The full domain name is the sequence of names, starting from the current domain and going
back to the root, with a period separating the names. For instance, oreilly. com indicates the
domain oreilly (for O'Reilly & Associates), which is under the domain com (for commercial).
One machine under this domain is www. oreilly. com. Top-level domains include:

com
Commercial organizations
edu
Educational organizations
gov
Government organizations
mil
Military departments
net

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Commercial Internet organizations, usually Internet service providers

org
Miscellaneous organizations
Countries also have top-level domains.

2.3.4. Configuring TCP/ IP
2.3.4.1. ifconfig
The network interface represents the way that the networking software uses the hardware --
the driver, the IP address, and so forth. To configure a network interface, use the ifconfig
command. With ifconfig, you can assign an address to a network interface, setting the
netmask, broadcast address, and IP address at boot time. You can also set network interface
parameters, including the use of ARP, the use of driver-dependent debugging code, the use of
one-packet mode, and the address of the correspondent on the other end of a point-to-point
link. For more information on ifconfig, see Chapter 3, "Linux Commands".

2.3.4.2. Serial-line communication
There are two protocols for serial-line communication: Serial Line IP (SLIP) and Point-to-Point
Protocol (PPP). These protocols let computers transfer information using the serial port
instead of a network card and a serial cable in place of an Ethernet cable.

Under Linux, the SLIP driver is installed in the kernel. To convert a serial line to SLIP mode,
use the slattach program (details on slattach are available in Chapter 3, "Linux Commands").

Don't forget that after putting the line in SLIP mode, you still have to run ifconfig to configure
the network interface. For example, if your machine is named tanuki and you have dialed in
to ruby:

# ifconfig s10 tanuki pointopoint ruby # route add ruby # route add default gw ruby

This configures the interface as a point-to-point link to ruby, adds the route to ruby, and
makes it a default route, specifying ruby as the gateway.

PPP was intended to remedy some of SLIP's failings; it can hold packets from non-Internet
protocols, it implements client authorization and error detection/ correction, and it dynamically
configures each network protocol that passes through it. Under Linux, PPP exists as a driver
in the kernel and as the daemon pppd. For more information on pppd, see Chapter 3, "Linux

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Commands".

2.3.5. Troubleshooting TCP/ IP
The following commands can be used to troubleshoot TCP/ IP. For more details on these
commands, see Chapter 3, "Linux Commands".

ifconfig
Provide information about the basic configuration of the network interface.
netstat

Display network status.
ping

Indicate whether a remote host can be reached.
nslookup

Query the DNS name service.
traceroute

Trace route taken by packets to reach network host.

2.2. Overview of Networking 2.4. Overview of Firewalls
and Masquerading

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2.4. Overview of Firewalls and Masquerading
A firewall computer is a secure system that sits between an internal network and an external
network (i. e., the Internet). It is configured with a set of rules that it uses to determine what
traffic is allowed to pass and what traffic is barred. While a firewall is generally intended to
protect the network from malicious or even accidentally harmful traffic from the outside, it
can also be configured to monitor traffic leaving the network. As the sole entry point into the
system, the firewall makes it easier to construct defenses and monitor activity.

The firewall can also be set up to present a single IP address to the outside world, even though
it may use multiple IP addresses internally. This is known as masquerading. Masquerading
can act as additional protection hiding the very existence of a network. It also saves the
trouble and expense of obtaining multiple IP addresses.

NOTE
The discussion of iptables applies to Version 2.4 Linux kernels. As this book
was being written, both iptables and the 2.4 kernel were still in development.
The final product may differ slightly from what we describe here. See the
O'Reilly book Linux Network Administrator's Guide by Olaf Kirch and Terry
Dawson or the the "Linux IPTABLES-HOWTO" for more information. This
HOWTO, and a myriad of others, can be obtained from the the Linux
Documentation Project web sites (see the Preface).

IP firewalling and masquerading are implemented in Linux Version 2.2 with the ipchains
utility and in Linux Version 2.4 with the iptables facility. The 2.0 kernels used a command
called ipfwadm, which is included in the command section for older systems but will not be
covered here. The two newer commands are very similar, but some of the organization of the
rules they use is different. The firewalling facilities built into the 2.4 kernel are also designed
to be extensible. If there is some function missing from the implementation, you could add it.
See the "Linux netfilter Hacking HOWTO" for details on how to do this.

Most distributions come with all the firewall support already built into the kernel, but if it is
not built into yours, you need to compile firewall support into the kernel by running make
config with the 2.2 kernel and selecting all of the following networking options:

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l Network firewalls

l TCP/ IP networking
l IP: firewalling

If you want to support a transparent proxy service on your firewall, select the following
option:

l IP: transparent proxy support

If you want your firewall to support masquerading, select the following options as well:
l IP: masquerading

l IP: ICMP masquerading

With the 2.4 kernel, you will need to select these options:
l Network packet filtering (replaces ipchains)

l IP tables support (required for filtering/ masq/ NAT)
l Packet filtering

There are several extended target and matching rule modules you may wish to compile as
well. The behavior of those extension modules is described under the iptables command. If
you have an existing firewall designed for the 2.2 kernel, or the 2.0 kernel, you can compile
support for these older-style commands and use them with your new kernel instead of the
newer iptables style of netfiltering.

The firewalling facility provides built-in rule sets, or chains, against which each network
packet is checked. In the 2.4 kernel, these chains are also organized into tables that separate
out filtering functions from masquerading and packet mangling functions. In either kernel, if a
match is found, the counters on that rule are incremented and any target for that rule is
applied. A target might accept, reject, or masquerade a packet or even pass it along to another
chain for processing. Details on the chains provided in both iptables and ipchains can be
found under the description of the appropriate command.

In addition to these chains, you can create your own user-defined chains. You might want a
special chain for your PPP interfaces or for packets from a particular site. To call a user-defined
chain, you just make it the target for a match.

It is possible to make it through a chain without matching any rules that have a target. If no
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rule matches the packet in a user-defined chain, control returns to the chain from which it was
called, and the next rule in that chain is checked. If no rule matches the packet in a built-in
chain a default policy for that chain is used. The default policy can be any of the special
targets that determine what is done with a packet. The valid targets for each command are
detailed in the commands section.

In the 2.2 kernel, you use the ipchains command to define the rules. Once you have the rules
defined, you can use ipchains-save to create a file with all the rule definitions and ipchains-restore
to restore those definitions when you reboot. The equivalent 2.4 kernel command for
defining rules is iptables. iptables-save and iptables-restore were not completed at the time
of this writing but should work similarly to their ipchains counterparts.

For more information on the kinds of decisions you need to make and the considerations that
go into defining the rules, see a general book on firewalls such as the O'Reilly book Building
Internet Firewalls by D. Brent Chapman and Elizabeth D. Zwicky. For more details on
ipchains or iptables, consult the Linux Network Administrator's Guide, 2d ed. by Olaf Kirch
and Terry Dawson, or consult one of the relevant HOW-TOs, such as the "Linux IPCHAINS
HOW-TO" or the "Linux IPTABLES HOW-TO."

2.3. Overview of TCP/ IP 2.5. Overview of NFS
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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2.5. Overview of NFS
The Network File System (NFS) is a distributed filesystem that allows users to mount remote
filesystems as if they were local. NFS uses a client-server model, in which a server exports
directories to be shared, and clients mount the directories to access the files in them. NFS
eliminates the need to keep copies of files on several machines by letting the clients all share a
single copy of a file on the server. NFS is an RPC-based application-level protocol. For more
information on the architecture of network protocols, see Section 2.3, "Overview of TCP/ IP"

earlier in this chapter.

2.5.1. Administering NFS
Setting up NFS clients and servers involves starting the NFS daemons, exporting filesystems
from the NFS servers, and mounting them on the clients. The /etc/ exports file is the NFS
server configuration file; it controls which files and directories are exported and what kinds of
access are allowed. Names and addresses for clients receiving services are kept in the
/etc/ hosts file.

2.5.2. Daemons
NFS server daemons, called nfsd daemons, run on the server and accept RPC calls from
clients. NFS servers also run the mountd daemon to handle mount requests. On the client,
caching and buffering are handled by biod, the block I/ O daemon. The portmap daemon
maps RPC program numbers to the appropriate TCP/ IP port numbers.

2.5.3. Exporting Filesystems
To set up an NFS server, first check that all the hosts that will mount your filesystem can
reach your host. Next, edit the /etc/ exports file to include the mount-point pathname of the
filesystem to be exported. If you are running mountd, the files will be exported as the
permissions in /etc/ exports allow.

2.5.4. Mounting Filesystems

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To enable an NFS client, mount a remote filesystem after NFS is started, either by using the
mount command or by specifying default remote filesystems in /etc/ fstab. A mount request
calls the server's mountd daemon, which checks the access permissions of the client and
returns a pointer to a filesystem. Once a directory is mounted, it remains attached to the local
filesystem until it is dismounted with the umount command or until the local system is
rebooted.

Usually, only a privileged user can mount filesystems with NFS. However, you can enable
users to mount and unmount selected filesystems using the mount and umount commands if
the user option is set in /etc/ fstab. This can reduce traffic by having filesystems mounted only
when needed. To enable user mounting, create an entry in /etc/ fstab for each filesystem to be
mounted.

2.4. Overview of Firewalls
and Masquerading
2.6. Overview of NIS

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2.6. Overview of NIS
The Network Information System (NIS) refers to the service formerly known as Sun Yellow
Pages (YP). It is used to make configuration information consistent on all machines in a
network. It does this by designating a single host as the master of all the system
administration files and databases and distributing this information to all other hosts on the
network. The information is compiled into databases called maps. NIS is built on the RPC
protocol. There are currently two NIS servers freely available for Linux, yps and ypserv.

2.6.1. Servers
In NIS, there are two types of servers --master and slave servers. Master servers are
responsible for maintaining the maps and distributing them to the slave servers. The files are
then available locally to requesting processes.

2.6.2. Domains
An NIS domain is a group of hosts that use the same set of maps. The maps are contained in a
subdirectory of /var/ yp having the same name as the domain. The machines in a domain share
password, hosts, and group file information. NIS domain names are set with the domainname
command.

2.6.3. NIS Maps
NIS stores information in database files called maps. Each map consists of a pair of dbm
database files, one containing a directory of keys (a bitmap of indices), and the other
containing data values. The non-ASCII structure of dbm files necessitates using NIS tools
such as yppush to move maps between machines.

The file /var/ yp/ YP_ MAP_ X_ LATE contains a complete listing of active NIS maps as well as
NIS aliases for NIS maps. All maps must be listed here in order for NIS to serve them.

2.6.4. Map Manipulation Utilities

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The following utilities are used to administer NIS maps:

makedbm
Make dbm files. Modify only ypservers map and any nondefault maps.
ypinit
Build and install NIS databases. Manipulate maps when NIS is being initialized.
Should not be used when NIS is already running.

yppush
Transfer updated maps from the master server.

2.5. Overview of NFS 2.7. Administering NIS
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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2.7. Administering NIS
NIS is enabled by setting up NIS servers and NIS clients. The descriptions given here describe
NIS setup using ypserv, which does not support a master/ slave server configuration. All NIS
commands depend on the RPC portmap program, so make sure it is installed and running
before setting up NIS.

2.7.1. Setting up an NIS server
Setting up an NIS server involves:
1. Setting a domain name for NIS using domainname
2. Editing the ypMakefile, which identifies which databases to build and what sources to
use in building them

3. Copying the ypMakefile to /var/ yp/ Makefile
4. Running make from the /var/ yp directory, which builds the databases and initializes
the server

5. Starting ypserv, the NIS server daemon

2.7.2. Setting up an NIS client
Setting up an NIS client involves setting the domain name for NIS using domainname, which
should be the same name used by the NIS server, and running ypbind.

2.7.3. NIS User Accounts
NIS networks have two kinds of user accounts: distributed and local. Distributed accounts
must be administered from the master machine; they provide information that is uniform on
each machine in an NIS domain. Changes made to distributed accounts are distributed via NIS
maps. Local accounts are administered from the local computer; they provide account

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information unique to a specific machine. They are not affected by NIS maps, and changes
made to local accounts do not affect NIS. When NIS is installed, preexisting accounts default
to local accounts.

2.6. Overview of NIS 2.8. RPC and XDR
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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2.8. RPC and XDR
RPC (Remote Procedure Call) is the session protocol used by both NFS and NIS. It allows a
host to make a procedure call that appears to be local but is really executed remotely on
another machine on the network. 11 RPC is implemented as a library of procedures, plus a
network standard for ordering bytes and data structures called XDR (eXternal Data
Representation).

2.7. Administering NIS 3. Linux Commands
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Linux in a Nutshell, 3rd
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Chapter 3. Linux Commands
Contents:
Alphabetical Summary of Commands

This chapter presents the Linux user, programmer, and system administration commands. Each entry is labeled with the command
name on the outer edge of the page. The syntax line is followed by a brief description and a list of available options. Many commands
come with examples at the end of the entry. If you need only a quick reminder or suggestion about a command, you can skip directly
to the examples.

Typographic conventions for describing command syntax are listed in the Preface. For help in locating commands, see the index at the
back of this book.

We've tried to be as thorough as possible in listing options. The basic command information and most options should be correct;
however, there are many Linux distributions and many versions of commands. New options are added and sometimes old options are
dropped. You may, therefore, find some differences between the options you find described here and the ones on your system. When
there seems to be a discrepancy, check the manpage. For most commands you can also use the option --help to get a brief usage
message. (Even when it isn't a valid option, it will usually result in an "invalid option" error along with the usage message.)

Traditionally, commands take single-letter options preceded by a single hyphen, like -d. A more recent convention allows long options
preceded by two hyphens, like --debug. Often, a feature can be invoked through either the old style or the new style of options.

3.1. Alphabetical Summary of Commands
agetty agetty [options] port baudrate [term]
System administration command. The Linux version of getty. Set terminal type, modes, speed, and line
discipline. agetty is invoked by init. It is the second process in the series init-getty-login-shell, which ultimately
connects a user with the Linux system. agetty reads the user's login name and invokes the login command with
the user's name as an argument. While reading the name, agetty attempts to adapt the system to the speed and
type of device being used.

You must specify a port, which agetty will search for in the /dev directory. You may use -, in which case agetty
reads from standard input. You must also specify baudrate, which may be a comma-separated list of rates,
through which agetty will step. Optionally, you may specify the term, which is used to override the TERM
environment variable.

Options
-h
Specify hardware, not software, flow control.
-i
Suppress printing of /etc/ issue before printing the login prompt.
-l program
Specify the use of program instead of /bin/ login.
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-m
Attempt to guess the appropriate baud rate.
-t timeout
Specify that agetty should exit if the open on the line succeeds and there is no response to the login
prompt in timeout seconds.

-L
Do not require carrier detect; operate locally only. Use this when connecting terminals.

apmd apmd [options]
System administration command. apmd handles events reported by the Advanced Power Management BIOS
driver. The driver reports on battery level and requests to enter sleep or suspend mode. apmd will log any
reports it gets via syslogd and take steps to make sure that basic sleep and suspend requests are handled
gracefully. You can fine-tune the behavior of apmd by specifying an apmd_ proxy command to run when it
receives an event.

Options
-c n, --check n
Set the number of seconds to wait for an event before rechecking the power level. Default is to wait
indefinitely. Setting this causes the battery levels to be checked more frequently.

-P command, --apmd_ prxy command
Specify the apmd_ proxy command to run when APM driver events are reported. This is generally a shell
script. The command will be invoked with parameters indicating what kind of event was received. The
parameters are in the next list.

-p n, --percentage n
Log information whenever the power changes by n percent. The default is 5. Values greater than 100 will
disable logging of power changes.

-V, --version
Print version and exit.
-v, --version
Verbose mode; all events are logged.
-W, --wall
Use wall to alert all users of a low battery status.
-w n, --warn n
Log a warning at ALERT level when the battery charge drops below n percent. The default is 10.
Negative values disable low battery level warnings.

-q, --quiet
Disable low battery level warnings.

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-?, --help
Print help summary and exit.
Parameters
The apmd proxy script will be invoked with the following parameters:
start
Invoked when the daemon starts.
stop
Invoked when the daemon stops.
suspend [ system | user ]
Invoked when a suspend request has been made. The second parameter indicates whether the request was
made by the system or by the user.

standby [ system | user ]
Invoked when a standby request has been made. The second parameter indicates whether the request was
made by the system or by the user.

resume [ suspend | standby | critical ]
Invoked when the system resumes normal operation. The second parameter indicates the mode the system
was in before resuming. (critical suspends indicate an emergency shutdown. After a critical suspend the
system may be unstable and you can use the resume command to help you recover from the suspension.

change power
Invoked when system power is changed from AC to battery or from battery to AC.
change battery
Invoked when the APM BIOS driver reports that the battery is low.
change capability
Invoked when the APM BIOS driver reports some hardware that affects its capability has been added or
removed.

apropos apropos string ...
Search the short manual page descriptions in the whatis database for occurrences of each string and display the
result on the standard output. Like whatis, except that it searches for strings instead of words. Equivalent to man
-k.

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ar ar [-V] key [args] [posname] archive [files]
Maintain a group of files that are combined into a file archive. Used most commonly to create and update library
files as used by the link editor (ld). Only one key letter may be used, but each can be combined with additional
args (with no separations between). posname is the name of a file in archive. When moving or replacing files,
you can specify that they be placed before or after posname. -V prints the version number of ar on standard
error.

Key
d
Delete files from archive.
m
Move files to end of archive.
p
Print files in archive.
q
Append files to archive.
r
Replace files in archive.
t
List the contents of archive or list the named files.
x
Extract contents from archive or only the named files.
Arguments
a
Use with r or m key to place files in the archive after posname.
b
Same as a but before posname.
c
Create archive silently.
f
Truncate long filenames.
i
Same as b.

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l

For backward compatibility; meaningless in Linux.
o
Preserve original timestamps.
s
Force regeneration of archive symbol table (useful after running strip).
S
Do not regenerate symbol table.
u
Use with r to replace only files that have changed since being put in archive.
v
Verbose; print a description of actions taken.
Example
Replace mylib. a with object files from the current directory:
ar r mylib. a `ls *. o

arch arch
Print machine architecture type to standard output. Equivalent to uname -m.

arp arp [options]
TCP/ IP command. Clear, add to, or dump the kernel's ARP cache (/ proc/ net/ arp).
Options
-v
Verbose mode.
-t type
Search for type entries when examining the ARP cache. type must be ether (Ethernet) or ax25 (AX. 25
packet radio); ether is the default.

-a [hosts]
Display hosts' entries or, if none are specified, all entries.
-d host
Remove host's entry.
-s host hardware-address

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Add the entry host hardware-address, where ether class addresses are 6 hexadecimal bytes, colon-separated.

-f file
Read entries from file and add them.

as as [options] files
Generate an object file from each specified assembly language source file. Object files have the same root name
as source files but replace the .s suffix with .o. There may be some additional system-specific options.

Options
--[ | files]
Read input files from standard input, or from files if the pipe is used.
-a[ dhlns][= file]
With only the -a option, list source code, assembler listing, and symbol table. The other options specify
additional things to list or omit:

-ad
Omit debugging directives.
-ah
Include the high-level source code, if available.
-al
Include an assembly listing.
-an
Suppress forms processing.
-as
Include a symbol listing.
=file
Set the listing filename to file.
-defsym symbol= value
Define the symbol to have the value value, which must be an integer.
-f
Skip preprocessing.
--gstabs
Generate stabs debugging information.
-o objfile

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Place output in object file objfile (default is file. o).
-v
Display the version number of the assembler.
-I path
Include path when searching for .include directives.
-K
Warn before altering difference tables.
-L
Do not remove local symbols, which begin with L.
-R
Combine both data and text in text section.
-W
Quiet mode.

at at [options] time
Execute commands at a specified time and optional date. The commands are read from standard input or from a
file. (See also batch.) End input with EOF. time can be formed either as a numeric hour (with optional minutes
and modifiers) or as a keyword. It can contain an optional date, formed as a month and date, a day of the week,
or a special keyword (today or tomorrow). An increment can also be specified.

The at command can always be issued by a privileged user. Other users must be listed in the file /etc/ at. allow if
it exists; otherwise, they must not be listed in /etc/ at. deny. If neither file exists, only a privileged user can issue
the command.

Options
-c job [job...]
Display the specified jobs on the standard output. This option does not take a time specification.
-d job [job...]
Delete the specified jobs. Same as atrm.
-f file
Read job from file, not standard input.
-l
Report all jobs that are scheduled for the invoking user. Same as atq.
-m
Mail user when job has completed, regardless of whether output was created.

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-q letter

Place job in queue denoted by letter, where letter is any single letter from a-z or A-Z. Default queue is a.
(The batch queue defaults to b.) Higher-lettered queues run at a lower priority.

-V
Display the version number.
Time
hh: mm [modifiers]
Hours can have one digit or two (a 24-hour clock is assumed by default); optional minutes can be given
as one or two digits; the colon can be omitted if the format is h, hh, or hhmm; (e. g., valid times are 5,
5: 30, 0530, 19: 45). If modifier am or pm is added, time is based on a 12-hour clock. If the keyword zulu
is added, times correspond to Greenwich Mean Time.

midnight | noon | teatime | now
Use any one of these keywords in place of a numeric time. teatime translates to 4: 00 p. m.; now must be
followed by an increment.

Date
month num[, year]
month is one of the 12 months, spelled out or abbreviated to its first three letters; num is the calendar date
of the month; year is the four-digit year. If the given month occurs before the current month, at schedules
that month next year.

day
One of the seven days of the week, spelled out or abbreviated to its first three letters.
today | tomorrow
Indicate the current day or the next day. If date is omitted, at schedules today when the specified time
occurs later than the current time; otherwise, at schedules tomorrow.

Increment
Supply a numeric increment if you want to specify an execution time or day relative to the current time. The
number should precede any of the keywords minute, hour, day, week, month, or year (or their plural forms).
The keyword next can be used as a synonym of + 1.

Examples
Note that the first two commands are equivalent:
at 1945 pm December 9 at 7: 45pm Dec 9 at 3 am Saturday at now + 5 hours at noon next day

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atq atq [options]
List the user's pending jobs, unless the user is a privileged user; in that case, everybody's jobs are listed. Same as
at -l.

Options
-q queue
Query only the specified queue and ignore all other queues.
-v
Show jobs that have completed but not yet been deleted.
-V
Print the version number.

atrm atrm [options] job [job...]
Delete jobs that have been queued for future execution. Same as at -d.
Options
-q queue
Remove job from the specified queue.
-V
Print the version number and then exit.

badblocks badblocks [options] device block-count
System administration command. Search device for bad blocks. You must specify the number of blocks on the
device (block-count).

Options
-b blocksize
Expect blocksize-byte blocks.
-o file
Direct output to file.
-v
Verbose mode.
-w
Test by writing to each block and then reading back from it.

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banner banner [option] [characters]
Print characters as a poster. If no characters are supplied, banner prompts for them and reads an input line from
standard input. By default, the results go to standard output, but they are intended to be sent to a printer.

Option
-w width
Set width to width characters. Note that if your banner is in all lowercase, it will be narrower than width
characters. If -w is not specified, the default width is 132. If -w is specified but width is not provided, the
default is 80.

Example
/usr/ games/ banner -w50 Happy Birthday! |lpr

basename basename name [suffix]
basename option
Remove leading directory components from a path. If suffix is given, remove that also. The result is printed to
standard output.

Options
--help
Print help message and then exit.
--version
Print the version number and then exit.
Examples
% basename /usr/ lib/ libm. alibm. a

% basename /usr/ lib/ libm. a .alibm

batch batch [options] [time]
Execute commands entered on standard input. If time is omitted, execute them when the system load permits
(when the load average falls below 0.8). Very similar to at, but does not insist that the execution time be entered
on the command line. See at for details.

Options
-f file
Read job from file, not standard input.
-m
Mail user when job has completed, regardless of whether output was created.
-q letter

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Place job in queue denoted by letter, where letter is one letter from a-z or A-Z. The default queue is a.
(The batch queue defaults to b.) Higher-lettered queues run at a lower priority.

-V
Print the version number and then exit.
-v
Display the time a job will be executed.

bash bash [options] [file [arguments;]]
sh [options] [file [arguments]]
Standard Linux shell, a command interpreter into which all other commands are entered. For more information,
see Chapter 7, "bash: The Bourne-Again Shell".

bc bc [options] [files]
bc is a language (and compiler) whose syntax resembles that of C, but with unlimited-precision arithmetic. bc
consists of identifiers, keywords, and symbols, which are briefly described in the following entries. Examples
are given at the end.

Interactively perform arbitrary-precision arithmetic or convert numbers from one base to another. Input can be
taken from files or read from the standard input. To exit, type quit or EOF.

Options
-l, --mathlib
Make functions from the math library available.
-s, --standard
Ignore all extensions, and process exactly as in POSIX.
-w, --warn
When extensions to POSIX bc are used, print a warning.
-q, --quiet
Do not display welcome message.
-v, --version
Print version number.
Identifiers
An identifier is a series of one or more characters. It must begin with a lowercase letter but may also contain
digits and underscores. No uppercase letters are allowed. Identifiers are used as names for variables, arrays, and
functions. Variables normally store arbitrary-precision numbers. Within the same program you may name a
variable, an array, and a function using the same letter. The following identifiers would not conflict:

x
Variable x.

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x[ i]
Element i of array x. i can range from 0 to 2047 and can also be an expression.
x( y, z)
Call function x with parameters y and z.
Input-output keywords
ibase, obase, scale, and last store a value. Typing them on a line by themselves displays their current value. You
can also change their values through assignment. The letters A-F are treated as digits whose values are 10-15.

ibase = n
Numbers that are input (e. g., typed) are read as base n (default is 10).
obase = n
Numbers that are displayed are in base n (default is 10). Note: Once ibase has been changed from 10, use
A to restore ibase or obase to decimal.

scale = n
Display computations using n decimal places (default is 0, meaning that results are truncated to integers).
scale is normally used only for base-10 computations.

last
Value of last printed number.
Statement keywords
A semicolon or a newline separates one statement from another. Curly braces are needed when grouping
multiple statements.

if (rel-expr) {statements} [else {statements}]
Do one or more statements if relational expression rel-expr is true. Otherwise, do nothing, or if else (an
extension) is specified, do alternative statements. For example:

if( x== y) {i = i + 1} else {i = i -1}while (rel-expr) {statements}
Repeat one or more statements while rel-expr is true; for example:
while( i> 0) {p = p* n; q = a/ b; i = i-1}for (expr1; rel-expr; expr2) {statements}
Similar to while; for example, to print the first 10 multiples of 5, you could type:
for( i= 1; i<= 10; i++) i* 5GNU bf does not require three arguments to for. A missing argument 1 or 3 means that those expressions will
never be evaluated. A missing argument 2 evaluates to the value 1.

break

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Terminate a while or for statement.

print list
GNU extension. It provides an alternate means of output. list consists of a series of comma-separated
strings and expressions; print displays these entities in the order of the list. It does not print a newline
when it terminates. Expressions are evaluated, printed, and assigned to the special variable last. Strings
(which may contain special characters, i. e., characters beginning with \) are simply printed. Special
characters can be:

a
Alert or bell
b
Backspace
f
Form feed
n
Newline
r
Carriage return
q
Double quote
t
Tab
\
Backslash
continue
GNU extension. When within a for statement, jump to the next iteration.
halt
GNU extension. Cause the bc processor to quit.
limits
GNU extension. Print the limits enforced by the local version of bc.
Function keywords
define f( args) {
Begin the definition of function f having the arguments args. The arguments are separated by commas.
Statements follow on successive lines. End with a }.

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auto x, y

Set up x and y as variables local to a function definition, initialized to 0 and meaningless outside the
function. Must appear first.

return( expr)
Pass the value of expression expr back to the program. Return 0 if (expr) is left off. Used in function
definitions.

sqrt( expr)
Compute the square root of expression expr.
length( expr)
Compute how many significant digits are in expr.
scale( expr)
Same as length, but count only digits to the right of the decimal point.
read( )
GNU extension. Read a number from standard input. Return value is the number read, converted via the
value of ibase.

Math library functions
These are available when bc is invoked with -l. Library functions set scale to 20.
s( angle)
Compute the sine of angle, a constant or expression in radians.
c( angle)
Compute the cosine of angle, a constant or expression in radians.
a( n)
Compute the arctangent of n, returning an angle in radians.
e( expr)
Compute e to the power of expr.
l( expr)
Compute the natural log of expr.
j( n, x)
Compute the Bessel function of integer order n.
Operators
These consist of operators and other symbols. Operators can be arithmetic, unary, assignment, or relational:
arithmetic

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+ -* / % ^

unary
-++ --
assignment
=+ =-=* =/ =% =^ =
relational
< <= > >= == !=
Other symbols
/* */
Enclose comments.
()
Control the evaluation of expressions (change precedence). Can also be used around assignment
statements to force the result to print.

{}
Use to group statements.
[]
Indicate array index.
"text"
Use as a statement to print text.
Examples
Note in these examples that when you type some quantity (a number or expression), it is evaluated and printed,
but assignment statements produce no display.

ibase = 8 Octal input20 Evaluate this octal number 16 Terminal displays decimal valueobase = 2 Display output in base 2 instead of base 1020 Octal input 10000 Terminal now displays binary valueibase = A Restore base-10 inputscale = 3 Truncate results to 3 decimal places8/ 7 Evaluate a division 1.001001000 Oops! Forgot to reset output base to 10obase= 10 Input is decimal now, so A isn't needed8/ 71.142 Terminal displays result (truncated)

The following lines show the use of functions:
define p( r, n){ Function p uses two argumentsauto v v is a local variablev = r^ n r raised to the n powerreturn( v)} Value returned

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scale= 5 x= p( 2.5,2)x = 2.5 ^ 2x Print value of x 6.25length( x) Number of digits 3scale( x) Number of places right of decimal point 2

biff biff [arguments]
Notify user of mail arrival and sender's name. biff operates asynchronously. Mail notification works only if your
system is running the comsat( 8) server. The command biff y enables notification, and the command biff n
disables notification. With no arguments, biff reports biff's current status.

bison bison [options] file
Given a file containing context-free grammar, convert into tables for subsequent parsing while sending output to
file. c. This utility is both to a large extent compatible with yacc and named for it. All input files should use the
suffix .y; output files will use the original prefix. All long options (those preceded by --) may instead be
preceded by +.

Options
-b prefix, --file-prefix= prefix
Use prefix for all output files.
-d, --defines
Generate file. h, producing #define statements that relate bison's token codes to the token names declared
by the user.

-r, --raw
Use bison token numbers, not yacc-compatible translations, in file. h.
-k, --token-table
Include token names and values of YYNTOKENS, YYNNTS, YYNRULES, and YYNSTATES in file. c.
-l, --no-lines
Exclude #line constructs from code produced in file. c. (Use after debugging is complete.)
-n, --no-parser
Suppress parser code in output, allowing only declarations. Assemble all translations into a switch
statement body and print it to file. act.

-o file, --output-file= file
Output to file.
-p prefix, --name-prefix= prefix
Substitute prefix for yy in all external symbols.
-t, --debug

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Compile runtime debugging code.
-v, --verbose
Verbose mode. Print diagnostics and notes about parsing tables to file. output.
-V, --version
Display version number.
-y, --yacc, --fixed-output-files
Duplicate yacc's conventions for naming output files.

bootpd bootpd [options] [configfile [dumpfile] ]
TCP/ IP command. Internet Boot Protocol server. bootpd normally is run by /etc/ inetd by including the following
line in the file /etc/ inetd. conf:

bootps dgram udp wait root /etc/ bootpd bootpdThis causes bootpd to be started only when a boot request arrives. It may also be started in standalone mode,
from the command line. Upon startup, bootpd first reads its configuration file, /etc/ bootptab (or the configfile
listed on the command line), then begins listening for BOOTREQUEST packets.

bootpd looks in /etc/ services to find the port numbers it should use. Two entries are extracted: bootps --the
bootp server listening port --and bootpc --the destination port used to reply to clients.

If bootpd is compiled with the -DDEBUG option, receipt of a SIGUSR1 signal causes it to dump its memory-resident
database to the file /etc/ bootpd. dump or the command-line specified dumpfile.

Options
-c directory
Force bootpd to work in directory.
-d level
Specify the debugging level. Omitting level will increment the level by 1.
-t timeout
Specify a timeout value in minutes. A timeout value of 0 means wait forever.
Configuration file
The bootpd configuration file has a format in which two-character, case-sensitive tag symbols are used to
represent host parameters. These parameter declarations are separated by colons. The general format is:

hostname: tg= value: tg= value: tg= valuewhere hostname is the name of a bootp client and tg is a tag symbol. The currently recognized tags are listed
next.

Tags

Tag Meaning
bf Bootfile

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bs Bootfile size in 512-octet blocks
cs Cookie server address list
ds Domain name server address list
gw Gateway address list
ha Host hardware address
hd Bootfile home directory
hn Send hostname
ht Host hardware type (see Assigned Numbers RFC)
im Impress server address list
ip Host IP address
lg Log server address list
lp lpr server address list
ns IEN-116 name server address list
rl Resource location protocol server address list
sm Host subnet mask
tc Table continuation
to Time offset in seconds from UTC
ts Time server address list
vm Vendor magic cookie selector

There is also a generic tag, Tn, where n is an RFC 1048 vendor field tag number. Generic data may be
represented as either a stream of hexadecimal numbers or as a quoted string of ASCII characters.

bootpgw bootpgw [options] server
Internet Boot Protocol Gateway. Maintain a gateway that forwards bootpd requests to server. In addition to
dealing with BOOTREPLY packets, also deal with BOOTREQUEST packets. bootpgw is normally run by
/etc/ inetd by including the following line in the file /etc/ inetd. conf:

bootps dgram udp wait root /etc/ bootpgw bootpgwThis causes bootpgw to be started only when a boot request arrives. bootpgw takes all the same options as
bootpd, except -c.

bootptest bootptest [options] server [template]
TCP/ IP command. Test server's bootpd daemon by sending requests every second for 10 seconds or until the
server responds. Read options from the template file, if provided.

Options
-f file
Read the boot filename from file.
-h
Identify client by hardware, not IP, address.
-m magic-number
Provide magic-number as the first word of the vendor options field.

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bzip2 bzip2 [options] filenames
bunzip2 [options] filenames
bzcat [option] filenames
bzip2recover filenames
File compression and decompression utility similar to gzip, but uses a different algorithm and encoding method
to get better compression. bzip2 replaces each file in filenames with a compressed version of the file and with a
.bz2 extension appended. bunzip2 decompresses each file compressed by bzip2 (ignoring other files, except to
print a warning). bzcat decompresses all specified files to standard output, and bzip2recover is used to try to
recover data from damaged files.

Options
--
End of options; treat all subsequent arguments as filenames.
-dig
Set block size to dig � 100KB when compressing, where dig is a single digit from 1 to 9.
-c, --stdout
Compress or decompress to standard output.
-d, --decompress
Force decompression.
-f, --force
Force overwrite of output files. Default is not to overwrite. Also forces breaking of hard links to files.
-k, --keep
Keep input files; don't delete them.
-L, --license, -V, --version
Print license and version information and exit.
-q, --quiet
Quiet. Print only critical messages.
-s, --small
Use less memory, at the expense of speed.
-t, --test
Check the integrity of the files, but don't actually compress them.
-v, --verbose
Verbose. Show the compression ratio for each file processed. Add more -v's to increase the verbosity.

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-z, --compress

Forces compression, even if invoked as bunzip2 or bzcat.
--repetitive-fast, --repetitive-best
Sometimes useful in versions earlier than 0.9.5 (which has an improved sorting algorithm) for providing
some control over the algorithm.

c++ c++ [options] files
See g++.

cal cal [-jy] [[ month] year]
Print a 12-month calendar (beginning with January) for the given year or a one-month calendar of the given
month and year. month ranges from 1 to 12. year ranges from 1 to 9999. With no arguments, print a calendar for
the current month.

Options
-j
Display Julian dates (days numbered 1 to 365, starting from January 1).
-m
Display Monday as the first day of the week.
-y
Display entire year.
Examples
cal 12 1995 cal 1994 > year_ file

cardctl cardctl [options] command
System administration command. Control PCMCIA sockets or select the current scheme. The current scheme is
sent along with the address of any inserted cards to configuration scripts (by default located in /etc/ pcmcia). The
scheme command displays or changes the scheme. The other commands operate on a named card socket number
or, if no number is given, all sockets.

Commands
config [socket]
Display current socket configuration.
eject [socket]
Prepare the system for the card( s) to be ejected.
ident [socket]
Display card identification information.

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insert [socket]

Notify system that a card has been inserted.
reset [socket]
Send reset signal to card.
resume [socket]
Restore power to socket and reconfigure for use.
scheme [name]
Display current scheme or change to specified scheme name.
status [socket]
Display current socket status.
suspend [socket]
Shut down device and cut power to socket.
Options
-c directory
Look for card configuration information in directory instead of /etc/ pcmcia.
-f file
Use file to keep track of the current scheme instead of /var/ run/ pcmcia-scheme.
-s file
Look for current socket information in file instead of /var/ run/ stab.

cardmgr cardmgr [options]
System administration command. The PCMCIA card daemon. cardmgr monitors PCMCIA sockets for devices
that have been added or removed. When a card is detected, it attempts to get the card's ID and configure it
according to the card configuration database (usually stored in /etc/ pcmcia/ config). By default, cardmgr both
creates a system log entry when it detects cards and beeps. Two high beeps mean it successfully identified and
configured a device. One high beep followed by one low beep means it identified the device, but was unable to
configure it successfully. One low beep means it could not identify the inserted card. Information on the
currently configured cards can be found in /var/ run/ stab.

Options
-cdirectory
Look in directory for the card configuration database instead of /etc/ pcmcia.
-d
use modprobe instead of insmod to load the PCMCIA device driver.
-f

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Run in the foreground to process the current cards, then run as a daemon.

-mdirectory
Look in directory for card device modules instead of /lib/ modules/ `uname -r`.
-o
Configure the cards present in one pass, then exit.
-pfile
Write cardmgr's process ID to file instead of /var/ run/ cardmgr. pid.
-q
Run in quiet mode. No beeps.
-sfile
Write current socket information to file instead of /var/ run/ stab.
-v
Verbose mode.
-V
Print version number and exit.

cat cat [options] [files]
Read (concatenates) one or more files and print them on standard output. Read standard input if no files are
specified or if -is specified as one of the files; input ends with EOF. You can use the > operator to combine
several files into a new file or >> to append files to an existing file.

Options
-A, --show-all
Same as -vET.
-b, --number-nonblank
Number all nonblank output lines, starting with 1.
-e
Same as -vE.
-E, --show-ends
Print $ at the end of each line.
-n, --number
Number all output lines, starting with 1.
-s, --squeeze-blank

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Squeeze down multiple blank lines to one blank line.

-t
Same as -vT.
-T, --show-tabs
Print TAB characters as ^I.
-u
Ignored; retained for Unix compatibility.
-v, --show-nonprinting
Display control and nonprinting characters, with the exception of LINEFEED and TAB.
Examples
cat ch1 Display a filecat ch1 ch2 ch3 > all Combine filescat note5 >> notes Append to a filecat > temp1 Create file at terminal; end with EOFcat > temp2 << STOP Create file at terminal; end with STOP

cc cc [options] files
See gcc.

cpp cpp [options] [ ifile [ ofile ] ]
GNU C language preprocessor. cpp is invoked as the first pass of any C compilation by the gcc command. The
output of cpp is a form acceptable as input to the next pass of the C compiler, and cpp normally invokes gcc
after it finishes processing. ifile and ofile are, respectively, the input and output for the preprocessor; they default
to standard input and standard output.

Options
-$
Do not allow $ in identifiers.
-dM
Suppress normal output. Print series of #defines that create the macros used in the source file.
-dD
Similar to -dM but exclude predefined macros and include results of preprocessing.
-idirafter dir
Search dir for header files when a header file is not found in any of the included directories.
-imacros file
Process macros in file before processing main files.

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-include file

Process file before main file.
-iprefix prefix
When adding directories with -iwithprefix, prepend prefix to the directory's name.
-iwithprefix dir
Append dir to the list of directories to be searched when a header file cannot be found in the main include
path. If -iprefix has been set, prepend that prefix to the directory's name.

-lang-c, -lang-c++, -lang-objc, -lang-objc++
Expect the source to be in C, C++, Objective C, or Objective C++, respectively.
-lint
Display all lint commands in comments as #pragma lint command.
-nostdinc
Search only specified, not standard, directories for header files.
-nostdinc++
Suppress searching of directories believed to contain C++-specific header files.
-pedantic
Warn verbosely.
-pedantic-errors
Produce a fatal error in every case in which -pedantic would have produced a warning.
-traditional
Behave like traditional C, not ANSI.
-undef
Suppress definition of all nonstandard macros.
-Aname[= def]
Assert name with value def as if defined by a #assert.
-C
Pass along all comments (except those found on cpp directive lines). By default, cpp strips C-style
comments.

-Dname[= def]
Define name with value def as if by a #define. If no =def is given, name is defined with value 1. -D has
lower precedence than -U.

-H

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Print pathnames of included files, one per line, on standard error.

-Idir
Search in directory dir for #include files whose names do not begin with / before looking in directories
on standard list. #include files whose names are enclosed in double quotes and do not begin with / will be
searched for first in the current directory, then in directories named on -I options, and last in directories
on the standard list.

-M [-MG]
Suppress normal output. Print a rule for make that describes the main source file's dependencies. If -MG
is specified, assume that missing header files are actually generated files, and look for them in the source
file's directory.

-MD file
Similar to -M, but output to file; also compile the source.
-MM
Similar to -M. Describe only those files included as a result of #include "file".
-MMD file
Similar to -MD, but describe only the user's header files.
-P
Preprocess input without producing line-control information used by next pass of C compiler.
-Uname
Remove any initial definition of name, where name is a reserved symbol predefined by the preprocessor
or a name defined on a -D option. Names predefined by cpp are unix and i386 (for Intel systems).

-Wcomment, -Wcomments
Warn when encountering the beginning of a nested comment.
-Wtraditional
Warn when encountering constructs that are interpreted differently in ANSI from traditional C.
Special names
cpp understands various special names, some of which are:
__ DATE__
Current date (e. g., Oct 10 1999)
__ FILE__
Current filename (as a C string)
__ LINE__
Current source line number (as a decimal integer)
__ TIME__

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Current time (e. g., 12: 00: 00)
These special names can be used anywhere, including macros, just like any other defined names. cpp's
understanding of the line number and filename may be changed using a #line directive.

Directives
All cpp directive lines start with # in column 1. Any number of blanks and tabs is allowed between the # and the
directive. The directives are:

#assert name (string)
Define a question called name, with an answer of string. Assertions can be tested with #if directives. The
predefined assertions for #system, #cpu, and #machine can be used for architecture-dependent changes.

#unassert name
Remove assertion for question name.
#define name token-string
Define a macro called name, with a value of token-string. Subsequent instances of name are replaced with
token-string.

#define name( arg, ... , arg ) token-string
This allows substitution of a macro with arguments. token-string will be substituted for name in the input
file. Each call to name in the source file includes arguments that are plugged into the corresponding args
in token-string.

#undef name
Remove definition of the macro name. No additional tokens are permitted on the directive line after
name.

#ident string
Put string into the comment section of an object file.
#include "filename", #include< filename>
Include contents of filename at this point in the program. No additional tokens are permitted on the
directive line after the final " or >.

#line integer-constant "filename"
Cause cpp to generate line-control information for the next pass of the C compiler. The compiler behaves
as if integer-constant is the line number of the next line of source code and filename (if present) is the
name of the input file. No additional tokens are permitted on the directive line after the optional filename.

#endif
End a section of lines begun by a test directive (# if, #ifdef, or #ifndef). No additional tokens are
permitted on the directive line.

#ifdef name
Lines following this directive and up to matching #endif or next #else or #elif will appear in the output if
name is currently defined. No additional tokens are permitted on the directive line after name.

#ifndef name
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Lines following this directive and up to matching #endif or next #else or #elif will appear in the output if
name is not currently defined. No additional tokens are permitted on the directive line after name.

#if constant-expression
Lines following this directive and up to matching #endif or next #else or #elif will appear in the output if
constant-expression evaluates to nonzero.

#elif constant-expression
An arbitrary number of #elif directives are allowed between an #if, #ifdef, or #ifndef directive and an
#else or #endif directive. The lines following the #elif and up to the next #else, #elif, or #endif directive
will appear in the output if the preceding test directive and all intervening #elif directives evaluate to
zero, and the constant-expression evaluates to nonzero. If constant-expression evaluates to nonzero, all
succeeding #elif and #else directives will be ignored.

#else
Lines following this directive and up to the matching #endif will appear in the output if the preceding test
directive evaluates to 0, and all intervening #elif directives evaluate to 0. No additional tokens are
permitted on the directive line.

#error
Report fatal errors.
#warning
Report warnings, but then continue processing.

cfdisk cfdisk [options] [device]
System administration command. Partition a hard disk. device may be /dev/ hda (default), /dev/ hdb, /dev/ sda,
/dev/ sdb, /dev/ sdc, or /dev/ sdd. See also fdisk.

Options
-a
Highlight the current partition with a cursor, not reverse video.
-c cylinders
Specify the number of cylinders.
-h heads
Specify the number of heads.
-s sectors
Specify the number of sectors per track.
-z
Do not read the partition table; partition from scratch.
-P format

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Display the partition table in format, which must be r (raw data), s (sector order), or t (raw format).

Commands
up arrow, down arrow
Move among partitions.
b
Toggle partition's bootable flag.
d
Delete partition (allow other partitions to use its space).
g
Alter the disk's geometry. Prompt for what to change: cylinders, heads, or sectors (c, h, or s,
respectively).

h
Help.
m
Attempt to ensure maximum usage of disk space in the partition.
n
Create a new partition. Prompt for more information.
p
Display the partition table.
q
Quit without saving information.
t
Prompt for a new filesystem type, and change to that type.
u
Change the partition size units, rotating from megabytes to sectors to cylinders and back.
W
Save information. Note that this letter must be uppercase.

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chattr chattr [options] mode files
Modify file attributes. Specific to Linux Second Extended Filesystem. Behaves similarly to symbolic chmod,
using +, -, and =. mode is in the form opcode attribute. See also lsattr.

Options
-R
Modify directories and their contents recursively.
-V
Print modes of attributes after changing them.
-v version
Set the file's version.
Opcodes
+
Add attribute.
-Remove
attribute.
=
Assign attributes (removing unspecified attributes).
Attributes
A
Don't update access time on modify.
a
Append only for writing. Can be set or cleared only by a privileged user.
c
Compressed.
d
No dump.
i
Immutable. Can be set or cleared only by a privileged user.
s
Secure deletion; the contents are zeroed on deletion.
u

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Undeletable.
S
Synchronous updates.
Examples
chattr +a myfile As superuser

chfn chfn [options] [username]
Change the information that is stored in /etc/ passwd and displayed when a user is fingered. Without options,
chfn enters interactive mode and prompts for changes. To make a field blank, enter the keyword none. Only a
privileged user can change information for another user. For regular users, chfn prompts for the user's password
before making the change.

Options
-f, --full-name
Specify new full name.
-h, --home-phone
Specify new home phone number.
-o, --office
Specify new office number.
-p, --office-phone
Specify new office phone number.
-u, --help
Print help message and then exit.
-v, --version
Print version information and then exit.
Example
chfn -f "Ellen Siever" ellen

chgrp chgrp [options] newgroup files
chgrp [options]
Change the group of one or more files to newgroup. newgroup is either a group ID number or a group name
located in /etc/ group. Only the owner of a file or a privileged user may change its group.

Options
-c, --changes
Print information about those files that are changed.

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-f, --silent, --quiet
Do not print error messages about files that cannot be changed.
--help
Print help message and then exit.
-R, --recursive
Traverse subdirectories recursively, applying changes.
--reference= filename
Change the group to that associated with filename. In this case, newgroup is not specified.
-v, --verbose
Verbosely describe ownership changes.
--version
Print version information and then exit.

chmod chmod [options] mode files
chmod [options] --reference= filename files
Change the access mode (permissions) of one or more files. Only the owner of a file or a privileged user may
change its mode. mode can be numeric or an expression in the form of who opcode permission. who is optional
(if omitted, default is a); choose only one opcode. Multiple modes may be specified, separated by commas.

Options
-c, --changes
Print information about files that are changed.
-f, --silent, --quiet
Do not notify user of files that chmod cannot change.
--help
Print help message and then exit.
-R, --recursive
Traverse subdirectories recursively, applying changes.
--reference= filename
Change permissions to those associated with filename.
-v, --verbose
Print information about each file, whether changed or not.
--version

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Print version information and then exit.
Who
u
User
g
Group
o
Other
a
All (default)
Opcode
+
Add permission.
-Remove
permission.
=
Assign permission (and remove permission of the unspecified fields).
Permissions
r
Read.
w
Write.
x
Execute.
s
Set user (or group) ID.
t
Sticky bit; save text (file) mode or prevent removal of files by nonowners (directory).
u
User's present permission.

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g

Group's present permission.
o
Other's present permission.
Alternatively, specify permissions by a three-digit octal number. The first digit designates owner permission; the
second, group permission; and the third, other's permission. Permissions are calculated by adding the following
octal values:

4
Read.
2
Write.
1
Execute.
Note: A fourth digit may precede this sequence. This digit assigns the following modes:
4
Set user ID on execution to grant permissions to process based on file's owner, not on permissions of user
who created the process.

2
Set group ID on execution to grant permissions to process based on the file's group, not on permissions of
user who created the process.

1
Set sticky bit.
Examples
Add execute-by-user permission to file:
chmod u+ x fileEither of the following will assign read/ write/ execute permission by owner (7), read/ execute permission by
group (5), and execute-only permission by others (1) to file:

chmod 751 filechmod u= rwx, g= rx, o= x file

Any one of the following will assign read-only permission to file for everyone:
chmod =r filechmod 444 filechmod a-wx, a+ r file

Set the user ID, assign read/ write/ execute permission by owner, and assign read/ execute permission by group
and others:

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chmod 4755 file

chown chown [options] newowner files
chown [options] --reference= filename files
Change the ownership of one or more files to newowner. newowner is either a user ID number or a login name
located in /etc/ passwd. chown also accepts users in the form newowner: newgroup or newowner. newgroup. The
last two forms change the group ownership as well. If no owner is specified, the owner is unchanged. With a
period or colon but no group, the group is changed to that of the new owner. Only the current owner of a file or a
privileged user may change its owner.

Options
-c, --changes
Print information about those files that are changed.
--dereference
Follow symbolic links.
-f, --silent, --quiet
Do not print error messages about files that cannot be changed.
-h, --no-dereference
Change the ownership of each symbolic link (on systems that allow it), rather than the referenced file.
-v, --verbose
Print information about all files that chown attempts to change, whether or not they are actually changed.
-R, --recursive
Traverse subdirectories recursively, applying changes.
--reference= filename
Change owner to the owner of filename instead of specifying a new owner explicitly.
--help
Print help message and then exit.
--version
Print version information and then exit.

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chpasswd chpasswd [option]
System administration command. Change user passwords in a batch. chpasswd accepts input in the form of one
username: password pair per line. If the -e option is not specified, password will be encrypted before being
stored.

Option
-e
Passwords given are already encrypted.

chroot chroot newroot [command]
System administration command. Change root directory for command or, if none is specified, for a new copy of
the user's shell. This command or shell is executed relative to the new root. The meaning of any initial / in
pathnames is changed to newroot for a command and any of its children. In addition, the initial working
directory is newroot. This command is restricted to privileged users.

chsh chsh [options] [username]
Change your login shell, interactively or on the command line. Warn if shell does not exist in /etc/ shells. Specify
the full path to the shell. chsh prompts for your password. Only a privileged user can change another user's shell.

Options
-l, --list-shells
Print valid shells, as listed in /etc/ shells, and then exit.
-s shell, --shell shell
Specify new login shell.
-u, --help
Print help message and then exit.
-v, --version
Print version information and then exit.
Example
chsh -s /bin/ tcsh

cksum cksum [files]
Compute a cyclic redundancy check (CRC) checksum for all files; used to ensure that a file was not corrupted
during transfer. Read from standard input if the character -or no files are given. Display the resulting checksum,
the number of bytes in the file, and (unless reading from standard input) the filename.

clear clear
Clear the terminal display.

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cmp cmp [options] file1 file2 [skip1 [skip2]]
Compare file1 with file2. Use standard input if file1 is -or missing. See also comm and diff. Files can be of any
type. skip1 and skip2 are optional offsets in the files at which the comparison is to start.

Options
-c, --print-chars
Print differing bytes as characters.
-i num, --ignore-initial= num
Ignore the first num bytes of input.
-l, --verbose
Print offsets and codes of all differing bytes.
-s, --quiet, --silent
Work silently; print nothing, but return exit codes:
0
Files are identical.
1
Files are different.
2
Files are inaccessible.
Example
Print a message if two files are the same (exit code is 0):
cmp -s old new && echo 'no changes'

col col [options]
A postprocessing filter that handles reverse linefeeds and escape characters, allowing output from tbl or nroff to
appear in reasonable form on a terminal.

Options
-b
Ignore backspace characters; helpful when printing manpages.
-f
Process half-line vertical motions, but not reverse line motion. (Normally, half-line input motion is
displayed on the next full line.)

-l n
Buffer at least n lines in memory. The default buffer size is 128 lines.
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-x
Normally, col saves printing time by converting sequences of spaces to tabs. Use -x to suppress this
conversion.

Examples
Run myfile through tbl and nroff, then capture output on screen by filtering through col and more:
tbl myfile | nroff | col | moreSave manpage output for the ls command in out. print, stripping out backspaces (which would otherwise appear
as ^H):

man ls | col -b > out. print

colcrt colcrt [options] [files]
A postprocessing filter that handles reverse linefeeds and escape characters, allowing output from tbl or nroff to
appear in reasonable form on a terminal. Put half-line characters (e. g., subscripts or superscripts) and underlining
(changed to dashes) on a new line between output lines.

Options
-Do
not underline.
-2
Double space by printing all half-lines.

colrm colrm [start [stop]]
Remove specified columns from a file, where a column is a single character in a line. Read from standard input
and write to standard output. Columns are numbered starting with 1; begin deleting columns at (including) the
start column, and stop at (including) the stop column. Entering a tab increments the column count to the next
multiple of either the start or stop column; entering a backspace decrements it by 1.

Example
colrm 3 5 < test1 > test2

column column [options] [files]
Format input from one or more files into columns, filling rows first. Read from standard input if no files are
specified.

Options
-c num
Format output into num columns.
-s char
Delimit table columns with char. Meaningful only with -t.

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-t

Format input into a table. Delimit with whitespace, unless an alternate delimiter has been provided with -s.

-x
Fill columns before filling rows.

comm comm [options] file1 file2
Compare lines common to the sorted files file1 and file2. Three-column output is produced: lines unique to file1,
lines unique to file2, and lines common to both files. comm is similar to diff in that both commands compare
two files. But comm can also be used like uniq; that is, comm selects duplicate or unique lines between two
sorted files, whereas uniq selects duplicate or unique lines within the same sorted file.

Options
-Read
the standard input.
-num
Suppress printing of column num. Multiple columns may be specified and should not be space-separated.
--help
Print help message and exit.
--version
Print version information and exit.
Example
Compare two lists of top-10 movies, and display items that appear in both lists:
comm -12 siskel_ top10 ebert_ top10

compress compress [options] files
Compress one or more files, replacing each with the compressed file of the same name with .Z appended. If no
file is specified, compress standard input. Each file specified is compressed separately. compress ignores files
that are symbolic links. See also gzip.

Options
-b maxbits
Limit the maximum number of bits.
-c
Write output to standard output, not to a .Z file.
-d
Decompress instead of compressing. Same as uncompress.

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-f
Force generation of an output file even if one already exists.
-r
If any of the specified files is a directory, compress recursively.
-v
Print compression statistics.
-V
Print version and compilation information and then exit.

cp cp [options] file1 file2
cp [options] files directory
Copy file1 to file2, or copy one or more files to the same names under directory. If the destination is an existing
file, the file is overwritten; if the destination is an existing directory, the file is copied into the directory (the
directory is not overwritten).

Options
-a, --archive
Preserve attributes of original files where possible. Same as -dpR.
-b, --backup
Back up files that would otherwise be overwritten.
-d, --no-dereference
Do not dereference symbolic links; preserve hard link relationships between source and copy.
-f, --force
Remove existing files in the destination.
-i, --interactive
Prompt before overwriting destination files.
-l, --link
Make hard links, not copies, of nondirectories.
-p, --preserve
Preserve all information, including owner, group, permissions, and timestamps.
-P, --parents
Preserve intermediate directories in source. The last argument must be the name of an existing directory.
For example, the command:

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cp --parents jphekman/ book/ ch1 newdircopies the file jphekman/ book/ ch1 to the file newdir/ jphekman/ book/ ch1, creating intermediate directories
as necessary.

-r, -R, --recursive
Copy directories recursively.
-S backup-suffix, --suffix= backup-suffix
Set suffix to be appended to backup files. This may also be set with the SIMPLE_ BACKUP_ SUFFIX
environment variable. The default is ~. You need to explicitly include a period if you want one before the
suffix (e. g., specify .bak, not bak).

-s, --symbolic-link
Make symbolic links instead of copying. Source filenames must be absolute.
-u, --update
Do not copy a file to an existing destination with the same or newer modification time.
-v, --verbose
Before copying, print the name of each file.
-V type, --version-control= type
Set the type of backups made. You may also use the VERSION_ CONTROL environment variable. The
default is existing. Valid arguments are:

t, numbered
Always make numbered backups.
nil, existing
Make numbered backups of files that already have them; otherwise, make simple backups.
never, simple
Always make simple backups.
-x, --one-file-system
Ignore subdirectories on other filesystems.

cpio cpio flags [options]
Copy file archives in from or out to tape or disk, or to another location on the local machine. Each of the three
flags -i, -o, or -p accepts different options.

Flags
-i, --extract [options] [patterns]
Copy in (extract) from an archive files whose names match selected patterns. Each pattern can include
Bourne shell filename metacharacters. (Patterns should be quoted or escaped so they are interpreted by

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cpio, not by the shell.) If pattern is omitted, all files are copied in. Existing files are not overwritten by
older versions from the archive unless -u is specified.

-o, --create [options]
Copy out to an archive a list of files whose names are given on the standard input.
-p, --pass-through [options] directory
Copy (pass) files to another directory on the same system. Destination pathnames are interpreted relative
to the named directory.

Comparison of valid options
Options available to the -i, -o, and -p flags are shown here. (The -is omitted for clarity):
i: bcdf mnrtsuv B SVCEHMR IFo: 0a c vABL VC HM O Fp: 0a d lm uv L V R

Options
-0, --null
Expect list of filenames to be terminated with null, not newline. This allows files with a newline in their
names to be included.

-a, --reset-access-time
Reset access times of input files after reading them.
-A, --append
Append files to an existing archive, which must be a disk file. Specify this archive with -O or -F.
-b, --swap
Swap bytes and half-words to convert between big-endian and little-endian 32-bit integers.
-B
Block input or output using 5120 bytes per record (default is 512 bytes per record).
--blocksize= size
Set input or output blocksize to size � 512 bytes.
-c
Read or write header information as ASCII characters; useful when source and destination machines are
different types.

-C n, --io-size= n
Like -B, but blocksize can be any positive integer n.
-d, --make-directories
Create directories as needed.
-E file, --pattern-file= file

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Extract filenames from the archives that match patterns in file.
-f, --nonmatching
Reverse the sense of copying; copy all files except those that match patterns.
-F file, --file= file
Use file as the archive, not stdin or stdout. file can reside on another machine, if given in the form
user@ hostname: file (where user@ is optional).

--force-local
Assume that file (provided by -F, -I, or -O) is a local file, even if it contains a colon (:) indicating a
remote file.

-H type, --format= type
Use type format. Default for copy-out is bin; for copy-in the default is autodetection of the format. Valid
formats (all caps also accepted) are:

bin
Binary
odc
Old (POSIX. 1) portable format
newc
New (SVR4) portable format
crc
New (SVR4) portable format with checksum added
tar
Tar
ustar
POSIX. 1 tar (also recognizes GNU tar archives)
hpbin
HP-UX's binary (obsolete)
hpodc
HP-UX's portable format
-I file
Read file as an input archive. May be on a remote machine (see -F).
-k
Ignored. For backward compatibility.

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-l, --link
Link files instead of copying.
-L, --dereference
Follow symbolic links.
-m, --preserve-modification-time
Retain previous file modification time.
-M msg, --message= msg
Print msg when switching media, as a prompt before switching to new media. Use variable %d in the
message as a numeric ID for the next medium. -M is valid only with -I or -O.

-n, --numeric-uid-gid
When verbosely listing contents, show user ID and group ID numerically.
--no-absolute-filenames
Create all copied-in files relative to the current directory.
--no-preserve-owner
Make all copied files owned by yourself, instead of the owner of the original. Useful only if you are a
privileged user.

-O file
Archive the output to file, which may be a file on another machine (see -F).
--only-verify-crc
For a CRC-format archive, verify the CRC of each file; don't actually copy the files in.
--quiet
Don't print the number of blocks copied.
-r
Rename files interactively.
-R [user][: group], --owner [user][: group]
Reassign file ownership and group information to the user's login ID (privileged users only).
-s, --swap-bytes
Swap bytes of each two-byte half-word.
-S, --swap-half-words
Swap half-words of each four-byte word.
--sparse

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For copy-out and copy-pass, write files that have large blocks of zeros as sparse files.

-t, --list
Print a table of contents of the input (create no files). When used with the -v option, resembles output of
ls -l.

-u, --unconditional
Unconditional copy; old files can overwrite new ones.
-v, --verbose
Print a list of filenames processed.
-V, --dot
Print a dot for each file read or written (this shows cpio at work without cluttering the screen).
--version
Print version number and then exit.
Examples
Generate a list of files whose names end in .old using find; use list as input to cpio:
find . -name "*. old" -print | cpio -ocBv > /dev/ rst8Restore from a tape drive all files whose names contain save (subdirectories are created if needed):
cpio -icdv "* save*" < /dev/ rst8Move a directory tree:
find . -depth -print | cpio -padm /mydir

cron cron
System administration command. Normally started in a system startup file. Execute commands at scheduled
times, as specified in users' files in /var/ cron/ tabs. Each file shares its name with the user who owns it. The files
are controlled via the command crontab.

crontab crontab [options] [file]
View, install, or uninstall your current crontab file. A privileged user can run crontab for another user by
supplying -u user. A crontab file is a list of commands, one per line, that will execute automatically at a given
time. Numbers are supplied before each command to specify the execution time. The numbers appear in five
fields, as follows:

Minute 0-59 Hour 0-23 Day of month 1-31 Month 1-12 Jan, Feb, Mar, ...

Day of week 0-6, with 0 = Sunday Sun, Mon, Tue, ...

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Use a comma between multiple values, a hyphen to indicate a range, and an asterisk to indicate all possible
values. For example, assuming these crontab entries:

59 3 * * 5 find / -print | backup_ program0 0 1,15 * * echo "Timesheets due" | mail user

The first command backs up the system files every Friday at 3: 59 a. m., and the second command mails a
reminder on the 1st and 15th of each month.

The superuser can always issue the crontab command. Other users must be listed in the file /etc/ cron. allow if it
exists; otherwise, they must not be listed in /etc/ cron. deny. If neither file exists, only the superuser can issue the
command.

Options
The -e, -l, and -r options are not valid if any files are specified.
-e
Edit the user's current crontab file (or create one).
-l
Display the user's crontab file on standard output.
-r
Delete the user's crontab file.
-u user
Indicates which user's crontab file will be acted upon.

csh csh [options] [file [arguments]]
C shell, a command interpreter into which all other commands are entered. For more information, see Chapter 8,
"csh and tcsh".

csplit csplit [options] file arguments
Separate file into context-based sections and place sections in files named xx00 through xxn (n < 100), breaking
file at each pattern specified in arguments. See also split.

Options
-Read
from standard input.
-b suffix, --suffix-format= suffix
Append suffix to output filename. This option causes -n to be ignored. suffix must specify how to convert
the binary integer to readable form by including exactly one of the following: %d, %i, %u, %o, %x, or
%X. The value of suffix determines the format for numbers as follows:

%d
Signed decimal

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%i
Same as %d
%u
Unsigned decimal
%o
Octal
%x
Hexadecimal
%X
Same as %x.
-f prefix, --prefix= prefix
Name new files prefix00 through prefixn (default is xx00 through xxn).
-k, --keep-files
Keep newly created files, even when an error occurs (which would normally remove these files). This is
useful when you need to specify an arbitrarily large repeat argument, {n}, and you don't want an out-of-range
error to cause removal of the new files.

-n num, --digits= num
Use output filenames with numbers num digits long. The default is 2.
-s, -q, --silent, --quiet
Suppress all character counts.
-z, --elide-empty-files
Do not create empty output files. However, number as if those files had been created.
Arguments
Any one or a combination of the following expressions may be specified as arguments. Arguments containing
blanks or other special characters should be surrounded by single quotes.

/expr/[ offset]
Create file from the current line up to the line containing the regular expression expr. offset should be of
the form +n or -n, where n is the number of lines below or above expr.

%expr%[ offset]
Same as /expr/ except no file is created for lines previous to line containing expr.
num
Create file from current line up to (but not including) line number num. When followed by a repeat count
(number inside {}), put the next num lines of input into another output file.

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{n}
Repeat argument n times. May follow any of the preceding arguments. Files will split at instances of expr
or in blocks of num lines. If * is given instead of n, repeat argument until input is exhausted.

Examples
Create up to 20 chapter files from the file novel:
csplit -k -f chap. novel '/ CHAPTER/ ' '{ 20} 'Create up to 100 address files (xx00 through xx99), each four lines long, from a database named address_ list:
csplit -k address_ list 4 {99}

ctags ctags [options] files
Create a list of function and macro names that are defined in the specified C, C++, FORTRAN, Java, Perl, yacc,
or other source files. The output list (named tags by default) contains lines of the form:

name file contextwhere name is the function or macro name, file is the source file in which name is defined, and context is a
search pattern that shows the line of code containing name. After the list of tags is created, you can invoke vi on
any file and type:

:set tags= tagsfile:tag name

This switches the vi editor to the source file associated with the name listed in tagsfile (which you specify with -t).

etags produces an equivalent file for tags to be used with Emacs.
Options
-a, --append
Append tag output to existing list of tags.
-d, --defines
Include tag entries for C preprocessor definitions.
-i file, --include= file
Add a note to the tags file that file should be consulted in addition to the normal input file.
-l language, --language= language
Consider the files that follow this option to be written in language. Use the -h option for a list of
languages and their default filename extensions.

-o file, --output= file
Write to file.
-rregexp, --regex= regexp
Include a tag for each line that matches regexp in the files following this option.

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-R, --no-regex
Don't include tags based on regular-expression matching for the files that follow this option.
-t, --typedefs
Include tag entries for typedefs.
-u, --update
Update tags file to reflect new locations of functions (e. g., when functions are moved to a different source
file). Old tags are deleted; new tags are appended.

-v, --vgrind
Print to standard output a listing (index) of each function, source file, and page number (1 page = 64
lines).

-w, --no-warn
Suppress warning messages.
-x, --cxref
Produce a listing of each function, and its line number, source file, and context.
-B, --backward-search
Search for tags backward through files.
-C, --c++
Expect .c and .h files to contain C++, not C, code.
-H, -h, --help
Print usage information and exit.
-S, --ignore-indentation
Normally ctags uses indentation to parse the tag file; this option tells it to rely on it less.
-T, --typedefs-and-c++
Include tag entries for typedefs, structs, enums, unions, and C++ member functions.
-V, --version
Print the version number and exit.

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cut cut options [files]
Cut out selected columns or fields from one or more files. In the following options, list is a sequence of integers.
Use a comma between separate values and a hyphen to specify a range (e. g., 1-10, 15, 20 or 50-). See also paste
and join.

Options
-b list, --bytes list
Specify list of positions; only bytes in these positions will be printed.
-c list, --characters list
Cut the column positions identified in list.
-d c, --delimiter c
Use with -f to specify field delimiter as character c (default is tab); special characters (e. g., a space) must
be quoted.

-f list, --fields list
Cut the fields identified in list.
-n
Don't split multibyte characters.
-s, --only-delimited
Use with -f to suppress lines without delimiters.
--output-delimiter= string
Use string as the output delimiter. By default, the output delimiter is the same as the input delimiter.
--help
Print help message and then exit.
--version
Print version information and then exit.
Examples
Extract usernames and real names from /etc/ passwd:
cut -d: -f1,5 /etc/ passwdFind out who is logged on, but list only login names:
who | cut -d"" -f1Cut characters in the fourth column of file, and paste them back as the first column in the same file:
cut -c4 file | paste -file

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date date [options] [+ format] [date]
Print the current date and time. You may specify a display format. format can consist of literal text strings
(blanks must be quoted) as well as field descriptors, whose values will appear as described in the following
entries (the listing shows some logical groupings). A privileged user can change the system's date and time.

Options
+format
Display current date in a nonstandard format. For example:
% date +"% A %j %n% k %p"Tuesday 248 15 PM

The default is %a %b %e %T %Z %Y --e. g., Tue Sep 5 14: 59: 37 EDT 2000.
-d date, --date date
Display date, which should be in quotes and may be in the format d days or m months d days to print a
date in the future. Specify ago to print a date in the past. You may include formatting (see the "Format"
section that follows).

-f datefile, --file= datefile
Like -d but printed once for each line of datefile.
-I [timespec], --iso-8601[= timespec]
Display in ISO-8601 format. If specified, timespec can have one of the values date (for date only), hours,
minutes, or seconds to get the indicated precision.

-r file, --reference= file
Display the time file was last modified.
-R, --rfc-822
Display the date in RFC 822 format.
--help
Print help message and exit.
--version
Print version information and exit.
-s date, --set date
Set the date.
-u, --universal
Set the date to Greenwich Mean Time, not local time.
Format
%

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Literal %.

-Do
not pad fields (default: pad fields with zeros).
_
Pad fields with space (default: zeros).
%a
Abbreviated weekday.
%b
Abbreviated month name.
%c
Country-specific date and time format.
%d
Day of month (01-31).
%h
Same as %b.
%j
Julian day of year (001-366).
%k
Hour in 24-hour format, without leading zeros (0-23).
%l
Hour in 12-hour format, without leading zeros (1-12).
%m
Month of year (01-12).
%n
Insert a new line.
%p
String to indicate AM or PM.
%r
Time in %I:% M:% S %p (12-hour) format.
%s

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Seconds since "The Epoch," 1970-01-01 00: 00: 00 UTC (a nonstandard extension).

%t
Insert a tab.
%w
Day of week (Sunday = 0).
%x
Country-specific date format.
%y
Last two digits of year (00-99).
%z
RFC 822-style numeric time zone.
%A
Full weekday.
%B
Full month name.
%D
Date in %m/% d/% y format.
%H
Hour in 24-hour format (00-23).
%I
Hour in 12-hour format (01-12).
%M
Minutes (00-59).
%S
Seconds (00-59).
%T
Time in %H:% M:% S format.
%U
Week number in year (00-53); start week on Sunday.
%V
Week number in year (01-52); start week on Monday.
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%W
Week number in year (00-53); start week on Monday.
%X
Country-specific time format.
%Y
Four-digit year (e. g., 1996).
%Z
Time zone name.
Strings for setting date
Strings for setting the date may be numeric or nonnumeric. Numeric strings consist of time, day, and year in the
format MMDDhhmm[[ CC] YY][. ss]. Nonnumeric strings may include month strings, time zones, a. m., and p. m.

time
A two-digit hour and two-digit minute (hhmm); hh uses 24-hour format.
day
A two-digit month and two-digit day of month (MMDD); default is current day and month.
year
The year specified as either the full four-digit century and year or just the two-digit year; the default is the
current year.

Examples
Set the date to July 1 (0701), 4 a. m. (0400), 1995 (95):
date 0701040095The command:
date +" Hello% t Date is %D %n% t Time is %T"produces a formatted date as follows:

Hello Date is 05/ 09/ 93 Time is 17: 53: 39

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dd dd options
Make a copy of an input file (if) using the specified conditions, and send the results to the output file (or
standard output if of is not specified). Any number of options can be supplied, although if and of are the most
common and are usually specified first. Because dd can handle arbitrary blocksizes, it is useful when converting
between raw physical devices.

Options
bs= n
Set input and output blocksize to n bytes; this option overrides ibs and obs.
cbs= n
Set the size of the conversion buffer (logical record length) to n bytes. Use only if the conversion flag is
ascii, ebcdic, ibm, block, or unblock.

conv= flags
Convert the input according to one or more (comma-separated) flags listed next. The first five flags are
mutually exclusive.

ascii
EBCDIC to ASCII.
ebcdic
ASCII to EBCDIC.
ibm
ASCII to EBCDIC with IBM conventions.
block
Variable-length records (i. e., those terminated by a newline) to fixed-length records.
unblock
Fixed-length records to variable-length.
lcase
Uppercase to lowercase.
ucase
Lowercase to uppercase.
noerror
Continue processing after read errors.
notrunc
Don't truncate output file.
swab

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Swap each pair of input bytes.
sync
Pad input blocks to ibs with trailing zeros.
count= n
Copy only n input blocks.
ibs= n
Set input blocksize to n bytes (default is 512).
if= file
Read input from file (default is standard input).
obs= n
Set output blocksize to n bytes (default is 512).
of= file
Write output to file (default is standard output).
seek= n
Skip n output-sized blocks from start of output file.
skip= n
Skip n input-sized blocks from start of input file.
--help
Print help message and then exit.
--version
Print the version number and then exit.
You can multiply size values (n) by a factor of 1024, 512, or 2 by appending the letter k, b, or w, respectively.
You can use the letter x as a multiplication operator between two numbers.

Examples
Convert an input file to all lowercase:
dd if= caps_ file of= small_ file conv= lcaseRetrieve variable-length data; write it as fixed-length to out:
data_ retrieval_ cmd | dd of= out conv= sync, block

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debugfs debugfs [[ option] device]
System administration command. Debug an ext2 filesystem. device is the special file corresponding to the device
containing the ext2 filesystem (e. g., /dev/ hda3).

Option
-w
Open the filesystem read-write.
Commands
cat file
Dump the contents of an inode to standard output.
cd directory
Change the current working directory to directory.
chroot directory
Change the root directory to be the specified inode.
close
Close the currently open filesystem.
clri file
Clear the contents of the inode corresponding to file.
dump file out_ file
Dump the contents of an inode to out_ file.
expand_ dir directory
Expand directory.
find_ free_ block [goal]
Find first free block starting from goal (if specified) and allocate it.
find_ free_ inode [dir [mode]]
Find a free inode and allocate it.
freeb block
Mark block as not allocated.
freei file
Free the inode corresponding to file.
help
Print a list of commands understood by debugfs.

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icheck block
Do block-to-inode translation.
initialize device blocksize
Create an ext2 filesystem on device.
kill_ file file
Remove file and deallocate its blocks.
ln source_ file dest_ file
Create a link.
ls [pathname]
Emulate the ls command.
modify_ inode file
Modify the contents of the inode corresponding to file.
mkdir directory
Make directory.
mknod file [p|[[ c| b] major minor]]
Create a special device file.
ncheck inode
Do inode-to-name translation.
open [-w] device
Open a filesystem.
pwd
Print the current working directory.
quit
Quit debugfs.
rm file
Remove file.
rmdir directory
Remove directory.
setb block
Mark block as allocated.

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seti file

Mark in use the inode corresponding to file.
show_ super_ stats
List the contents of the super block.
stat file
Dump the contents of the inode corresponding to file.
testb block
Test whether block is marked as allocated.
testi file
Test whether the inode corresponding to file is marked as allocated.
unlink file
Remove a link.
write source_ file file
Create a file in the filesystem named file, and copy the contents of source_ file into the destination file.

depmod depmod [options] modules
System administration command. Create a dependency file for the modules given on the command line. This
dependency file can be used by modprobe to automatically load the relevant modules. The normal use of
depmod is to include the line /sbin/ depmod -a in one of the files in /etc/ rc. d so the correct module dependencies
will be available after booting the system.

Options
-a
Create dependencies for all modules listed in /etc/ conf. modules.
-d
Debug mode. Show all commands being issued.
-e
Print a list of all unresolved symbols.
-v
Print a list of all processed modules.
Files
/etc/ conf. modules
Information about modules: which ones depend on others, and which directories correspond to particular
types of modules.

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/sbin/ insmod, /sbin/ rmmod

Programs that depmod relies on.

df df [options] [name]
Report the amount of free disk space available on all mounted filesystems or on the given name. (df cannot
report on unmounted filesystems.) Disk space is shown in 1KB blocks (default) or 512-byte blocks (if the
environment variable POSIXLY_ CORRECT is set). name can be a device name (e. g., /dev/ hd*), the directory
name of a mounting point (e. g., /usr), or a directory name (in which case df reports on the entire filesystem in
which that directory is mounted).

Options
-a, --all
Include empty filesystems (those with 0 blocks).
--block-size= n
Show space as n-byte blocks.
-h, --human-readable
Print sizes in a format friendly to human readers (e. g., 1.9G instead of 1967156).
-H, --si
Like -h, but show as power of 1000 rather than 1024.
-i, --inodes
Report free, used, and percent-used inodes.
-k, --kilobytes
Print sizes in kilobytes.
-l, --local
Show local filesystems only.
-m, --megabytes
Print sizes in megabytes.
--no-sync
Show results without invoking sync first (i. e., without flushing the buffers). This is the default.
-P, --portability
Use POSIX output format (i. e., print information about each filesystem on exactly one line).
--sync
Invoke sync (flush buffers) before getting and showing sizes.
-t type, --type= type

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Show only type filesystems.

-T, --print-type
Print the type of each filesystem in addition to the sizes.
-x type, --exclude-type= type
Show only filesystems that are not of type type.
--help
Print help message and then exit.
--version
Print the version and then exit.

diff diff [options] [diroptions] file1 file2
Compare two text files. diff reports lines that differ between file1 and file2. Output consists of lines of context
from each file, with file1 text flagged by a < symbol and file2 text by a > symbol. Context lines are preceded by
the ed command (a, c, or d) that would be used to convert file1 to file2. If one of the files is -, standard input is
read. If one of the files is a directory, diff locates the filename in that directory corresponding to the other
argument (e. g., diff my_ dir junk is the same as diff my_ dir/ junk junk). If both arguments are directories, diff
reports lines that differ between all pairs of files having equivalent names (e. g., olddir/ program and
newdir/ program); in addition, diff lists filenames unique to one directory, as well as subdirectories common to
both. See also cmp.

Options
-a, --text
Treat all files as text files. Useful for checking to see if binary files are identical.
-b, --ignore-space-change
Ignore repeating blanks and end-of-line blanks; treat successive blanks as one.
-B, --ignore-blank-lines
Ignore blank lines in files.
-c
Context diff: print 3 lines surrounding each changed line.
-C n, --context[= n]
Context diff: print n lines surrounding each changed line. The default context is 3 lines.
-d, --minimal
To speed up comparison, ignore segments of numerous changes and output a smaller set of changes.
-Dsymbol, --ifdef= symbol
When handling C files, create an output file that contains all the contents of both input files, including
#ifdef and #ifndef directives that reflect the directives in both files.

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-e, --ed

Produce a script of commands (a, c, d) to re-create file2 from file1 using the ed editor.
-F regexp, --show-function-line[= regexp]
For context and unified diff, show the most recent line containing regexp before each block of changed
lines.

-H
Speed output of large files by scanning for scattered small changes; long stretches with many changes
may not show up.

--help
Print brief usage message.
--horizon-lines= n
In an attempt to find a more compact listing, keep n lines on both sides of the changed lines when
performing the comparison.

-i, --ignore-case
Ignore case in text comparison. Uppercase and lowercase are considered the same.
-I regexp, --ignore-matching-lines= regexp
Ignore lines in files that match the regular expression regexp.
-l, --paginate
Paginate output by passing it to pr.
-L label, --label label, --label= label
For context and unified diff, print label in place of the filename being compared. The first such option
applies to the first filename and the second option to the second filename.

--left-column
For two-column output (-y), show only left column of common lines.
-n, --rcs
Produce output in RCS diff format.
-N, --new-file
Treat nonexistent files as empty.
-p, --show-c-function
When handling files in C or C-like languages such as Java, show the function containing each block of
changed lines. Assumes -c but can also be used with a unified diff.

-P, --unidirectional-new-file
If two directories are being compared and the first lacks a file that is in the second, pretend that an empty
file of that name exists in the first directory.

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-q, --brief
Output only whether files differ.
-r, --recursive
Compare subdirectories recursively.
-s, --report-identical-files
Indicate when files do not differ.
-S filename, --starting-file= filename
For directory comparisons, begin with the file filename, skipping files that come earlier in the standard
list order.

--suppress-common-lines
For two-column output (-y), do not show common lines.
-t, --expand-tabs
Produce output with tabs expanded to spaces.
-T, --initial-tab
Insert initial tabs into output to line up tabs properly.
-u
Unified diff: print old and new versions of lines in a single block, with 3 lines surrounding each block of
changed lines.

-U n, --unified[= n]
Unified diff: print old and new versions of lines in a single block, with n lines surrounding each block of
changed lines. The default context is 3 lines.

-v, --version
Print version number of this version of diff.
-w, --ignore-all-space
Ignore all whitespace in files for comparisons.
-W n, --width= n
For two-column output (-y), produce columns with a maximum width of n characters. Default is 130.
-x regexp, --exclude= regexp
Do not compare files in a directory whose names match regexp.
-X filename, --exclude-from= filename
Do not compare files in a directory whose names match patterns described in the file filename.
-y, --side-by-side

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Produce two-column output.
-n
For context and unified diff, print n lines of context. Same as specifying a number with -C or -U.

diff3 diff3 [options] file1 file2 file3
Compare 3 files and report the differences. No more than one of the files may be given as -(indicating that it is
to be read from standard input). The output is displayed with the following codes:

====
All three files differ.
==== 1
file1 is different.
==== 2
file2 is different.
==== 3
file3 is different.
diff3 is also designed to merge changes in two differing files based on a common ancestor file (i. e., when two
people have made their own set of changes to the same file). diff3 can find changes between the ancestor and
one of the newer files and generate output that adds those differences to the other new file. Unmerged changes
are places where both of the newer files differ from each other and at least one of them from the ancestor.
Changes from the ancestor that are the same in both of the newer files are called merged changes. If all three
files differ in the same place, it is called an overlapping change.

This scheme is used on the command line with the ancestor being file2, the second filename. Comparison is
made between file2 and file3, with those differences then applied to file1.

Options
-3, --easy-only
Create an ed script to incorporate into file1 unmerged, nonoverlapping differences between file1 and
file3.

-a, --text
Treat files as text.
-A, --show-all
Create an ed script to incorporate all changes, showing conflicts in bracketed format.
-e, --ed
Create an ed script to incorporate into file1 all unmerged differences between file2 and file3.
-E, --show-overlap
Create an ed script to incorporate unmerged changes, showing conflicts in bracketed format.

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-x, --overlap-only

Create an ed script to incorporate into file1 all differences where all three files differ (overlapping
changes).

-X
Same as -x, but show only overlapping changes, in bracketed format.
-m, --merge
Create file with changes merged (not an ed script).
-L label, --label= label
Use label to replace filename in output.
-i
Append the w (save) and q (quit) commands to ed script output.
-T, --initial-tab
Begin lines with a tab instead of two spaces in output to line tabs up properly.
-v, --version
Print version information and then exit.

dip dip [options] [chat scriptfile]
System administration command. Set up or initiate dial-up Internet connections. dip can be used to establish
connections for users dialing out or dialing in. Commands can be used in interactive mode or placed in a script
file for use in dial-out connections. To establish dial-in connections, dip is often is used as a shell and may be
executed using the commands diplogin or diplogini.

Options
-a
In dial-in mode, prompt for username and password. Same as the diplogini command.
-i
Initiate a login shell for a dial-in connection. Same as the diplogin command.
-k
Kill the most recent dip process or the process running on the device specified by the -l option.
-l device
Used with the -k option. Specifies a tty device.
-m mtu
Maximum Transfer Unit. The default is 296.
-p protocol

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The protocol to use: SLIP, CSLIP, PPP, or TERM.

-t
Command mode. This is usually done for testing.
-v
Verbose mode.
Commands
Most of these commands can be used either in interactive mode or in a script file.
beep times
Beep the terminal the specified number of times.
bootp
Retrieve local and remote IP addresses using the BOOTP protocol.
break
Send a BREAK.
chatkey keyword code
Map a modem response keyword to a numeric code.
config [interface| routing] [pre| up| down| post] arguments
Modify interface characteristics or the routing table, before the link comes up, when it is up, when it
goes down, or after it is down. The syntax for arguments is the same as arguments for the ifconfig or
route commands.

databits 7| 8
Set the number of data bits.
dec $variable [value]
Decrement $variable by value. The default is 1.
default
Set default route to the IP address of the host connected to.
dial phonenumber [timeout]
Dial phonenumber. Abort if remote modem doesn't answer within timeout seconds. Set $errlvl according
to the modem response.

echo on| off
Enable or disable the display of modem commands.
exit [n]
Exit the script. Optionally return the number n as the exit status.

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flush

Clear the input buffer.
get $variable [ask| remote [timeout]] value
Set $variable to value. If ask is specified, prompt the user for a value. If remote is specified, retrieve the
value from the remote system. Abort after timeout seconds.

goto label
Jump to the section identified by label.
help
List available commands.
if expr goto label
Jump to the section identified by label if the expression evaluates to true. An expression compares a
variable to a constant using one of these operators: =, !=, <, >, <=, or >=.

inc $variable [value]
Increment $variable by value. The default is 1.
init string
Set the string used to initialize the modem. The default is ATE0 Q0 V1 X1.
mode protocol
Set the connection protocol. Valid values are SLIP, CSLIP, PPP, and TERM. The default is SLIP.
netmask mask
Set the subnet mask.
parity E| O| N
Set the line parity to even, odd, or none.
password
Prompt user for password.
proxyarp
Install a proxy ARP entry in the local ARP table.
print $variable
Display the content of $variable.
psend command
Execute command in a shell, and send output to the serial device. Commands are executed using the
user's real UID.

port device

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Specify the serial device the modem is attached to.

quit
Exit with a nonzero exit status. Abort the connection.
reset
Reset the modem.
securid
Prompt user for the variable part of an ACE System SecureID password and send it together with the
stored prefix to the remote system.

securidf prefix
Store the fixed part of an ACE System SecureID password.
send string
Send string to the serial device.
shell command
Execute command in a shell using the user's real UID.
skey [timeout]
Wait for an S/ Key challenge, then prompt user for the secret key. Generate and send the response. Abort
if challenge is not received within timeout seconds. S/ Key support must be compiled into dip.

sleep time
Wait time seconds.
speed bits-per-second
Set the port speed. Default is 38400.
stopbits 1| 2
Set the number of stop bits.
term
Enable terminal mode. Pass keyboard input directly to the serial device.
timeout time
Set the number of seconds the line can be inactive before the link is closed.
wait text [timeout]
Wait timeout seconds for text to arrive from the remote system. If timeout is not specified, wait forever.

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dirname dirname pathname
Print pathname excluding the last level. Useful for stripping the actual filename from a pathname. If there are no
slashes (no directory levels) in pathname, dirname prints . to indicate the current directory. See also basename.

dmesg dmesg [options]
System administration command. Display the system control messages from the kernel ring buffer. This buffer
stores all messages since the last system boot or the most recent ones, if the buffer has been filled.

Options
-c
Clear buffer after printing messages.
-n level
Set the level of system message that will display on console.

dnsdomainname dnsdomainname
TCP/ IP command. Print the system's DNS domain name. See also hostname.

domainname domainname [name]
NFS/ NIS command. Set or display name of current NIS domain. With no argument, domainname displays the
name of the current NIS domain. Only a privileged user can set the domain name by giving an argument; this is
usually done in a startup script.

dosfsck dosfsck [options] device
fsck. ext2 [options] device
System administration command. Similar to fsck, but specifically intended for MS-DOS filesystems. When
checking an MS-DOS filesystem, fsck calls this command. Normally dosfsck stores all changes in memory, then
writes them when checks are complete.

Options
-a
Automatically repair the system; do not prompt the user.
-A
Use the Atari version of the MS-DOS filesystem.
-d file
Drop the named file from the file allocation table. Force checking, even if kernel has already marked the
filesystem as valid. dosfsck will normally exit without checking if the system appears to be clean.

-l file
Consult file for a list of bad blocks, in addition to checking for others.

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-n

Ensure that no changes are made to the filesystem. When queried, answer "no."
-p
"Preen." Repair all bad blocks noninteractively.
-t
Display timing statistics.
-v
Verbose.
-y
When queried, answer "yes."
-B size
Expect to find the superblock at size; if it's not there, exit.
-F
Flush buffer caches before checking.
-L file
Consult file for list of bad blocks instead of checking filesystem for them.

du du [options] [directories]
Print disk usage (as the number of 1KB blocks used by each named directory and its subdirectories; default is
current directory).

Options
-a, --all
Print usage for all files, not just subdirectories.
-b, --bytes
Print sizes in bytes.
-c, --total
In addition to normal output, print grand total of all arguments.
-D, --dereference-args
Follow symbolic links, but only if they are command-line arguments.
-h, --human-readable
Print sizes in human-reader-friendly format.
-H, --si

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Like -h, but show as power of 1000 rather than 1024.
-k, --kilobytes
Print sizes in kilobytes (this is the default).
-l, --count-links
Count the size of all files, whether or not they have already appeared (i. e., via a hard link).
-L, --dereference
Follow symbolic links.
--exclude= pattern
Exclude files that match pattern.
--max-depth= num
Report sizes for directories only down to num levels below the starting point (which is level 0).
-m, --megabytes
Print sizes in megabytes.
-s, --summarize
Print only the grand total for each named directory.
-S, --separate-dirs
Do not include the sizes of subdirectories when totaling the size of parent directories.
-x, --one-file-system
Display usage of files in current filesystem only.
-X, --exclude-from= file
Exclude files that match any pattern in file.
--help
Print help message and then exit.
--version
Print the version and then exit.

dumpe2fs dumpe2fs device
System administration command. Print information about device's superblock and blocks group.

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dumpkeys dumpkeys [options]
Print information about the keyboard driver's translation tables to standard output. Further information is
available in the manual pages under keytables.

Options
-1, --separate-lines
Print one line for each modifier/ keycode pair and prefix plain to each unmodified keycode.
-ccharset, --charset= charset
Specify character set with which to interpret character code values. The default character set is iso-8859-
1. The full list of valid character sets is available with the --help option.

--compose-only
Print compose key combinations only. Requires compose key support in the kernel.
-f, --full-table
Output in canonical, not short, form: for each key, print a row with modifier combinations divided into
columns.

--funcs-only
Print function key string definitions only; do not print key bindings or string definitions.
-h, --help
Print help message and the version.
-i, --short-info
Print in short-info format, including information about acceptable keycode keywords in the keytable files;
the number of actions that can be bound to a key; a list of the ranges of action codes (the values to the
right of a key definition); and the number of function keys that the kernel supports.

--keys-only
Print key bindings only; do not print string definitions.
-l, --long-info
Print the same information as in --short-info, plus a list of the supported action symbols and their
numeric values.

-n, --numeric
Print action code values in hexadecimal notation; do not attempt to convert them to symbolic notation.
-S num, --shape= num
Print using num to determine table shape. Values of num are:
0
Default

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1

Same as --full-table
2
Same as --separate-lines
3
One line for each keycode up to the first hole, then one line per modifier/ keycode pair

e2fsck e2fsck [options] device
fsck. ext2 [options] device
System administration command. Similar to fsck, but specifically intended for Linux Second Extended
Filesystems. When checking a second extended filesystem, fsck calls this command.

Options
-b superblock
Use superblock instead of default superblock.
-d
Debugging mode.
-f
Force checking, even if kernel has already marked the filesystem as valid. e2fsck will normally exit
without checking if the system appears to be clean.

-l file
Consult file for a list of bad blocks, in addition to checking for others.
-n
Ensure that no changes are made to the filesystem. When queried, answer "no."
-p
"Preen." Repair all bad blocks noninteractively.
-t
Display timing statistics.
-v
Verbose.
-y
When queried, answer "yes."
-B size

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Expect to find the superblock at size; if it's not there, exit.

-F
Flush buffer caches before checking.
-L file
Consult file for list of bad blocks instead of checking filesystem for them.

echo echo [-n] [string]
This is the /bin/ echo command. echo also exists as a command built into the C shell and bash. The following
character sequences have special meanings:

\a
Alert (bell)
\b
Backspace
\c
Suppress trailing newline
\f
Form feed
\n
Newline
\r
Carriage return
\t
Horizontal tab
\v
Vertical tab
\\
Literal backslash
\nnn
The octal character whose ASCII code is nnn.
Options
-e
Enable character sequences with special meaning. (In some versions, this option is not required in order

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to make the sequences work.)

-E
Disable character sequences with special meaning.
-n
Suppress printing of newline after text.
--help
Print help message and then exit.
--version
Print version information and then exit.
Examples
/bin/ echo "testing printer" | lp /bin/ echo "TITLE\ nTITLE" > file ; cat doc1 doc2 >> file /bin/ echo "Warning: ringing bell \a"

egrep egrep [options] [regexp] [files]
Search one or more files for lines that match an extended regular expression regexp. egrep doesn't support the
regular expressions $, $, \n, \<, \>, \{, or \} but does support the other expressions, as well as the extended set +,
?, |, and ( ). Remember to enclose these characters in quotes. Regular expressions are described in Chapter 9,

"Pattern Matching". Exit status is 0 if any lines match, 1 if none match, and 2 for errors.

See grep for the list of available options. Also see fgrep. egrep typically runs faster than those commands.
Examples
Search for occurrences of Victor or Victoria in file:
egrep 'Victor( ia)* ' fileegrep '( Victor| Victoria) ' file

Find and print strings such as old. doc1 or new. doc2 in files, and include their line numbers:
egrep -n '( old| new)\. doc? ' files

emacs emacs [options] [files]
A text editor and all-purpose work environment. For more information, see Chapter 10, "The Emacs Editor".

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env env [option] [variable= value ... ] [command]
Display the current environment or, if an environment variable is specified, set it to a new value and display the
modified environment. If command is specified, execute it under the modified environment.

Options
-, -i, --ignore-environment
Ignore current environment entirely.
-u name, --unset name
Unset the specified variable.
--help
Print help message and then exit.
--version
Print version information and then exit.

etags etags [options] files
Create a list of function and macro names that are defined in the specified C, Pascal, FORTRAN, yacc, or flex
source files. The output list (named tags by default) contains lines of the form:

ESC-x visit-tags-tableYou will be prompted for the name of the tag table; the default is TAGS. To switch to the source file associated
with the name listed in tagsfile, type:

ESC-x find-tagYou will be prompted for the tag you would like Emacs to search for. ctags produces an equivalent tags file for
use with vi.

Options
-a, --append
Append tag output to existing list of tags.
-d, --defines
Include tag entries for C preprocessor definitions.
-i file, --include= file
Add a note to the tags file that file should be consulted in addition to the normal input file.
-l language, --language= language

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Consider the files that follow this option to be written in language. Use the -h option for a list of
languages and their default filename extensions.

-o file, --output= file
Write to file.
-r regexp, --regex= regexp
Include a tag for each line that matches regexp in the files following this option.
-C, --c++
Expect .c and .h files to contain C++, not C, code.
-D, --no-defines
Do not include tag entries for C preprocessor definitions.
-H, -h, --help
Print usage information.
-R, --noregex
Don't include tags based on regular-expression matching for the files that follow this option.
-S, --ignore-indentation
Normally etags uses indentation to parse the tag file; this option tells it to rely on it less.
-V, --version
Print the version number.

ex ex [options] file
An interactive command-based editor. For more information, see Chapter 11, "The vi Editor".

expand expand [options] files
Convert tabs in given files (or standard input, if the file is named -) to appropriate number of spaces; write
results to standard output.

Options
-tabs, -t, --tabs tabs
tabs is a comma-separated list of integers that specify the placement of tab stops. If exactly one integer is
provided, the tab stops are set to every integer spaces. By default, tab stops are 8 spaces apart. With -t
and --tabs, the list may be separated by whitespace instead of commas.

-i, --initial
Convert tabs only at the beginning of lines.
--help
Print help message and then exit.

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--version
Print version information and then exit.

expr expr arg1 operator arg2 [ operator arg3 ... ]
Evaluate arguments as expressions and print the result. Arguments and operators must be separated by spaces. In
most cases, an argument is an integer, typed literally or represented by a shell variable. There are three types of
operators: arithmetic, relational, and logical, as well as keyword expressions. Exit status for expr is 0
(expression is nonzero and nonnull), 1 (expression is 0 or null), or 2 (expression is invalid).

Arithmetic operators
Use these to produce mathematical expressions whose results are printed:
+
Add arg2 to arg1.
-Subtract
arg2 from arg1.
*
Multiply the arguments.
/
Divide arg1 by arg2.
%
Take the remainder when arg1 is divided by arg2.
Addition and subtraction are evaluated last, unless they are grouped inside parentheses. The symbols *, (, and )
have meaning to the shell, so they must be escaped (preceded by a backslash or enclosed in single quotes).

Relational operators
Use these to compare two arguments. Arguments can also be words, in which case comparisons are defined by
the locale. If the comparison statement is true, the result is 1; if false, the result is 0. Symbols > and < must be
escaped.

=, ==
Are the arguments equal?
!=
Are the arguments different?
>
Is arg1 greater than arg2?
>=
Is arg1 greater than or equal to arg2?

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<

Is arg1 less than arg2?
<=
Is arg1 less than or equal to arg2?
Logical operators
Use these to compare two arguments. Depending on the values, the result can be arg1 (or some portion of it),
arg2, or 0. Symbols | and & must be escaped.

|
Logical OR; if arg1 has a nonzero (and nonnull) value, the result is arg1; otherwise, the result is arg2.
&
Logical AND; if both arg1 and arg2 have a nonzero (and nonnull) value, the result is arg1; otherwise, the
result is 0.

:Like grep; arg2 is a pattern to search for in arg1. arg2 must be a regular expression. If part of the arg2
pattern is enclosed in , the result is the portion of arg1 that matches; otherwise, the result is simply the
number of characters that match. By default, a pattern match always applies to the beginning of the first
argument (the search string implicitly begins with a ^). Start the search string with .* to match other parts
of the string.

Keywords
index string character-list
Return the first position in string that matches the first possible character in character-list. Continue
through character-list until a match is found, or return 0.

length string
Return the length of string.
match string regex
Same as string : regex.
quote token
Treat token as a string, even if it would normally be a keyword or an operator.
substr string start length
Return a section of string, beginning with start, with a maximum length of length characters. Return null
when given a negative or nonnumeric start or length.

Examples
Division happens first; result is 10:
expr 5 + 10 / 2Addition happens first; result is 7 (truncated from 7.5):

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expr $ 5 + 10 $ / 2Add 1 to variable i. This is how variables are incremented in shell scripts:
i= `expr $i + 1Print 1 (true) if variable a is the string "hello":
expr $a = helloPrint 1 (true) if b plus 5 equals 10 or more:
expr $b + 5 \>= 10Find the 5th, 6th, and 7th letters of the word character:
expr substr character 5 3In the examples that follow, variable p is the string "version. 100". This command prints the number of characters
in p:

expr $p : '.* ' Result is 11Match all characters and print them:
expr $p : '$.*$ ' Result is "version. 100"Print the number of lowercase letters at the beginning of p:
expr $p : '[ a-z]* ' Result is 7Match the lowercase letters at the beginning of p:
expr $p : '$[ a-z]*$ ' Result is "version"Truncate $x if it contains five or more characters; if not, just print $x. (Logical OR uses the second argument
when the first one is 0 or null; i. e., when the match fails.)

expr $x : '$.....$ ' \| $xIn a shell script, rename files to their first five letters:
mv $x `expr $x : '$.....$ ' \| $x(To avoid overwriting files with similar names, use mv -i.)

false false
A null command that returns an unsuccessful (nonzero) exit status. Normally used in bash scripts. See also true.

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fdformat fdformat [options] device
Low-level format of a floppy disk. The device for a standard format is usually /dev/ fd0 or /dev/ fd1.
Option
-n
Do not verify format after completion.

fdisk fdisk [options] [device]
System administration command. Maintain disk partitions via a menu. fdisk displays information about disk
partitions, creates and deletes disk partitions, and changes the active partition. It is possible to assign a different
operating system to each of the four partitions, though only one partition is active at any given time. You can
also divide a physical partition into several logical partitions. The minimum recommended size for a Linux
system partition is 40MB. Normally, device will be /dev/ hda, /dev/ hdb, /dev/ sda, /dev/ sdb, /dev/ hdc, /dev/ hdd,
and so on. See also cfdisk.

Options
-l
List partition tables and exit.
-spartition
Display the size of partition, unless it is a DOS partition.
Commands
a
Toggle a bootable flag on current partition.
d
Delete current partition.
l
List all partition types.
m
Main menu.
n
Create a new partition; prompt for more information.
p
Print a list of all partitions and information about each.
q
Quit; do not save.
t
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Replace the type of the current partition.
u
Modify the display/ entry units, which must be cylinders or sectors.
v
Verify: check for errors; display a summary of the number of unallocated sectors.
w
Save changes; exit.

fetchmail fetchmail [options] [servers...]
System administration command. Retrieve mail from mail servers and forward it to the local mail delivery
system. fetchmail retrieves mail from servers that support the common mail protocols POP2, POP3, IMAP2bis,
and IMAP4. Messages are delivered via SMTP through port 25 on the local host and through your system's mail
delivery agent (such as sendmail), where they can be read through the user's mail client. fetchmail settings are
stored in the ~/. fetchmailrc file. Parameters and servers can also be set on the command line, which will override
settings in the .fetchmailrc file. fetchmail is compatible with the popclient program, and users can use both
without having to adjust file settings.

Options
-a, --all
Retrieve all messages from server, even ones that have already been seen but left on the server. The
default is to only retrieve new messages.

-A type, --auth type
Specify the type of authentication. type may be: password, kerberos_ v5, or kerberos. Authentication
type is usually established by fetchmail by default, so this option isn't very useful.

-B n, --fetchlimit n
Set the maximum number of messages (n) accepted from a server per query.
-b n, --batchlimit n
Set the maximum number of messages sent to an SMTP listener per connection. When this limit is
reached, the connection will be broken and reestablished. The default of 0 means no limit.

-c, --check
Check for mail on a single server without retrieving or deleting messages. Works with IMAP but not well
with other protocols, if at all.

-D [domain], --smtpaddress [domain]
Specify the domain name placed in RCPT TO lines sent to SMTP. The default is the local host.
-E header, --envelope header
Change the header assumed to contain the mail's envelope address (usually "X-Envelope-to:") to header.
-e n, --expunge n

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Tell an IMAP server to EXPUNGE (i. e., purge messages marked for deletion) after n deletes. A setting of
0 indicates expunging only at the end of the session. Normally, an expunge occurs after each delete.

-F, --flush
For POP3 and IMAP servers, remove previously retrieved messages from the server before retrieving
new ones.

-f file, --fetchmailrc file
Specify a nondefault name for the fetchmail configuration file.
-I specification, --interface specification
Require that the mail server machine is up and running at a specified IP address (or range) before polling.
The specification is given as interface/ ipaddress/ mask. The first part indicates the type of TCP
connection expected (sl0, ppp0, etc.), the second is the IP address, and the third is the bit mask for the IP,
assumed to be 255.255.255.255.

-K, --nokeep
Delete all retrieved messages from the mail server.
-k, --keep
Keep copies of all retrieved messages on the mail server.
-l size, --limit size
Set the maximum message size that will be retrieved from a server. Messages larger than this size will be
left on the server and marked unread.

-M interface, --monitor interface
In daemon mode, monitor the specified TCP/ IP interface for any activity besides itself, and skip the poll
if there is no other activity. Useful for PPP connections that automatically time out with no activity.

-m command, --mda command
Pass mail directly to mail delivery agent, rather than send to port 25. The command is the path and
options for the mailer, such as /usr/ lib/ sendmail -oem. A %T in the command will be replaced with the
local delivery address, and an %F will be replaced with the message's From address.

-n, --norewrite
Do not expand local mail IDs to full addresses. This option will disable expected addressing and should
only be used to find problems.

-P n, --port n
Specify a port to connect to on the mail server. The default port numbers for supported protocols are
usually sufficient.

-p proto, --protocol proto
Specify the protocol to use when polling a mail server. proto can be:
POP2
Post Office Protocol 2.

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POP3

Post Office Protocol 3.
APOP
POP3 with MD5 authentication.
RPOP
POP3 with RPOP authentication.
KPOP
POP3 with Kerberos v4 authentication on port 1109.
IMAP
IMAP2bis, IMAP4, or IMAP4rev1. fetchmail autodetects their capabilities.
IMAP-K4
IMAP4 or IMAP4rev1 with Kerberos v4 authentication.
IMAP-GSS
IMAP4 or IMAP4rev1 with GSSAPI authentication.
ETRN
ESMTP.
-Q string, --qvirtual string
Remove the prefix string, which is the local user's hostid, from the address in the envelope header (such
as "Delivered-To:").

-r folder, --folder folder
Retrieve the specified mail folder from the mail server.
-s, --silent
Suppress status messages during a fetch.
-U, --uidl
For POP3, track the age of kept messages via unique ID listing.
-u name, --username name
Specify the user name to use when logging into the mail server.
-V, --version
Print the version information for fetchmail and display the options set for each mail server. Performs no
fetch.

-v, --verbose
Display all status messages during a fetch.

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-Z nnn, --antispam nnn
Specify the SMTP error nnn to signal a spam block from the client. If nnn is -1, this option is disabled.

fgrep fgrep [options] pattern [files]
Search one or more files for lines that match a literal text string pattern. Exit status is 0 if any lines match, 1 if
not, and 2 for errors.

See grep for the list of available options. Also see egrep.
Examples
Print lines in file that don't contain any spaces:
fgrep -v '' filePrint lines in file that contain the words in spell_ list:
fgrep -f spell_ list file

file file [options] files
Classify the named files according to the type of data they contain. file checks the magic file (usually
/usr/ share/ magic) to identify some file types.

Options
-b
Brief mode; do not prepend filenames to output lines.
-c
Check the format of the magic file (files argument is invalid with -c). Usually used with -m.
-f file
Read the names of files to be checked from file.
-L
Follow symbolic links. By default, symbolic links are not followed.
-m file
Search for file types in file instead of /usr/ share/ magic.
-n
Flush standard output after checking a file.
-s
Check files that are block or character special files in addition to checking ordinary files.
-v

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Print the version.

-z
Attempt checking of compressed files.
Many file types are understood. Output lists each filename, followed by a brief classification such as:
ascii text c program text c-shell commands data empty iAPX 386 executable directory [nt] roff, tbl, or eqn input text shell commands symbolic link to ../ usr/ etc/ arp

Example
List all files that are deemed to be troff/ nroff input:
file * | grep roff

find find [pathnames] [conditions]
An extremely useful command for finding particular groups of files (numerous examples follow this
description). find descends the directory tree beginning at each pathname and locates files that meet the
specified conditions. The default pathname is the current directory. The most useful conditions include -print
(which is the default if no other expression is given), -name and -type (for general use), -exec and -size (for
advanced users), and -mtime and -user (for administrators).

Conditions may be grouped by enclosing them in  (escaped parentheses), negated with ! (use \! in the C
shell), given as alternatives by separating them with -o, or repeated (adding restrictions to the match; usually
only for -name, -type, -perm). Modification refers to editing of a file's contents. Change refers to modification,
permission or ownership changes, and so on; therefore, for example, -ctime is more inclusive than -atime or -mtime.

Conditions and actions
-atime +n | -n | n
Find files that were last accessed more than n (+ n), less than n (-n), or exactly n days ago. Note that find
changes the access time of directories supplied as pathnames.

-ctime +n | -n | n
Find files that were changed more than n (+ n), less than n (-n), or exactly n days ago. A change is
anything that changes the directory entry for the file, such as a chmod.

-depth
Descend the directory tree, skipping directories and working on actual files first (and then the parent
directories). Useful when files reside in unwritable directories (e. g., when using find with cpio).

-exec command { } \;
Run the Linux command, from the starting directory on each file matched by find (provided command
executes successfully on that file; i. e., returns a 0 exit status). When command runs, the argument { }
substitutes the current file. Follow the entire sequence with an escaped semicolon (\;).

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-follow
Follow symbolic links and track the directories visited (don't use this with -type l).
-group gname
Find files belonging to group gname. gname can be a group name or a group ID number.
-inum n
Find files whose inode number is n.
-links n
Find files having n links.
-mount, -xdev
Search for files that reside only on the same filesystem as pathname.
-mtime +n | -n | n
Find files that were last modified more than n (+ n), less than n (-n), or exactly n days ago. A modification
is a change to a file's data.

-name pattern
Find files whose names match pattern. Filename metacharacters may be used but should be escaped or
quoted.

-newer file
Find files that have been modified more recently than file; similar to -mtime. Affected by -follow only if
it occurs after -follow on the command line.

-ok command { }\;
Same as -exec but prompts user to respond with y before command is executed.
-perm nnn
Find files whose permission flags (e. g., rwx) match octal number nnn exactly (e. g., 664 matches -rw-rw-r--).
Use a minus sign before nnn to make a "wildcard" match of any unspecified octal digit (e. g., -perm -600
matches -rw-******, where * can be any mode).

-print
Print the matching files and directories, using their full pathnames. Return true.
-regex pattern
Like -path but uses grep-style regular expressions instead of the shell-like globbing used in -name and -path.

-size n[ c]
Find files containing n blocks, or if c is specified, n characters long.
-type c

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Find files whose type is c. c can be b (block special file), c (character special file), d (directory), p (fifo
or named pipe), l (symbolic link), s (socket), or f (plain file).

-user user
Find files belonging to user (name or ID).
-daystart
Calculate times from the start of the day today, not 24 hours ago.
-maxdepth num
Do not descend more than num levels of directories.
-mindepth num
Begin applying tests and actions only at levels deeper than num levels.
-noleaf
Normally, find assumes that each directory has at least two hard links that should be ignored (a hard link
for its name and one for "."; i. e., two fewer "real" directories than its hard link count indicates). -noleaf
turns off this assumption, a useful practice when find runs on non-Unix-style filesystems. This forces
find to examine all entries, assuming that some might prove to be directories into which it must descend
(a time-waster on Unix).

-amin +n | -n | n
Find files last accessed more than n (+ n), less than n (-n), or exactly n minutes ago.
-anewer file
Find files that were accessed after file was last modified. Affected by -follow when after -follow on the
command line.

-cmin +n | -n | n
Find files last changed more than n (+ n), less than n (-n), or exactly n minutes ago.
-cnewer file
Find files that were changed after they were last modified. Affected by -follow when after -follow on the
command line.

-empty
Continue if file is empty. Applies to regular files and directories.
-false
Return false value for each file encountered.
-fstype type
Match files only on type filesystems. Acceptable types include minix, ext, ext2, xia, msdos, umsdos,
vfat, proc, nfs, iso9660, hpfs, sysv, smb, and ncpfs.

-gid num
Find files with numeric group ID of num.

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-ilname pattern
A case-insensitive version of -lname.
-iname pattern
A case-insensitive version of -name.
-ipath pattern
A case-insensitive version of -path.
-iregex pattern
A case-insensitive version of -regex.
-lname pattern
Search for files that are symbolic links, pointing to files named pattern. pattern can include shell
metacharacters and does not treat / or . specially. The match is case-insensitive.

-mmin +n | -n | n
Find files last modified more than n (+ n), less than n (-n), or exactly n minutes ago.
-nouser
The file's user ID does not correspond to any user.
-nogroup
The file's group ID does not correspond to any group.
-path pattern
Find files whose names match pattern. Expect full pathnames relative to the starting pathname (i. e., do
not treat / or . specially).

Examples
List all files (and subdirectories) in your home directory:
find $HOME -printList all files named chapter1 in the /work directory:
find /work -name chapter1 -printList all files beginning with memo owned by ann:
find /work -name 'memo* ' -user ann -printSearch the filesystem (begin at root) for manpage directories:
find / -type d -name 'man* ' -printSearch the current directory, look for filenames that don't begin with a capital letter, and send them to the
printer:

find . \! -name '[ A-Z]* ' -exec lpr {}\;

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Find and compress files whose names don't end with .gz:
gzip `find . \! -name '*. gz' -printRemove all empty files on the system (prompting first):
find / -size 0 -ok rm {} \;Search the system for files that were modified within the last two days (good candidates for backing up):
find / -mtime -2 -printRecursively grep for a pattern down a directory tree:
find /book -print | xargs grep '[ Nn] utshell'If the files kt1 and kt2 exist in the current directory, their names can be printed with the command:
$ find . -name 'kt[ 0-9] './ kt1 ./ kt2

Since the command prints these names with an initial ./ path, you need to specify the ./ when using the -path
option:

$ find . -path './ kt[ 0-9] './ kt1 ./ kt2

The -regex option uses a complete pathname, like -path, but treats the following argument as a regular
expression rather than a glob pattern (although in this case the result is the same):

$ find . -regex './ kt[ 0-9] './ kt1 ./ kt2

finger finger [options] users
Display data about one or more users, including information listed in the files .plan and .project in each user's
home directory. You can specify each user either as a login name (exact match) or as a first or last name (display
information on all matching names). Networked environments recognize arguments of the form user@ host and
@host.

Options
-l
Force long format (default): everything included by the -s option and home directory, home phone, login
shell, mail status, .plan, .project, and .forward.

-m
Suppress matching of users' "real" names.
-p
Omit .plan and .project files from display.
-s

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Show short format: login name, real name, terminal name, write status, idle time, office location, and
office phone number.

fingerd in. fingerd [option]
TCP/ IP command. Remote user information server. fingerd provides a network interface to the finger program.
It listens for TCP connections on the finger port and, for each connection, reads a single input line, passes the
line to finger, and copies the output of finger to the user on the client machine. fingerd is started by inetd and
must have an entry in inetd's configuration file, /etc/ inetd. conf.

Option
-w
Include additional information, such as uptime and the name of the operating system.

flex flex [options] [file]
flex (Fast Lexical Analyzer Generator) is a faster variant of lex. It generates a lexical analysis program (named
lex. yy. c) based on the regular expressions and C statements contained in one or more input files. See also bison,
yacc, and the O'Reilly book lex & yacc by John Levine, Tony Mason, and Doug Brown.

Options
-b
Generate backup information to lex. backup.
-d
Debug mode.
-f
Use faster compilation (limited to small programs).
-h
Help summary.
-i
Scan case-insensitively.
-l
Maximum lex compatibility.
-o file
Write output to file instead of lex. yy. c.
-p
Print performance report.
-s
Exit if the scanner encounters input that does not match any of its rules.

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-t
Print to standard out. (By default, flex prints to lex. yy. c.)
-v
Print a summary of statistics.
-w
Suppress warning messages.
-B
Generate batch (noninteractive) scanner.
-F
Use the fast scanner table representation.
-I
Generate an interactive scanner (default).
-L
Suppress #line directives in lex. yy. c.
-P prefix
Change default yy prefix to prefix for all globally visible variable and function names.
-V
Print version number.
-7
Generate a 7-bit scanner.
-8
Generate an 8-bit scanner (default).
-+
Generate a C++ scanner class.
-C
Compress scanner tables but do not use equivalence classes.
-Ca
Align tables for memory access and computation. This creates larger tables but gives faster performance.
-Ce
Construct equivalence classes. This creates smaller tables and sacrifices little performance (default).

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-Cf

Generate full scanner tables, not compressed.
-CF
Generate faster scanner tables, like -F.
-Cm
Construct metaequivalence classes (default).
-Cr
Bypass use of the standard I/ O library. Instead use read() system calls.

fmt fmt [options] [files]
Convert text to specified width by filling lines and removing newlines. Concatenate files on the command line,
or read text from standard input if -(or no file) is specified. By default, preserve blank lines, spacing, and
indentation. fmt attempts to break lines at the end of sentences and to avoid breaking lines after a sentence's first
word or before its last.

Options
-c, --crown-margin
Crown margin mode. Do not change each paragraph's first two lines' indentation. Use the second line's
indentation as the default for subsequent lines.

-p prefix, --prefix= prefix
Format only lines beginning with prefix.
-s, --split-only
Suppress line-joining.
-t, --tagged-paragraph
Tagged paragraph mode. Same as crown mode when the indentation of the first and second lines differs.
If the indentation is the same, treat the first line as its own separate paragraph.

-u, --uniform-spacing
Print exactly one space between words and two between sentences.
-w width, --width= width
Set output width to width. The default is 75.
--help
Print help message and then exit.
--version
Print version information and then exit.

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fold fold [option] [files]
Break the lines of the named files so that they are no wider than the specified width (default is 80). fold breaks
lines exactly at the specified width, even in the middle of a word. Reads from standard input when given -as a
file.

Options
-b, --bytes
Count bytes, not columns (i. e., consider tabs, backspaces, and carriage returns to be one column).
-s, --spaces
Break at spaces only, if possible.
-w, --width width
Set the maximum line width to width. Default is 80.

formail formail [options]
Filter standard input into mailbox format. If no sender is apparent, provide the sender foo@ bar. By default,
escape bogus From lines with >.

Options
+skip
Do not split first skip messages.
-total
Stop after splitting total messages.
-a headerfield
Append headerfield to header, unless it already exists. If headerfield is Message-ID or Resent-Message-ID
with no contents, generate a unique message ID.

-b
Do not escape bogus From lines.
-c
When header fields are more than one line long, concatenate the lines.
-d
Do not assume that input must be in strict mailbox format.
-e
Allow messages to begin one immediately after the other; do not require empty space between them.
-f
Do not edit non-mailbox-format lines. By default, formail prepends From to such lines.

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-i headerfield

Append headerfield whether or not it already exists. Rename each existing headerfield to Old-headerfield,
unless they are empty.

-k
For use only with -r. Keep the body as well as the fields specified by -r.
-m minfields
Require at least minfields before recognizing the beginning of a new message. Default is 2.
-n
Allow simultaneous formail processes to run.
-p prefix
Escape lines with prefix instead of >.
-q
Do not display write errors, duplicate messages, and mismatched Content-Length fields. This is the
default; use -q-to turn it off.

-r
Throw away all existing fields, retaining only X-Loop, and generate autoreply header instead. You can
preserve particular fields with the -i option.

-s
Must be the last option; everything following it will be assumed to be its arguments. Divide input to
separate mail messages, and pipe them to the program specified or concatenate them to standard output
(by default).

-t
Assume sender's return address to be valid. (By default, formail favors machine-generated addresses.)
-u headerfield
Delete all but the first occurrence of headerfield.
-x headerfield
Display the contents of headerfield on a single line.
-z
When necessary, add a space between field names and contents. Remove (" zap") empty fields.
-A headerfield
Append headerfield whether or not it already exists.
-B
Assume that input is in BABYL rmail format.

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-D maxlen idcache

Remember old message IDs (in idcache, which will grow no larger than approximately maxlen). When
splitting, refuse to output duplicate messages. Otherwise, return true on discovering a duplicate. With -r,
look at the sender's mail address instead of the message ID.

-I headerfield
Append headerfield whether or not it already exists. Remove existing fields.
-R oldfield newfield
Change all fields named oldfield to newfield.
-U headerfield
Delete all but the last occurrence of headerfield.
-Y
Format in traditional Berkeley style (i. e., ignore Content-Length fields).
-X headerfield
Display the field name and contents of headerfield on a single line.

free free [options]
Display statistics about memory usage: total free, used, physical, swap, shared, and buffers used by the kernel.
Options
-b
Calculate memory in bytes.
-k
Default. Calculate memory in kilobytes.
-m
Calculate memory in megabytes.
-o
Do not display "buffer adjusted" line. The -o switch disables the display "-/+ buffers" line.
-s time
Check memory usage every time seconds.
-t
Display all totals on one line at the bottom of output.
-V
Display version information.

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fsck fsck [options] [filesystem] ...
System administration command. Call the filesystem checker for the appropriate system type, to check and
repair filesystems. If a filesystem is consistent, the number of files, number of blocks used, and number of
blocks free are reported. If a filesystem is inconsistent, fsck prompts before each correction is attempted. fsck's
exit code can be interpreted as the sum of all of those conditions that apply:

1
Errors were found and corrected.
2
Reboot suggested.
4
Errors were found but not corrected.
8
fsck encountered an operational error.
16
fsck was called incorrectly.
128
A shared library error was detected.
Options
--
Pass all subsequent options to filesystem-specific checker. All options that fsck doesn't recognize will
also be passed.

-r
Interactive mode; prompt before making any repairs.
-s
Serial mode.
-t fstype
Specify the filesystem type. Do not check filesystems of any other type.
-A
Check all filesystems listed in /etc/ fstab.
-N
Suppress normal execution; just display what would be done.
-R

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Meaningful only with -A: check all filesystems listed in /etc/ fstab except the root filesystem.

-T
Suppress printing of title.
-V
Verbose mode.

fsck. minix fsck. minix [options] device
System administration command. Similar to fsck, but specifically intended for Linux MINIX filesystems.
Options
-a
Automatic mode; repair without prompting.
-f
Force checking, even if kernel has already marked the filesystem. fsck. minix will normally exit without
checking if the system appears to be clean.

-l
List filesystems.
-m
Enable MINIX-like "mode not cleared" warnings.
-r
Interactive mode; prompt before making any repairs.
-s
Display information about superblocks.
-v
Verbose mode.

ftp ftp [options] [hostname]
Transfer files to and from remote network site hostname. ftp prompts the user for a command. The commands
are listed after the options. Some of the commands are toggles, meaning they turn on a feature when it is off and
vice versa.

Options
-d
Enable debugging.
-g

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Disable filename globbing.

-i
Turn off interactive prompting.
-n
No autologin upon initial connection.
-v
Verbose. Show all responses from remote server.
Commands
![ command [args]]
Invoke an interactive shell on the local machine. If arguments are given, the first is taken as a command
to execute directly, with the rest of the arguments as that command's arguments.

$ macro-name [args]
Execute the macro macro-name that was defined with the macdef command. Arguments are passed to the
macro unglobbed.

account [passwd]
Supply a supplemental password that will be required by a remote system for access to resources once a
login has been successfully completed. If no argument is given, the user will be prompted for an account
password in a nonechoing mode.

append local-file [remote-file]
Append a local file to a file on the remote machine. If remote-file is not given, the local filename is used
after being altered by any ntrans or nmap setting. File transfer uses the current settings for type, format,
mode, and structure.

ascii
Set the file transfer type to network ASCII (default).
bell
Sound a bell after each file transfer command is completed.
binary
Set file transfer type to support binary image transfer.
bye
Terminate FTP session and then exit ftp.
case
Toggle remote computer filename case mapping during mget. The default is off. When case is on, files
on the remote machine with all-uppercase names will be copied to the local machine with all-lowercase
names.

cd remote-directory

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Change working directory on remote machine to remote-directory.
cdup
Change working directory of remote machine to its parent directory.
chmod [mode] [remote-file]
Change file permissions of remote-file. If options are omitted, the command prompts for them.
close
Terminate FTP session and return to command interpreter.
cr
Toggle carriage return stripping during ASCII-type file retrieval.
delete remote-file
Delete file remote-file on remote machine.
debug [debug-value]
Toggle debugging mode. If debug-value is specified, it is used to set the debugging level.
dir [remote-directory] [local-file]
Print a listing of the contents in the directory remote-directory, and, optionally, place the output in local-file.
If no directory is specified, the current working directory on the remote machine is used. If no local
file is specified or -is given instead of the filename, output comes to the terminal.

disconnect
Synonym for close.
form format
Set the file transfer form to format. Default format is file.
get remote-file [local-file]
Retrieve the remote-file and store it on the local machine. If the local filename is not specified, it is given
the same name it has on the remote machine, subject to alteration by the current case, ntrans, and nmap
settings. If local file is -, output comes to the terminal.

glob
Toggle filename expansion for mdelete, mget, and mput. If globbing is turned off, the filename
arguments are taken literally and not expanded.

hash
Toggle hash-sign (#) printing for each data block transferred.
help [command]
Print help information for command. With no argument, ftp prints a list of commands.
idle [seconds]

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Get/ set idle timer on remote machine. seconds specifies the length of the idle timer; if omitted, the current
idle timer is displayed.

image
Same as binary.
lcd [directory]
Change working directory on local machine. If directory is not specified, the user's home directory is
used.

ls [remote-directory] [local-file]
Print listing of contents of directory on remote machine, in a format chosen by the remote machine. If
remote-directory is not specified, current working directory is used.

macdef macro-name
Define a macro. Subsequent lines are stored as the macro macro-name; a null line terminates macro input
mode. When $i is included in the macro, loop through arguments, substituting the current argument for $i
on each pass. Escape $ with \.

mdelete remote-files
Delete the remote-files on the remote machine.
mdir remote-files local-file
Like dir, except multiple remote files may be specified.
mget remote-files
Expand the wildcard expression remote-files on the remote machine and do a get for each filename thus
produced.

mkdir directory-name
Make a directory on the remote machine.
mls remote-files local-file
Like nlist, except multiple remote files may be specified, and the local file must be specified.
mode [mode-name]
Set file transfer mode to mode-name. Default mode is stream mode.
modtime [file-name]
Show last modification time of the file on the remote machine.
mput [local-files]
Expand wildcards in local-files given as arguments and do a put for each file in the resulting list.
newer remote-file [local-file]
Get file if remote file is newer than local file.

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nlist [remote-directory] [local-file]

Print list of files of a directory on the remote machine to local-file (or the screen if local-file is not
specified). If remote-directory is unspecified, the current working directory is used.

nmap [inpattern outpattern]
Set or unset the filename mapping mechanism. The mapping follows the pattern set by inpattern, a
template for incoming filenames, and outpattern, which determines the resulting mapped filename. The
sequences $1 through $9 are treated as variables, for example, the inpattern $1.$ 2, along with the input
file readme. txt, would set $1 to readme and $2 to txt. An outpattern of $1. data would result in an output
file of readme. data. $0 corresponds to the complete filename. [string1, string2] is replaced by string1,
unless that string is null, in which case it's replaced by string2.

ntrans [inchars [outchars ]]
Set or unset the filename character translation mechanism. Characters in a filename matching a character
in inchars are replaced with the corresponding character in outchars. If no arguments are specified, the
filename mapping mechanism is unset. If arguments are specified:

m Characters in remote filenames are translated during mput and put commands issued without a
specified remote target filename.

m Characters in local filenames are translated during mget and get commands issued without a
specified local target filename.

open host [port]
Establish a connection to the specified host FTP server. An optional port number may be supplied, in
which case ftp will attempt to contact an FTP server at that port.

prompt
Toggle interactive prompting.
proxy ftp-command
Execute an FTP command on a secondary control connection (i. e., send commands to two separate
remote hosts simultaneously).

put local-file [remote-file]
Store a local file on the remote machine. If remote-file is left unspecified, the local filename is used after
processing according to any ntrans or nmap settings in naming the remote file. File transfer uses the
current settings for type, file, structure, and transfer mode.

pwd
Print name of the current working directory on the remote machine.
quit
Synonym for bye.
quote arg1 arg2...
Send the arguments specified, verbatim, to the remote FTP server.
recv remote-file [local-file]
Synonym for get.

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reget remote-file [local-file]

Retrieve a file (like get), but restart at the end of local-file. Useful for restarting a dropped transfer.
remotehelp [command-name]
Request help from the remote FTP server. If command-name is specified, remote help for that command
is returned.

remotestatus [filename]
Show status of the remote machine, or, if filename is specified, filename on remote machine.
rename [from] [to]
Rename file from on remote machine to to.
reset
Clear reply queue.
restart marker
Restart the transfer of a file from a particular byte count.
rmdir [directory-name]
Delete a directory on the remote machine.
runique
Toggle storing of files on the local system with unique filenames. When this option is on, rename files as
.1 or .2, and soon, as appropriate, to preserve unique filenames, and report each such action. Default value
is off.

send local-file [remote-file]
Synonym for put.
sendport
Toggle the use of PORT commands.
site [command]
Get/ set site-specific information from/ on remote machine.
size filename
Return size of filename on remote machine.
status
Show current status of ftp.
struct [struct-name]
Set the file transfer structure to struct-name. By default, stream structure is used.
sunique

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Toggle storing of files on remote machine under unique filenames.

system
Show type of operating system running on remote machine.
tenex
Set file transfer type to that needed to talk to TENEX machines.
trace
Toggle packet tracing.
type [type-name]
Set file transfer type to type-name. If no type is specified, the current type is printed. The default type is
network ASCII.

umask [mask]
Set user file-creation mode mask on the remote site. If mask is omitted, the current value of the mask is
printed.

user username [password] [account]
Identify yourself to the remote FTP server. ftp will prompt the user for the password, if not specified and
the server requires it, and the account field.

verbose
Toggle verbose mode.
? [command]
Same as help.

ftpd in. ftpd [options]
TCP/ IP command. Internet File Transfer Protocol server. The server uses the TCP protocol and listens at the port
specified in the ftp service specification. ftpd is started by inetd and must have an entry in inetd's configuration
file, /etc/ inetd. conf.

Options
-d
Write debugging information to the syslog.
-l

Log each FTP session in the syslog.
-Tmaxtimeout

Set maximum timeout period in seconds. Default limit is 15 minutes.
-ttimeout

Set timeout period to timeout seconds.

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fuser fuser [options] [files | filesystems]
Identify processes that are using a file or filesystem. fuser outputs the process IDs of the processes that are using
the files or local filesystems. Each process ID is followed by a letter code: c if process is using file as current
directory, e if executable, f if an open file, m if a shared library, and r if the root directory. Any user with
permission to read /dev/ kmem and /dev/ mem can use fuser, but only a privileged user can terminate another
user's process. fuser does not work on remote (NFS) files.

If more than one group of files is specified, the options may be respecified for each additional group of files. A
lone dash (-) cancels the options currently in force, and the new set of options applies to the next group of files.

Options
-Return
all options to defaults.
-signal
Send signal instead of SIGKILL.
-a
Display information on all specified files, even if they are not being accessed by any processes.
-i
Request user confirmation to kill a process. Ignored if -k is not also specified.
-k
Send SIGKILL signal to each process.
-l
List signal names.
-m
Expect files to exist on a mounted filesystem; include all files accessing that filesystem.
-s
Silent.
-u
User login name, in parentheses, also follows process ID.
-v
Verbose.
-V
Display version information.

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g++ g++ [options] files
Invoke gcc with the options necessary to make it recognize C++. g++ recognizes all the file extensions gcc does,
in addition to C++ source files (. C, .cc, or .cxx files) and C++ preprocessed files (. ii files). See also gcc.

gated gated [options]
TCP/ IP command. Gateway routing daemon. gated handles multiple routing protocols and replaces routed and
any routing daemons that speak the Hello, EGP, or BGP routing protocols. gated currently handles the RIP,
BGP, EGP, Hello, and OSPF routing protocols and can be configured to perform all or any combination of the
five.

Options
-c
Parse configuration file for syntax errors, then exit gated, leaving a dump file in /usr/ tmp/ gated_ dump.
-f config_ file
Use alternate configuration file, config_ file. Default is /etc/ gated. conf.
-n
Do not modify kernel's routing table.
-t [trace_ options]
Start gated with the specified tracing options enabled. If no flags are specified, assume general. The
trace flags are:

adv
Management of policy blocks.
all
Includes normal, policy, route, state, task, and timer.
general
Includes normal and route.
iflist
The kernel interface list.
normal
Normal protocols instances.
parse
Lexical analyzer and parser.
policy
Instances in which policy is applied to imported and exported routes.
route
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Any changes to routing table.
state
State machine transitions.
symbols
Symbols read from kernel --note that they are read before the configuration file is parsed, so this
option must be specified on the command line.

task
System tasks and interfaces.
timer
Timer usage.
-C
Parse configuration file for errors and set exit code to indicate if there were any (1) or not (0), then exit.
-N
Do not daemonize.

gawk gawk [options] `script' [var= value...] [files]
gawk [options] -f scriptfile [var= value...] [files]
The GNU version of awk, a program that does pattern matching, record processing, and other forms of text
manipulation. For more information, see Chapter 13, "The gawk Scripting Language".

gcc gcc [options] files
Compile one or more C source files (file. c), assembler source files (file. s), or preprocessed C source files (file. i).
If the file suffix is not recognizable, assume that the file is an object file or library. gcc automatically invokes the
link editor ld (unless -c, -S, or -E is supplied). In some cases, gcc generates an object file having a .o suffix and a
corresponding root name. By default, output is placed in a. out. gcc accepts many system-specific options not
covered here.

Note: gcc is the GNU form of cc; on most Linux systems, the command cc will invoke gcc. The command g++
will invoke gcc with the appropriate options for interpreting C++.

Options
-a
Provide profile information for basic blocks.
-ansi
Enforce full ANSI conformance.
-b machine
Compile for use on machine type.

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-c
Create linkable object file for each source file, but do not call linker.
-dD
Print #defines.
-dM
Suppress normal output. Print series of #defines that are in effect at the end of preprocessing.
-dN
Print #defines with macro names only, not arguments or values.
-fno-asm
Do not recognize asm, inline, or typeof as keywords. Implied by -ansi.
-fno-builtin
Do not recognize built-in functions unless they begin with two underscores.
-fno-gnu-keywords
Do not recognize classof, headof, signature, sigof, or typeof as keywords.
-fno-ident
Do not respond to #ident commands.
-fsigned-bitfields
-funsigned-bitfields
-fno-signed-bitfields
-fno-unsigned-bitfields

Set default control of bitfields to signed or unsigned if not explicitly declared.
-fsigned-char
Cause the type char to be signed.
-fsyntax-only
Check for syntax errors. Do not attempt to actually compile.
-funsigned-char
Cause the type char to be unsigned.
-g
Include debugging information for use with gdb.
-glevel
Provide level amount of debugging information. level must be 1, 2, or 3, with 1 providing the least
amount of information. The default is 2.

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-idirafter dir

Include dir in the list of directories to search when an include file is not found in the normal include path.
-include file
Process file before proceeding to the normal input file.
-imacros file
Process the macros in file before proceeding to the normal input file.
-iprefix prefix
When adding directories with -iwithprefix, prepend prefix to the directory's name.
-isystem dir
Add dir to the list of directories to be searched when a system file cannot be found in the main include
path.

-iwithprefix dir
Append dir to the list of directories to be searched when a header file cannot be found in the main include
path. If -iprefix has been set, prepend that prefix to the directory's name.

-llib
Link to lib.
-nostartfiles
Force linker to ignore standard system startup files.
-nostdinc
Search only specified, not standard, directories for header files.
-nostdinc++
Suppress searching of directories believed to contain C++-specific header files.
-nostdlib
Suppress linking to standard library files.
-o file
Specify output file as file. Default is a. out.
-p
Provide profile information for use with prof.
-pedantic
Warn verbosely.
-pedantic-errors
Err in every case in which -pedantic would have produced a warning.

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-pg
Provide profile information for use with gprof.
-pipe
Transfer information between stages of compiler by pipes instead of temporary files.
-s
Remove all symbol table and relocation information from the executable.
-save-temps
Save temporary files in the current directory when compiling.
-static
Suppress linking to shared libraries.
-traditional
Attempt to behave like a traditional C compiler.
-traditional-cpp
Cause the preprocessor to attempt to behave like a traditional C preprocessor.
-trigraphs
Include trigraph support.
-u symbol
Force the linker to search libraries for a definition of symbol and to link to them, if found.
-undef
Define only those constants required by the language standard, not system-specific constants like unix.
-v
Verbose mode. Display commands as they are executed, gcc version number, and preprocessor version
number.

-w
Suppress warnings.
-x language
Expect input file to be written in language, which may be c, objective-c, c-header, c++, cpp-output,
assembler, or assembler-with-cpp. If none is specified as language, guess the language by filename
extension.

-Aquestion( answer)
If the preprocessor encounters a conditional such as #if question, assert answer in response. To turn off
standard assertions, use -A-.

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-Bpath

Specify the path directory in which the compiler files are located.
-C
Retain comments during preprocessing. Meaningful only with -E.
-Dname[= def]
Define name with value def as if by a #define. If no =def is given, name is defined with value 1. -D has
lower precedence than -U.

-E
Preprocess the source files, but do not compile. Print result to standard output.
-Idir
Include dir in list of directories to search for include files. If dir is -, search those directories that were
specified by -I before the -I-only when #include "file" is specified, not #include <file>.

-Ldir
Search dir in addition to standard directories.
-M
Instead of compiling, print a rule suitable for inclusion in a makefile that describes dependencies of the
source file based on its #include directives. Implies -E.

-MD
Similar to -M, but sends dependency information to files ending in .d in addition to ordinary compilation.
-MG
Used with -M or -MM. Suppress error messages if an included file does not exist; useful if the included
file is automatically generated by a build.

-MMD
Similar to -MD, but record only user header file information, not system header file information.
-MM
Similar to -M, but limit the rule to non-standard #include files; that is, only files declared through
#include "file" and not those declared through #include <file>.

-H
Print pathnames of included files, one per line, on standard error.
-O[ level]
Optimize. level should be 1, 2, 3, or 0. The default is 1. 0 turns off optimization; 3 optimizes the most.
-P
Preprocess input without producing line-control information used by next pass of C compiler. Meaningful
only with -E.

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-S
Compile source files into assembler code, but do not assemble.
-Uname
Remove any initial definition of name, where name is a reserved symbol predefined by the preprocessor
or a name defined on a -D option. Names predefined by cpp are unix and i386.

-V version
Attempt to run gcc version version.
-W
Warn more verbosely than normal.
-Wl, option
Invoke linker with option, which may be a comma-separated list.
-Wa, option
Call assembler with option, which may be a comma-separated list.
-Waggregate-return
Warn if any functions return structures or unions are defined or called.
-Wall
Enable -W, -Wchar-subscripts, -Wcomment, -Wformat, -Wimplicit, -Wparentheses, -Wreturn-type,
-Wswitch, -Wtemplate-debugging, -Wtrigraphs, -Wuninitialized, and -Wunused.

-Wcast-align
Warn when encountering instances in which pointers are cast to types that increase the required
alignment of the target from its original definition.

-Wcast-qual
Warn when encountering instances in which pointers are cast to types that lack the type qualifier with
which the pointer was originally defined.

-Wchar-subscripts
Warn when encountering arrays with subscripts of type char.
-Wcomment
Warn when encountering the beginning of a nested comment.
-Wconversion
Warn in particular cases of type conversions.
-Werror
Exit at the first error.

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-Wformat

Warn about inappropriately formatted printfs and scanfs.
-Wimplicit
Warn when encountering implicit function or parameter declarations.
-Winline
Warn about illegal inline functions.
-Wmissing-declarations
Warn if a global function is defined without a previous declaration.
-Wmissing-prototypes
Warn when encountering global function definitions without previous prototype declarations.
-Wnested-externs
Warn if an extern declaration is encountered within a function.
-Wno-import
Don't warn about use of #import.
-Wp, options
Pass options to the preprocessor. Multiple options are separated by commas. Not a warning parameter.
-Wparentheses
Enable more verbose warnings about omitted parentheses.
-Wpointer-arith
Warn when encountering code that attempts to determine the size of a function or void.
-Wredundant-decls
Warn if anything is declared more than once in the same scope.
-Wreturn-type
Warn about functions defined without return types or with improper return types.
-Wshadow
Warn when a local variable shadows another local variable.
-Wstrict-prototypes
Insist that argument types be specified in function declarations and definitions.
-Wswitch
Warn about switches that skip the index for one of their enumerated types.
-Wtemplate-debugging
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Warn if debugging is not available for C++ templates.
-Wtraditional
Warn when encountering code that produces different results in ANSI C and traditional C.
-Wtrigraphs
Warn when encountering trigraphs.
-Wuninitialized
Warn when encountering uninitialized automatic variables.
-Wunused
Warn about unused variables and functions.
-Xlinker option
Pass an option to the linker. A linker option with an argument requires two -Xs, the first specifying the
option and the second specifying the argument.

Pragma directives
#pragma interface [header-file]
Used in header files to force object files to provide definition information via references, instead of
including it locally in each file. C++-specific.

#pragma implementation [header-file]
Used in main input files to force generation of full output from header-file (or, if it is not specified, from
the header file with the same base name as the file containing the pragma directive). This information will
be globally visible. Normally the specified header file contains a #pragma interface directive.

gdb gdb [options] [program [core| pid]]
GDB (GNU DeBugger) allows you to step through C, C++, and Modula-2 programs in order to find the point at
which they break. The program to be debugged is normally specified on the command line; you can also specify
a core or, if you want to investigate a running program, a process ID.

Options
-s file, -symbols= file
Consult file for symbol table. With -e, also uses file as the executable.
-e file, -exec= file
Use file as executable, to be read in conjunction with source code. May be used in conjunction with -s to
read symbol table from the executable.

-c file, -core= file
Consult file for information provided by a core dump.
-x file, -command= file

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Read gdb commands from file.

-d directory, -directory= directory
Include directory in path that is searched for source files.
-n, -nx
Ignore .gdbinit file.
-q, -quiet
Suppress introductory and copyright messages.
-batch
Exit after executing all the commands specified in .gdbinit and -x files. Print no startup messages.
-cd= directory
Use directory as gdb's working directory.
-f, -fullname
Show full filename and line number for each stack frame.
-b bps
Set line speed of serial device used by GDB to bps.
-tty= device
Set standard in and standard out to device.
Common commands
These are just some of the more common gdb commands; there are too many commands to list all of them here:
bt
Print the current location within the program and a stack trace showing how the current location was
reached. (where does the same thing.)

break
Set a breakpoint in the program.
cd
Change the current working directory.
clear
Delete the breakpoint where you just stopped.
commands
List commands to be executed when breakpoint is hit.
c

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Continue execution from a breakpoint.

delete
Delete a breakpoint or a watchpoint; also used in conjunction with other commands.
display
Cause variables or expressions to be displayed when program stops.
down
Move down one stack frame to make another function the current one.
frame
Select a frame for the next continue command.
info
Show a variety of information about the program. For instance, info breakpoints shows all outstanding
breakpoints and watchpoints.

jump
Start execution at another point in the source file.
kill
Abort the process running under gdb's control.
list
List the contents of the source file corresponding to the program being executed.
next
Execute the next source line, executing a function in its entirety.
print
Print the value of a variable or expression.
pwd
Show the current working directory.
ptype
Show the contents of a datatype, such as a structure or C++ class.
quit
Exit gdb.
reverse-search
Search backward for a regular expression in the source file.
run

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Execute the program.

search
Search for a regular expression in the source file.
set variable
Assign a value to a variable.
signal
Send a signal to the running process.
step
Execute the next source line, stepping into a function if necessary.
undisplay
Reverse the effect of the display command; keep expressions from being displayed.
until
Finish the current loop.
up
Move up one stack frame to make another function the current one.
watch
Set a watchpoint (i. e., a data breakpoint) in the program.
whatis
Print the type of a variable or function.

gdc gdc [options] command
TCP/ IP command. Administer gated. Various commands start and stop the daemon, send signals to it, maintain
the configuration files, and manage state and core dumps.

Options
-c size
Specify maximum core dump size.
-f size
Specify maximum file dump size.
-m size
Specify maximum data segment size.
-n
Suppress editing of the kernel forwarding table.

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-q
Quiet mode: suppress warnings and log errors to syslogd instead of standard error.
-s size
Specify maximum stack size.
-t seconds
Wait seconds seconds (default is 10) for gated to complete specified operations at start and stop time.
Commands
BACKOUT
Restore /etc/ gated. conf from /etc/ gated. conf-, whether or not the latter exists.
backout
Restore /etc/ gated. conf from /etc/ gated. conf-, assuming the latter exists.
checkconf
Report any syntax errors in /etc/ gated. conf.
checknew
Report any syntax errors in /etc/ gated. conf+.
COREDUMP
Force gated to core dump and exit.
createconf
Create an empty /etc/ gated. conf+ if one does not already exist, and set it to mode 664, owner root, group
gdmaint.

dump
Force gated to dump to /usr/ tmp/ gated_ dump and then continue normal operation.
interface
Reload interface configuration.
KILL
Terminate immediately (ungracefully).
modeconf
Set all configuration files to mode 664, owner root, group gdmaint.
newconf
Make sure that /etc/ gated. conf+ exists and move it to /etc/ gated. conf. Save the old /etc/ gated. conf as
/etc/ gated. conf-.

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reconfig

Reload configuration file.
restart
Stop and restart gated.
rmcore
Remove any gated core files.
rmdmp
Remove any gated state dump files.
rmparse
Remove any gated files that report on parse errors. These are generated by the checkconf and checknew
commands.

running
Exit with zero status if gated is running and nonzero if it is not.
start
Start gated, unless it is already running, in which case return an error.
stop
Stop gated as gracefully as possible.
term
Terminate gracefully.
toggletrace
Toggle tracing.
Files
/etc/ gcd. conf+
The test configuration file. Once you're satisfied that it works, you should run gated newconf to install it
as /etc/ gated. conf.

/etc/ gated. conf-A
backup of the old configuration file.
/etc/ gated. conf--
A backup of the backup of the old configuration file.
/etc/ gated. conf
The actual configuration file.
/etc/ gated. pid
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gated's process ID.
/usr/ tmp/ gated_ dump
The state dump file.
/usr/ tmp/ gated_ parse
A list of the parse errors generated by reading the configuration file.

getkeycodes getkeycodes
Print the kernel's scancode-to-keycode mapping table.

getty getty [options] port [speed [term [lined]]]
System administration command. Set terminal type, modes, speed, and line discipline. Linux systems may use
agetty instead, which uses a different syntax. getty is invoked by init. It is the second process in the series init-getty-
login-shell, which ultimately connects a user with the Linux system. getty reads the user's login name and
invokes the login command with the user's name as an argument. While reading the name, getty attempts to
adapt the system to the speed and type of device being used.

You must specify a port argument, which getty will use to attach itself to the device /dev/ port. getty will then
scan the defaults file, usually /etc/ default/ getty, for runtime values and parameters. These may also be specified,
for the most part, on the command line, but the values in the defaults file take precedence. The speed argument is
used to point to an entry in the file /etc/ gettydefs, which contains the initial baud rate, tty settings, and login
prompt and final speed and settings for the connection. The first entry is the default in /etc/ gettydefs. term
specifies the type of terminal, with lined the optional line discipline to use.

Options
-c file
Check the gettydefs file. file is the name of the gettydefs file. Produces the files' values and reports parsing
errors to standard output.

-d file
Use a different default file.
-h
Do not force a hangup on the port when initializing.
-r delay
Wait for single character from port, then wait delay seconds before proceeding.
-t timeout
If no username is accepted within timeout seconds, close connection.
-w string
Wait for string characters from port before proceeding.

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gprof gprof [options] [object_ file]
Display the profile data for an object file. The file's symbol table is compared with the call graph profile file
gmon. out (previously created by compiling with gcc -pg).

Options
-a
Do not display statically declared functions. Since their information might still be relevant, append it to
the information about the functions loaded immediately before.

-b
Do not display information about each field in the profile.
-c
Consult the object file's text area to attempt to determine the program's static call graph. Display static-only
parents and children with call counts of 0.

-e routine
Do not display entries for routine and its descendants.
-f routine
Print only routine, but include time spent in all routines.
-k from to
Remove arcs between the routines from and to.
-s
Summarize profile information in the file gmon. sum.
-v
Print version and exit.
-z
Include zero-usage calls.
-E routine
Do not display entries for routine and its descendants or include time spent on them in calculations for
total time.

-F routine
Print only information about routine. Do not include time spent in other routines.

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grep grep [options] pattern [files]
Search one or more files for lines that match a regular expression pattern. Regular expressions are described in
Chapter 9, "Pattern Matching". Exit status is 0 if any lines match, 1 if none match, and 2 for errors. See also

egrep and fgrep.

Options
-a, --text
Don't suppress output lines with binary data; treat as text.
-b, --byte-offset

Print the byte offset within the input file before each line of output.
-b, --byte-offset

Print the byte offset within the input file before each line of output.
-c, --count

Print only a count of matched lines. With -v or --revert-match option, count nonmatching lines.
-d action, --directories= action

Define an action for processing directories. Possible actions are:
read
Read directories like ordinary files (default).
skip

Skip directories.
recurse

Recursively read all files under each directory. Same as -r.
-e pattern, --regexp= pattern

Search for pattern. Same as specifying a pattern as an argument, but useful in protecting patterns
beginning with -.
-f file, --file= file

Take a list of patterns from file, one per line.
-h, --no-filename

Print matched lines but not filenames (inverse of -l).
-i, --ignore-case

Ignore uppercase and lowercase distinctions.
-l, --files-with-matches

List the names of files with matches but not individual matched lines; scanning per file stops on the first
match.
-n, --line-number

Print lines and their line numbers.
-q, --quiet, --silent

Suppress normal output in favor of quiet mode; the scanning stops on the first match.
-r, --recursive

Recursively read all files under each directory. Same as -d recurse.
-s, --no-messages

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Suppress error messages about nonexistent or unreadable files.
-v, --revert-match

Print all lines that don't match pattern.
-w, --word-regexp

Match on whole words only. Words are divided by characters that are not letters, digits, or underscores.
-x, --line-regexp

Print lines only if pattern matches the entire line.
-A num, --after-context= num

Print num lines of text that occur after the matching line.
-B num, --before-context= num

Print num lines of text that occur before the matching line.
-C[ num], --context=[ num], -num

Print num lines of leading and trailing context. Default context is 2 lines.
-L, --files-without-match

List files that contain no matching lines.
-V, --version

Print the version number and then exit.
Examples
List the number of users who use tcsh:
grep -c /bin/ tcsh /etc/ passwdList header files that have at least one #include directive:
grep -l '^# include' /usr/ include/*List files that don't contain pattern:
grep -c pattern files | grep :0

groff groff [options] [files]
troff [options] [files]
Frontend to the groff document-formatting system, which normally runs troff along with a postprocessor
appropriate for the selected output device. Options without arguments can be grouped after a single dash (-). A
filename of -denotes standard input.

Options
-a
Generate an ASCII approximation of the typeset output.
-b
Print a backtrace.
-C

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Enable compatibility mode.

-dcs, -dname= s
Define the character c or string name to be the string s.
-e
Preprocess with eqn.
-E
Don't print any error messages.
-ffam
Use fam as the default font family.
-Fdir
Search dir for subdirectories with DESC and font files before the default /usr/ lib/ groff/ font.
-h
Print a help message.
-i
Read standard input after all files have been processed.
-l
Send the output to a printer (as specified by the print command in the device description file).
-Larg
Pass arg to the spooler. Each argument should be passed with a separate -L option.
-mname
Read the macro file tmac. name.
-Mdir
Search directory dir for macro files before the default directory /usr/ lib/ groff/ tmac.
-nnum
Set the first page number to num.
-N
Don't allow newlines with eqn delimiters; equivalent to eqn's -N option.
-olist
Output only pages specified in list, which is a comma-separated list of page ranges.
-p
Preprocess with pic.
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-Parg
Pass arg to the postprocessor. Each argument should be passed with a separate -P option.
-rcn, -name= n
Set the number register c or name to n. c is a single character and n is any troff numeric expression.
-R
Preprocess with refer.
-s
Preprocess with soelim.
-S
Use safer mode (i. e., pass the -S option to pic and use the -msafer macros with troff).
-t
Preprocess with tbl.
-Tdev
Prepare output for device dev; the default is ps.
-v
Make programs run by groff print out their version number.
-V
Print the pipeline on stdout instead of executing it.
-wname
Enable warning name. You can specify multiple -w options. See the troff manpage for a list of warnings.
-Wname
Disable warning name. You can specify multiple -W options. See the troff manpage for a list of
warnings.

-z
Suppress troff output (except error messages).
-Z
Do not postprocess troff output. Normally groff automatically runs the appropriate postprocessor.
Devices
ascii
Typewriter-like device

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dvi

TeX dvi format
latin1
Typewriter-like devices using the ISO Latin-1 character set
ps
PostScript
X75
75-dpi X11 previewer
X100
100-dpi X11 previewer
lj4
HP LaserJet4-compatible (or other PCL5-compatible) printer
Environment variables
GROFF_ COMMAND_ PREFIX
If set to be X, groff will run Xtroff instead of troff.
GROFF_ FONT_ PATH
Colon-separated list of directories in which to search for the devname directory.
GROFF_ TMAC_ PATH
Colon-separated list of directories in which to search for the macro files.
GROFF_ TMPDIR
If set, temporary files will be created in this directory; otherwise, they will be created in TMPDIR (if set)
or /tmp (if TMPDIR is not set).

GROFF_ TYPESETTER
Default device.
PATH
Search path for commands that groff executes.

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groupadd groupadd [options] group
System administration command. Create new group account group.
Options
-ggid
Assign numerical group ID. (By default, the first available number above 500 is used.) The value must be
unique unless the -o option is used.

-o
Accept a nonunique gid with the -g option.

groupdel groupdel group
System administration command. Remove group from system account files. You may still need to find and
change permissions on files that belong to the removed group.

groupmod groupmod [options] group
System administration command. Modify group information for group.
Options
-g gid
Change the numerical value of the group ID. Any files that have the old gid will have to be changed
manually. The new gid must be unique unless the -o option is used.

-n name
Change the group name to name.
-o
Override. Accept a nonunique gid.

groups groups [options] [users]
Show the groups that each user belongs to (default user is the owner of the current group). Groups are listed in
/etc/ passwd and /etc/ group.

Options
--help
Print help message.
--version
Print version information.

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grpck grpck [option] [files]
System administration command. Remove corrupt or duplicate entries in the /etc/ group and /etc/ gshadow files.
Generate warnings for other errors found. grpck will prompt for a "yes" or "no" before deleting entries. If the
user replies "no," the program will exit. If run in a noninteractive mode, the reply to all prompts is "no."
Alternate group and gshadow files can be checked. If other errors are found, the user will be encouraged to run
the groupmod command.

Option
-n
Noninteractive mode.
Exit codes
0
Success.
1
Syntax error.
2
One or more bad group entries found.
3
Could not open group files.
4
Could not lock group files.
5
Could not write group files.

grpconv grpconv
grpunconv
System administration command. Like pwconv, the grpconv command creates a shadowed group file to keep
your encrypted group passwords safe from password cracking programs. grpconv creates the /etc/ gshadow file
based on your existing /etc/ groups file and replaces your encrypted password entries with x. If you add new
entries to the /etc/ groups file, you can run grpconv again to transfer the new information to /etc/ gshadow. It will
ignore entries that already have a password of x and convert those that do not. grpunconv restores the encrypted
passwords to your /etc/ groups file and removes the /etc/ gshadow file.

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gs gs [options] [files]
An interpreter for Adobe Systems' PostScript and PDF (Portable Document Format) languages; used for
document processing. With -in place of files, standard input is used.

Options
--filename arg1 ...
Take the next argument as a filename, but use all remaining arguments to define ARGUMENTS in
userdict (not systemdict) as an array of those strings, before running the file.

-gnumber1xnumber2
Specify width and height of device; intended for systems like the X Window System.
-q
Quiet startup.
-rnumber, -rnumber1xnumber2
Specify X and Y resolutions (for the benefit of devices, such as printers, that support multiple X and Y
resolutions). If only one number is given, it is used for both X and Y resolutions.

-Dname= token, -dname= token
Define a name in systemdict with the given definition. The token must be exactly one token (as defined
by the token operator) and must not contain any whitespace.

-Dname, -dname
Define a name in systemdict with a null value.
-Idirectories
Adds the designated list of directories at the head of the search path for library files.
-Sname= string, -sname= string
Define a name in systemdict with a given string as value.
Special names
-dDISKFONTS
Causes individual character outlines to be loaded from the disk the first time they are encountered.
-dNOBIND
Disables the bind operator. Useful only for debugging.
-dNOCACHE
Disables character caching. Useful only for debugging.
-dNODISPLAY
Suppresses the normal initialization of the output device. May be useful when debugging.

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-dNOPAUSE

Disables the prompt and pause at the end of each page.
-dNOPLATFONTS
Disables the use of fonts supplied by the underlying platform (e. g., the X Window System).
-dSAFER
Disables the deletefile and renamefile operators and the ability to open files in any mode other than read-only.

-dWRITESYSTEMDICT
Leaves systemdict writable.
-sDEVICE= device
Selects an alternate initial output device.
-sOUTPUTFILE= filename
Selects an alternate output file (or pipe) for the initial output device.

gunzip gunzip [options] [files]
Uncompress files compressed by gzip. See gzip for a list of options.

gzexe gzexe [option] [files]
Compress executables. When run, these files automatically uncompress, thus trading time for space. gzexe
creates backup files (filename~), which should be removed after testing the original.

Option
-d
Decompress files.

gzip gzip [options] [files]
gunzip [options] [files]
zcat [options] [files]
Compress specified files (or read from standard input) with Lempel-Ziv coding (LZ77). Rename compressed file
to filename. gz; keep ownership modes and access/ modification times. Ignore symbolic links. Uncompress with
gunzip, which takes all of gzip's options, except those specified. zcat is identical to gunzip -c and takes the
options -fhLV, described here. Files compressed with the compress command can be decompressed using these
commands.

Options
-n, --fast, --best
Regulate the speed of compression using the specified digit n, where -1 or --fast indicates the fastest
compression method (less compression) and -9 or --best indicates the slowest compression method (most
compression). The default compression level is -6.

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-a, --ascii
ASCII text mode: convert end-of-lines using local conventions. This option is supported only on some
non-Unix systems.

-c, --stdout, --to-stdout
Print output to standard output, and do not change input files.
-d, --decompress, --uncompress
Same as gunzip.
-f, --force
Force compression. gzip would normally prompt for permission to continue when the file has multiple
links, its .gz version already exists, or it is reading compressed data to or from a terminal.

-h --help
Display a help screen and then exit.
-l, --list
Expects to be given compressed files as arguments. Files may be compressed by any of the following
methods: gzip, deflate, compress, lzh, and pack. For each file, list uncompressed and compressed sizes
(the latter being always -1 for files compressed by programs other than gzip), compression ratio, and
uncompressed name. With -v, also print compression method, the 32-bit CRC of the uncompressed data,
and the timestamp. With -N, look inside the file for the uncompressed name and timestamp.

-L, --license
Display the gzip license and quit.
-n, --no-name
When compressing, do not save the original filename and timestamp by default. When decompressing, do
not restore the original filename if present, and do not restore the original timestamp if present. This
option is the default when decompressing.

-N, --name
Default. Save original name and timestamp. When decompressing, restore original name and timestamp.
-q, --quiet
Print no warnings.
-r, --recursive
When given a directory as an argument, recursively compress or decompress files within it.
-S suffix, --suffix suffix
Append .suffix. Default is gz. A null suffix while decompressing causes gunzip to attempt to decompress
all specified files, regardless of suffix.

-t, --test
Test compressed file integrity.

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-v, --verbose
Print name and percent size reduction for each file.
-V, --version
Display the version number and compilation options.

halt halt [options]
System administration command. Insert a note in the file /var/ log/ wtmp; if the system is in runlevel 0 or 6, stop
all processes; otherwise, call shutdown -nf.

Options
-d
Suppress writing to /var/ log/ wtmp.
-f
Call halt even when shutdown -nf would normally be called (i. e., force a call to halt, even when not in
runlevel 0 or 6).

-n
Suppress normal call to sync.
-w
Suppress normal execution; simply write to /var/ log/ wtmp.

head head [options] [files]
Print the first few lines (default is 10) of one or more files. If files is missing or -, read from standard input. With
more than one file, print a header for each file.

Options
-c num[ bkm], --bytes num
Print first num bytes or, if num is followed by b, k, or m, first num 512-byte blocks, 1-kilobyte blocks, or
1-megabyte blocks.

--help
Display help and then exit.
-n num, --lines num, -num
Print first num lines. Default is 10.
-q, --quiet, --silent
Quiet mode; never print headers giving filenames.
-v, --verbose
Print filename headers, even for only one file.
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--version
Output version information and then exit.
Examples
Display the first 20 lines of phone_ list:
head -20 phone_ listDisplay the first 10 phone numbers having a 202 area code:
grep '( 202) ' phone_ list | head

host host [options] host [server]
host [options] zone [server]
System administration command. Print information about specified hosts or zones in DNS. Hosts may be IP
addresses or hostnames; host converts IP addresses to hostnames by default and appends the local domain to
hosts without a trailing dot. Default servers are determined in /etc/ resolv. conf. For more information about hosts
and zones, try Chapters 1 and 2 of DNS and BIND by Paul Albitz and Cricket Liu, published by O'Reilly &
Associates.

Options
-a
Same as -t ANY.
-c class
Search for specified resource record class (IN, INTERNET, CS, CSNET, CH, CHAOS, HS, HESIOD,
ANY, or *). Default is IN.

-d
Debugging mode. -dd is a more verbose version.
-e
Do not print information about domains outside of specified zone. For hostname queries, do not print
"additional information" or "authoritative nameserver."

-f file
Output to file as well as standard out.
-i
Given an IP address, return the corresponding in-addr. arpa address, class (always PTR), and hostname.
-l zone
List all machines in zone.
-m
Print only MR, MG, and MB records; recursively expand MR (renamed mail box) and MG (mail group)

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records to MB (mail box) records.

-o
Do not print output to standard out.
-p [server]
For use with -l. Query only the zone's primary nameserver (or server) for zone transfers, instead of those
authoritative servers that respond. Useful for testing unregistered zones.

-q
Quiet. Suppress warning, but not error, messages.
-r
Do not ask contacted server to query other servers, but require only the information that it has cached.
-t type
Look for type entries in the resource record. type may be A, NS, PTR, ANY, or * (all).
-u
Use TCP, not UDP.
-v
Verbose. Include all fields from resource record, even time-to-live and class, as well as "additional
information" and "authoritative nameservers" (provided by the remote nameserver).

-vv
Very verbose. Include information about host's defaults.
-w
Never give up on queried server.
-x
Allow multiple hosts or zones to be specified. If a server is also specified, the argument must be preceded
by -X.

-A
For hostnames, look up the associated IP address, and then reverse look up the hostname, to see if a
match occurs. For IP addresses, look up the associated hostname, and determine whether the host
recognizes that address as its own. For zones, check IP addresses for all hosts. Exit silently if no
incongruities are discovered.

-C
Similar to -l, but also check to see if the zone's name servers are really authoritative. The zone's SOA
(start of authority) records specify authoritative name servers (in NS fields). Those servers are queried; if
they do not have SOA records, host reports a lame delegation. Other checks are made as well.

-D
Similar to -H but include the names of hosts with more than one address per defined name.

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-E
Similar to -H but do not treat extra-zone hosts as errors. Extra-zone hosts are hosts in an undefined
subdomain.

-F file
Redirect standard out to file, and print extra resource record output only on standard out.
-G zone
Similar to -H but include the names of gateway hosts.
-H zone
Print the number of unique hosts within zone. Do not include aliases. Also list all errors found (extra-zone
names, duplicate hosts).

-I chars
Do not print warnings about domain names containing illegal characters chars, such as _.
-L level
For use with -l. List all delegated zones within this zone, up to level deep, recursively.
-P servers
For use with -l. servers should be a comma-separated list. Specify preferred hosts for secondary servers to
use when copying over zone data. Highest priority is given to those servers that match the most domain
components in a given part of servers.

-R
Treat non-fully-qualified hostnames as BIND does, searching each component of the local domain.
-S
For use with -l. Print all hosts within the zone to standard out. Do not print hosts within subzones. Include
class and IP address. Print warning messages (illegal names, lame delegations, missing records, etc.) to
standard error.

-T
Print time-to-live values (how long information about each host will remain cached before the
nameserver refreshes it).

-X server
Specify a server to query, and allow multiple hosts or zones to be specified.
-Z
When printing recource records, include trailing dot in domain names, and print time-to-live value and
class name.

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hostid hostid
Print the ID number in hexadecimal of the current host.

hostname hostname [option] [nameofhost]
Set or print name of current host system. A privileged user can set the hostname with the nameofhost argument.
Option
-a, --alias
Display the alias name of the host (if used).
-d, --domain
Print DNS domain name.
-f, --fqdn, --long
Print fully qualified domain name.
-F file, --file file
Consult file for hostname.
-h, --help
Print a help message and then exit.
-i, --ip-address
Display the IP address( es) of the host.
-s, --short
Trim domain information from the printed name.
-v, --verbose
Verbose mode.
-V, --version
Print version information and then exit.
-y, --yp, --nis
Display the NIS domain name. A privileged user can set a new NIS domain name with nameofhost.

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hwclock hwclock [options]
System administration command. Read or set the hardware clock. This command maintains change information
in /etc/ adjtime, which can be used to adjust the clock based on how much it drifts over time. hwclock replaces
the clock command. The single-letter options are included for compatibility with the older command.

Options
You may specify only one of the following options:
-a
Adjust the hardware clock based on information in /etc/ adjtime and set the system clock to the new time.
--adjust
Adjust the hardware clock based on information in /etc/ adjtime.
--date date
Meaningful only with the --set option. date is a string appropriate for use with the date command.
--debug
Print information about what hwclock is doing.
-r, --show
Print the current time stored in the hardware clock.
-s, --hctosys
Set the system time in accordance with the hardware clock.
--set
Set the hardware clock according to the time given in the --date parameter.
--test
Do not actually change anything. This is good for checking syntax.
-u, --utc
The hardware clock is stored in Universal Coordinated Time.
--version
Print version and exit.
-w, --systohc
Set the hardware clock in accordance with the system time.

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icmpinfo icmpinfo [options]
TCP/ IP command. Intercept and interpret ICMP packets. Print the address and name of the message's sender, the
source port, the destination port, the sequence, and the packet size. By default, provide information only about
packets that are behaving oddly.

Options
-k
Kill the syslogd process begun by -l.
-l
Record via syslogd. Only a privileged user may use this option.
-n
Use IP addresses instead of hostnames.
-p
Suppress decoding of port number: do not attempt to guess the name of the service that is listening at that
port.

-s
Include IP address of interface that received the packet, in case there are several interfaces on the host
machine.

-v
Verbose. Include information about normal ICMP packets. You may also specify -vv and -vvv for extra
verbosity.

id id [options] [username]
Display information about yourself or another user: user ID, group ID, effective user ID and group ID if
relevant, and additional group IDs.

Options
-g, --group
Print group ID only.
-G, --groups
Print supplementary groups only.
-n, --name
With -u, -g, or -G, print user or group name, not number.
-r, --real
With -u, -g, or -G, print real, not effective, user ID or group ID.
-u, --user

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Print user ID only.

--help
Print help message and then exit.
--version
Print version information.

identd in. identd [options] [kernelfile [kmemfile]]
TCP/ IP command. Provide the name of the user whose process is running a specified TCP/ IP connection. You
may specify the kernel and its memory space.

Options
-a ip_ address
Bind to ip_ address. Useful only with -b. By default, bind to the INADDR_ ANY address.
-b

Run standalone; not for use with inetd.
-d

Allow debugging requests.
-ggid

Attempt to run in the group gid. Useful only with -b.
-i

Run as a daemon, one process per request.
-l

Log via syslogd.
-m

Allow multiple requests per session.
-n

Return user IDs instead of usernames.
-N

Do not provide a user's name or user ID if the file .noident exists in the user's home directory.
-o

When queried for the type of operating system, always return OTHER.
-pport

Listen at port instead of the default, port 113.
-tseconds

Exit if no new requests have been received before seconds seconds have passed. Note that, with -i or -w,
the next new request will result in identd being restarted. Default is infinity (never exit).
-uuid

Attempt to run as uid. Useful only with -b.
-V

Print version and exit.
-w

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Run as a daemon, one process for all requests.

ifconfig ifconfig [interface]
ifconfig [interface address_ family parameters addresses]
TCP/ IP command. Assign an address to a network interface and/ or configure network interface parameters.
ifconfig is typically used at boot time to define the network address of each interface on a machine. It may be
used at a later time to redefine an interface's address or other parameters. Without arguments, ifconfig displays
the current configuration for a network interface. Used with a single interface argument, ifconfig displays that
particular interface's current configuration.

Arguments
interface
String of the form name unit, for example, en0.
address_ family
Since an interface may receive transmissions in differing protocols, each of which may require separate
naming schemes, you can specify the address_ family to change the interpretation of the remaining
parameters. You may specify inet (the default; for TCP/ IP), ax25 (AX. 25 Packet Radio), ddp (Appletalk
Phase 2), or ipx (Novell).

Parameters
The following parameters may be set with ifconfig:
allmulti/-allmulti
Enable/ disable sending of incoming frames to the kernel's network layer.
arp/-arp
Enable/ disable use of the Address Resolution Protocol in mapping between network-level
addresses and link-level addresses.

broadcast
(inet only.) Specify address to use to represent broadcasts to the network. Default is the address
with a host part of all 1s (i. e., x. y. z. 255 for a class C network).

debug/-debug
Enable/ disable driver-dependent debugging code.
dest_ address
Specify the address of the correspondent on the other end of a point-to-point link.
down
Mark an interface "down" (unresponsive).
hw class address
Set the interface's hardware class and address. class may be ether (Ethernet), ax25 (AX. 25 Packet
Radio), or ARCnet.

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irq addr
Set the device's interrupt line.
metric n
Set routing metric of the interface to n. Default is 0.
mtu num
Set the interface's Maximum Transfer Unit (MTU).
multicast
Set the multicast flag.
netmask mask
(inet only.) Specify how much of the address to reserve for subdividing networks into
subnetworks. mask can be specified as a single hexadecimal number with a leading 0x, with a dot
notation Internet address, or with a pseudonetwork name listed in the network table /etc/ networks.

pointopoint/-pointopoint [address]
Enable/ disable point-to-point interfacing, so that the connection between the two machines is
dedicated.

up
Mark an interface "up" (ready to send and receive).
trailers/-trailers
Request/ disable use of a "trailer" link-level encapsulation when sending.
address
Either a hostname present in the hostname database (/ etc/ hosts), or an Internet address expressed in the
Internet standard dot notation.

imake imake options
C preprocessor (cpp) interface to the make utility. imake (for include make) solves the portability problem of
make by allowing machine dependencies to be kept in a central set of configuration files, separate from the
descriptions of the various items to be built. The targets are contained in the Imakefile, a machine-independent
description of the targets to be built, written as cpp macros. imake uses cpp to process the configuration files
and the Imakefile, and to generate machine-specific Makefiles, which can then be used by make.

One of the configuration files is a template file, a master file for imake. This template file (default is
Imake. tmpl) #includes the other configuration files that contain machine dependencies such as variable
assignments, site definitions, and cpp macros, and directs the order in which the files are processed. Each file
affects the interpretation of later files and sections of Imake. tmpl. Comments may be included in imake
configuration files, but the initial # needs to be preceded with an empty C comment:

/**/#For more information, see cpp and make. Also check out the Nutshell Handbook Software Portability with
imake, by Paul DuBois.

Options

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-Ddefine
Set directory-specific variables. This option is passed directly to cpp.
-e
Execute the generated Makefile. Default is to leave this to the user.
-f filename
Name of per-directory input file. Default is Imakefile.
-Idirectory
Directory in which imake template and configuration files may be found. This option is passed directly to
cpp.

-s filename
Name of make description file to be generated. If filename is a --, the output is written to stdout. The
default is to generate, but not execute, a Makefile.

-Ttemplate
Name of master template file used by cpp. This file is usually located in the directory specified with the -I
option. The default file is Imake. tmpl.

-v
Print the cpp command line used to generate the Makefile.
Tools
Following is a list of tools used with imake:
makedepend [options] files
Create header file dependencies in Makefiles. make-depend reads the named input source files in
sequence and parses them to process #include, #define, #undef, #ifdef, #ifndef, #endif, #if, and #else
directives so it can tell which #include directives would be used in a compilation. makedepend
determines the dependencies and writes them to the Makefile. make then knows which object files must
be recompiled when a dependency has changed. makedepend has the following options:

--options --
Ignore any unrecognized options following a double hyphen. A second double hyphen terminates
this action. Recognized options between the hyphens are processed normally.

-a
Append dependencies to any existing ones instead of replacing existing ones.
-ffilename
Write dependencies to filename instead of to Makefile.
-m
Print a warning when encountering a multiple inclusion.
-sstring
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Use string as delimiter in file, instead of # DO NOT DELETE THIS LINE --make depend
depends on it.

-v
Verbose. List all files included by main source file.
-Dname
Define name with the given value (first form) or with value 1 (second form).
-Idir
Add directory dir to the list of directories searched.
-Ydir
Search only dir for include files. Ignore standard include directories.
mkdirhier dir...
Create directory dir and all missing parent directories during file installation operations.
xmkmf [option] [topdir] [curdir]
Bootstrap a Makefile from an Imakefile. topdir specifies the location of the project root directory. curdir
(usually omitted) is specified as a relative pathname from the top of the build tree to the current directory.
The -a option is equivalent to the following command sequence:

% xmkmf% make Makefiles% make includes% make depend

Configuration files
Following is a list of the imake configuration files:
Imake. tmpl
Master template for imake. Imake. tmpl includes all the other configuration files, plus the Imakefile in the
current directory.

Imake. params
Contains definitions that apply across sites and vendors.
Imake. rules
Contains cpp macro definitions that are configured for the current platform. The macro definitions are fed
into imake, which runs cpp to process the macros. Newlines (line continuations) are indicated by the
string @@\ (double at sign, backslash).

site. def
Contains site-specific (as opposed to vendor-specific) information, such as installation directories, what
set of programs to build, and any special versions of programs to use during the build. The site. def file
changes from machine to machine.

Project. tmpl

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File containing X-specific variables.
Library. tmpl
File containing library rules.
Server. tmpl
File containing server-specific rules.
.cf
The .cf files are the vendor-specific VendorFiles that live in Imake. vb. A .cf file contains platform-specific
definitions, such as version numbers of the operating system and the compiler and workarounds
for missing commands. The definitions in .cf files override the defaults, defined in Imake. params.

The Imakefile
The Imakefile is a per-directory file that indicates targets to be built and installed and rules to be applied. imake
reads the Imakefile and expands the rules into Makefile target entries. An Imakefile may also include definitions
of make variables and list the dependencies of the targets. The dependencies are expressed as cpp macros,
defined in Imake. rules. Whenever you change an Imakefile, you need to rebuild the Makefile and regenerate
header file dependencies. For more information on imake, see Software Portability with imake by Paul DuBois.

imapd imapd
TCP/ IP command. The Interactive Mail Access Protocol (IMAP) server daemon. imapd is invoked by inetd and
listens on port 143 for requests from IMAP clients. IMAP allows mail programs to access remote mailboxes as if
they were local. IMAP is a richer protocol than POP because it allows a client to retrieve message-level
information from a server mailbox instead of the entire mailbox. IMAP can be used for online and offline
reading. The popular Pine mail client contains support for IMAP.

inetd inetd [option] [configuration_ file]
TCP/ IP command. Internet services daemon. inetd listens on multiple ports for incoming connection requests.
When it receives one, it spawns the appropriate server. When started, inetd reads its configuration information
from either configuration_ file, or from the default configuration file /etc/ inetd. conf. It then issues a call to
getservbyname, creates a socket for each server, and binds each socket to the port for that server. It does a listen
on all connection-based sockets, then waits, using select for a connection or datagram.

When a connection request is received on a listening socket, inetd does an accept, creating a new socket. It then
forks, dups, and execs the appropriate server. The invoked server has I/ O to stdin, stdout, and stderr done to the
new socket, connecting the server to the client process.

When there is data waiting on a datagram socket, inetd forks, dups, and execs the appropriate server, passing it
any server program arguments. A datagram server has I/ O to stdin, stdout, and stderr done to the original
socket. If the datagram socket is marked as wait, the invoked server must process the message before inetd
considers the socket available for new connections. If the socket is marked nowait, inetd continues to process
incoming messages on that port.

The following servers may be started by inetd: bootpd, bootpgw, fingerd, ftpd, imapd, popd, rexecd, rlogind,
rshd, talkd, telnetd, and tftpd. Do not arrange for inetd to start named, routed, rwhod, sendmail, listen, or
any NFS server.

inetd rereads its configuration file when it receives a hangup signal, SIGHUP. Services may be added, deleted,
or modified when the configuration file is reread.

Option
-d

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Turn on socket-level debugging and print debugging information to stdout.
Files
/etc/ inetd. conf
Default configuration file.
/var/ run/ inetd. pid
inetd's process ID.

info info [options] [topics]
GNU hypertext reader: display online documentation previously built from Texinfo input. Info files are arranged
in a hierarchy and can contain menus for subtopics. When entered without options, the command displays the
top-level info file (usually /usr/ local/ info/ dir). When topics are specified, find a subtopic by choosing the first
topic from the menu in the top-level info file, the next topic from the new menu specified by the first topic, and
so on. The initial display can also be controlled by the -f and -n options.

Options
-d directories, --directory directories
Search directories, a colon-separated list, for info files. If this option is not specified, use the INFOPATH
environment variable or the default directory (usually /usr/ local/ info).

--dribble file
Store each keystroke in file, which can be used in a future session with the --restore option to return to
this place in info.

-f file, --file file
Display specified info file.
-n node, --node node
Display specified node in the info file.
-o file, --output file
Copy output to file instead of displaying it at the screen.
--help
Display brief help.
--restore file
When starting, execute keystrokes in file.
--subnodes
Display subtopics.
--version
Display version.

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--vi-keys
Use vi-like key bindings.

init init [option] [runlevel]
System administration command.
Option
-t seconds
When changing runlevels, send SIGKILL seconds after SIGTERM. Default is 20.
Files
init is the first process run by any Unix machine at boot time. It verifies the integrity of all filesystems and then
creates other processes, using fork and exec, as specified by /etc/ inittab. Which processes may be run are
controlled by runlevel. All process terminations are recorded in /var/ run/ utmp and /var/ log/ wtmp. When the
runlevel changes, init sends SIGTERM and then, after 20 seconds, SIGKILL to all processes that cannot be run
in the new runlevel.

Runlevels
The current runlevel may be changed by telinit, which is often just a link to init. The default runlevels vary from
distribution to distribution, but these are standard:

0
Halt the system.
1, s, S
Single-user mode.
6
Reboot the system.
q, Q
Reread /etc/ inittab.
Check the /etc/ inittab file for runlevels on your system.

insmod insmod [options] file [symbol= value ...]
System administration command. Load the module file into the kernel, changing any symbols that are defined on
the command line. If the module file is named file. o or file. mod, the module will be named file.

Options
-f
Force loading of module, even if some problems are encountered.
-m
Output a load map.

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-o name
Name module name instead of attempting to name it from the object file's name.
-x
Do not export: do not add any external symbols from the module to the kernel's symbol table.

install install [options] [file] directories
System administration command. Used primarily in makefiles to update files. install copies files into user-specified
directories. It will not overwrite a file. Similar to cp but attempts to set permission modes, owner, and
group.

Options
-d, --directory
Create any missing directories.
-g group, --group group
Set group ID of new file to group (privileged users only).
-m mode, --mode mode
Set permissions of new file to mode (octal or symbolic). By default, the mode is 0755.
-o [owner], --owner [owner]
Set ownership to owner or, if unspecified, to root (privileged users only).
-s, --strip
Strip symbol tables.

ipchains ipchains command [options]
System administration command. Edit IP firewall rules in the 2.2 Linux kernel. A 2.2 Linux kernel compiled
with firewall support will examine the headers of all network packets and compare them to matching rules to see
what it should do with the packet. A firewall rule consists of some matching criteria and a target, a result to be
applied if the packet matches the criteria. The rules are organized into chains. You can use these rules to build a
firewall or just reject certain kinds of network connections.

Firewall rules are organized into chains, an ordered checklist that the kernel works through looking for matches.
There are three built-in chains input, output, and forward. Packets entering the system are tested against the
input chain. Those exiting the system are checked against the output chain. If an incoming packet is destined
for some other system, it is checked against the forward chain. Each of these chains has a default target, a
policy, in case no match is found. User-defined chains can be created and used as targets for packets, but they
have no default policies. If no match can be found in a user-defined chain, the packet is returned to the chain
from which it was called and tested against the next rule in that chain.

ipchains only changes the rules in the running kernel. When the system is powered off, all those changes are
lost. You can use the ipchains-save command to make a script you can later run with ipchains-restore to restore
your firewall settings. Such a script is often called at boot up and many distributions have an ipchains
initialization script that uses the output from ipchains-save.

Commands

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ipchains is always invoked with one of the following commands:

-A chain rules, --append chain rules
Append new rules to chain.
-I chain number rules, --insert <chain number rules
Insert rules into chain at the ordinal position given by number.
-D chain rules, --delete chain rules
Delete rules from chain. Rules can be specified by their ordinal number in the chain as well as by a
general rule description.

-R chain number rule, --replace chain number rule
Replace a rule in chain. The rule to be replaced is specified by its ordinal number.
-C chain rule, --check chain rules
Construct a network packet that matches the given rule and check how chain will handle it. The rule must
describe the source, destination, protocol, and interface of the packet to be constructed.

-L [chain], --list $PARAMETER
List the rules in chain. If no chain is specified, list the rules in all chains.
-ML, --masquerading --list
List masquerading connections.
-MS tcp tcpfin udp, --masquerading --set tcp tcpfin udp
Set timeout value in seconds for masquerading connections. -MS always takes three parameters
specifying the timeout values for TCP sessions, TCP sessions that have received a FIN packet, and UDP
packets.

-F chain, --flush chain
Remove all rules from chain.
-Z [chain], --zero [chain]
Reset the packet and byte counters in chain. If no chain is specified, all chains will be reset. When used
without specifying a chain and combined with the -L command, it lists the current counter values before
they are reset.

-N chain, --new-chain chain
Create a new chain. The chain's name must be unique.
-X [chain], --delete-chain chain
Delete chain. Only user-defined chains can be deleted, and there can be no references to the chain to be
deleted. If no argument is given, all user-defined chains will be deleted.

-P chain target, --policy chain target
Set the policy for a built-in chain; the target itself cannot be a chain.

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-h [icmp]

Print a brief help message. If the option icmp is given, print a list of valid ICMP types.
Targets
A target can be the name of a chain or one of the following special values:
ACCEPT
Let the packet through.
DENY
Drop the packet.
MASQ
Masquerade the packet so it appears that it originated from the current system. Reverse packets from
masqueraded connections are unmasqueraded automatically. This is a legal target for only the forward
chain, or user-defined chains used in forwarding packets. To use this target, the kernel must be compiled
with support for IP masquerading.

REDIRECT [port]
Redirect incoming packets to a local port on which you are running a transparent proxy program. If the
specified port is 0 or is not given, the destination port of the packet is used as the redirection port.
REDIRECT is only a legal target for the input chain or user-defined chains used in handling incoming
packets. The kernel must be compiled with support for transparent proxies.

REJECT
Drop the packet and send an ICMP message back to the sender indicating the packet was dropped.
RETURN
Return to the chain from which this chain was called and check the next rule. If RETURN is the target of
a rule in a built-in chain, then the built-in chain's default policy is applied.

Rule specification parameters
These options are used to create rules for use with the preceding commands. Rules consist of some matching
criteria and usually a target to jump to (-j) if the match is made. Many of the parameters for these matching rules
can be expressed as a negative with an exclamation point (!) meaning "not." Those rules will match everything
except the given parameter.

-s [!] address[/ mask] [!] [port], --source [!] address[/ mask] [!] [port]
Specifies the source address and port of the packet that will match this rule. The address may be supplied
as a hostname, a network name, or an IP address. The optional mask is the netmask to use and may be
supplied either in the traditional form (e. g., /255.255.255.0) or in the modern form (e. g., /24). The
optional port specifies the TCP, UDP, or ICMP type that will match. You may supply a port specification
only if you've supplied the -p parameter with one of the tcp, udp or icmp protocols. A colon can be used
to indicate an inclusive range of ports or ICMP values to be used. (e. g., 20: 25 for ports 20 through 25). If
the first port parameter is missing, the default value is 0. If the second is omitted, the default value is
65535.

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-d [!] address[/ mask] [!] [port], --destination [!] address[/ mask] [port]
Match packets with the destination address. The syntax for this command's parameters is the same as for
the -s option.

-j target, --jump target
Jump to a special target or a user-defined chain. If this option is not specified for a rule, matching the rule
only increases the rule's counters and the packet is tested against the next rule.

-i [!] name, --interface name
Match packets from interface name[+]. name is the network interface used by your system (e. g., eth0 or
ppp0). A + can be used as a wildcard, so ppp+ would match any interface name beginning with ppp.

[!] -f, [!]--fragment $PARAMETER
The rule applies to everything but the first fragment of a fragmented packet.
--source-port [!] port
Match packets from the source port. The syntax for specifying ports can be found in the preceding
description of the -s option.

--destination-port [!] port
Match packets with the destination port. The syntax for specifying ports can be found in the preceding
description of the -s option.

--icmp-type [!] type
Match packets with ICMP type name or number of type.
Options
-b, --bidirectional
Put rule in both the input and output chain so packets will be matched in both directions.
-v, --verbose
Verbose mode.
-n, --numeric
Print all IP address and port numbers in numeric form. By default, names are displayed when possible.
-l, --log
Log information for the matching packet to the system log.
-t andmask xormask, --TOS andmask xormask
Change the Type of Service field in the packet's header. The TOS field is first ANDed with the 8-bit
hexadecimal mask andmask, then XORed with the 8-bit hexadecimal mask xormask. Rules that would
affect the least significant bit (LSB) portion of the TOS field are rejected.

-x, --exact
Expand all numbers in a listing (-L). Display the exact value of the packet and byte counters instead of

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rounded figures.

[!] -y, --syn
Match only incoming TCP connection requests, those with the SYN bit set and the ACK and FIN bits
cleared. This blocks incoming TCP connections but leaves outgoing connections unaffected.

--line-numbers
Used with the -L command. Add the line number to the beginning of each rule in a listing indicating its
position in the chain.

--no-warnings
Disable all warnings

ipchains-restore ipchains-restore [options]
System administration command. Restore firewall rules. ipchains-restore takes commands generated by
ipchains-save and uses them to restore the firewall rules for each chain. Often used by initialization scripts to
restore firewall settings on boot.

Options
-f
Force updates of existing chains without asking.
-v
Print rules as they are being restored.
-p
If a nonexisting chain is targeted by a rule, create it.

ipchains-save ipchains-save [chain] [option]
System administration command. Print the IP firewall rules currently stored in the kernel to stdout. If no chain
is given, all chains will be printed. Output is usually redirected to a file, which can later be used by ipchains-restore
to restore the firewall.

Option
-v
Print out rules to stderr as well as stdout, making them easier to see when redirecting output.

ipfwadm ipfwadm category command parameters [options]
ipfwadm -M [ -l | -s ] [options]
Administer a firewall and its rules, firewall accounting, and IP masquerading in the 2.0 Linux kernel. This
command is replaced with ipchains in the 2.2 kernel, and ipchains is replaced by iptables in the 2.4 kernel.

There are four categories of rules: IP packet accounting, IP input firewall, IP output firewall, and IP forwarding
firewall. The rules are maintained in lists, with a separate list for each category. See the manpage for ipfw( 4) for
a more detailed description of how the lists work.

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Each ipfwadm command specifies only one category and one rule. To create a secure firewall, you issue
multiple ipfwadm commands; the combination of their rules work together to ensure that your firewall operates
as you intend it to. The second form of the command is for masquerading. The commands -l and -s described in
the later list are the only ones that can be used with the masquerading category, -M.

Categories
One of the following flags is required to indicate the category of rules to which the command that follows the
category applies.

-A [direction]
IP accounting rules. Optionally, a direction can be specified:
in
Count only incoming packets.
out
Count only outgoing packets.
both
Count both incoming and outgoing packets; this is the default.
-F
IP forwarding firewall rules.
-I
IP input firewall rules.
-M
IP masquerading administration. Can be used only with the -l or -s command.
-O
IP output firewall rules.
Commands
The category is followed by a command indicating the specific action to be taken. Unless otherwise specified,
only one action can be given on a command line. For the commands that can include a policy, the valid policies
are:

accept
Allow matching packets to be received, sent, or forwarded.
deny
Block matching packets from being received, sent, or forwarded.
reject
Block matching packets from being received, sent, or forwarded and also return an ICMP error message
to the sending host.

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The commands are:

-a [policy]
Append one or more rules to the end of the rules for the category. No policy is specified for accounting
rules. For firewall rules, a policy is required. When the source and/ or destination names resolve to more
than one address, a rule is added for each possible address combination.

-c
Check whether this IP packet would be accepted, denied, or rejected by the type of firewall represented
by this category. Valid only when the category is -I, -O, or -F. Requires the -V parameter to be specified
(see "Parameters," later).

-d [policy]
Delete one or more entries from the list of rules for the category. No policy is specified for accounting
rules. The parameters specified with this command must exactly match the parameters from an append or
insert command, or no match will be found and the rule will not be removed. Only the first matching rule
in the list of rules is deleted.

-f
Remove (flush) all rules for the category.
-h
Display a help message with a brief description of the command syntax. Specified with no category:
% ipfwadm -h-i [policy]
Insert a new rule at the beginning of the selected list for the category. No policy is specified for
accounting rules. For firewall rules, a policy is required. When the source and/ or destination names
resolve to more than one address, a rule is added for each possible address combination.

-l
List all rules for the category. This option may be combined with the -z option to reset the packet and
byte counters after listing their current values. Unless the -x option is also specified, the packet and byte
counters are shown as numberK or numberM, rounded to the nearest integer. See also the -e option
described under "Options" later.

-p policy
Change the default policy for the selected type of firewall to policy. The default policy is used when no
matching rule is found. Valid only with -I, -O, or -F.

-s tcp tcpfin udp
Set the masquerading timeout values; valid only with -M. The three parameters are required and represent
the timeout value in seconds for TCP sessions, TCP sessions after receiving a FIN packet, and UDP
packets, respectively. A timeout value of 0 preserves the current timeout value of the corresponding
entry.

-z
Reset the packet and byte counters for all rules in the category. This command may be combined with the
-l command.

Parameters
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The following parameters can be specified with the -a, -i, -d, or -c commands, except as noted. Multiple
parameters can be specified on a single ipfwadm command line.

-D address[/ mask] [port ...]
The destination specification (optional). See the description of -S for the syntax, default values, and other
requirements. ICMP types cannot be specified with -D.

-P protocol
The protocol of the rule or packet; possible values are tcp, udp, icmp, or all. Defaults to all, which
matches all protocols. -P cannot be specified with the -c command.

-S address[/ mask] [port ...]
The source IP address, specified as a hostname, a network name, or an IP address. The source address and
mask default to 0.0.0.0/ 0. If -S is specified, -P must also be specified. The optional mask is specified as a
network mask or as the number of 1s on the left of the network mask (e. g., a mask of 24 is equivalent to
255.255.255.0). The mask defaults to 32. One or more values of port may optionally be specified,
indicating what ports or ICMP types the rule applies to. The default is all. Ports may be specified by their
/etc/ services entry. The syntax for indicating a range of ports is:

lowport: highportFor example:
-S 172.29.16.1/ 24 ftp: ftp-data-V address
The address of the network interface the packet is received from (if category is -I) or is being sent to (if
category is -O). address can be a hostname or an IP address, and defaults to 0.0.0.0, which matches any
interface address. -V is required with the -c command:

-V 172.29.16.1-W name
Identical to -V but takes a device name instead of its address:
-W ppp0Options
-b
Bidirectional mode. The rule matches IP packets in both directions. This option is valid only with the -a, -i,
and -d commands.

-e
Extended output. Used with the -l command to also show the interface address and any rule options.
When listing firewall rules, also shows the packet and byte counters and the TOS (Type of Service)
masks. When used with -M, also shows information related to delta sequence numbers.

-k
Match TCP acknowledgment packets (i. e., only TCP packets with the ACK bit set). This option is
ignored for all other protocols and is valid only with the -a, -i, and -d commands.

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-m

Accept masquerade packets for forwarding, making them appear to have originated from the local host.
Recognizes reverse packets and automatically demasquerades them, bypassing the forwarding firewall.
This option is valid only in forwarding firewall rules with policy accept. The kernel must have been
compiled with CONFIG_ IP_ MASQUERADE defined.

-n
Numeric output. Print IP addresses and port numbers in numeric format.
-o
Log packets that match this rule to the kernel log. This option is valid only with the -a, -i, and -d
commands. The kernel must have been compiled with CONFIG_ IP_ FIREWALL_ VERBOSE defined.

-r [port]
Redirect packets to a local socket, even if they were sent to a remote host. If port is 0 (the default), the
packet's destination port is used. This option is valid only in input firewall rules with policy accept. The
kernel must have been compiled with CONFIG_ IP_ TRANSPARENT_ PROXY defined.

-t andmask xormask
Specify masks used for modifying the TOS field in the IP header. When a packet is accepted (with or
without masquerading) by a firewall rule, its TOS field is bitwise ANDed with andmask, and the result is
bitwise XORed with xormask. The masks are specified as 8-bit hexadecimal values. This option is valid
only with the -a, -i, and -d commands and has no effect when used with accounting rules or with firewall
rules for rejecting or denying a packet.

-v
Verbose output. Print detailed information about the rule or packet to be added, deleted, or checked. This
option is valid only with the -a, -i, -d, and -c commands.

-x
Expand numbers. Display the exact value of the packet and byte counters, instead of a rounded value.
This option is valid only when the counters are being listed anyway (see also the -e option).

-y
Match TCP packets with the SYN bit set and the ACK bit cleared. This option is ignored for packets of
other protocols and is valid only with the -a, -i, and -d commands.

iptables iptables command [options]
System administration command. Configure netfilter filtering rules. In the 2.4 kernel, the ipchains firewall
capabilities are replaced with the netfilter kernel module. netfilter can be configured to work just like ipchains,
but it also comes with the module iptables, which is similar to ipchains but extensible. iptables rules consist of
some matching criteria and a target, a result to be applied if the packet matches the criteria. The rules are
organized into chains. You can use these rules to build a firewall, masquerade your local area network, or just
reject certain kinds of network connections.

There are three built-in tables for iptables, one for network filtering (filter), one for Network Address
Translation (nat), and the last for specialized packet alterations (mangle). Firewall rules are organized into
chains, ordered check lists of rules that the kernel works through looking for matches. The filter table has three
built-in chains: INPUT, OUTPUT, and FORWARD. The INPUT and OUTPUT chains handle packets
originating from or destined for the host system. The FORWARD chain handles mail just passing through the
host system. The nat table also has three built-in chains: PREROUTING, POSTROUTING, and OUTPUT.
mangle has only two chains: PREROUTING and OUTPUT.

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netfilter checks packets entering the system. After applying any PREROUTING rules it passes them to the
INPUT chain or to the FORWARD chain if the packet is just passing through. Upon leaving, the system
packets are passed to the OUTPUT chain and then on to any POSTROUTING rules. Each of these chains has a
default target, a policy, in case no match is found. User-defined chains can also be created and used as targets for
packets but do not have default policies. If no match can be found in a user-defined chain, the packet is returned
to the chain from which it was called and tested against the next rule in that chain.

iptables only changes the rules in the running kernel. When the system is powered off, all changes are lost. You
can use the iptables-save command to make a script you can run with iptables-restore to restore your firewall
settings. Such a script is often called at bootup. Many distributions will have an iptables initialization script that
uses the output from iptables-save.

Commands
iptables is always invoked with one of the following commands:
-A chain rules, --append chain rules
Append new rules to chain.
-I chain number rules, --insert chain number rules
Insert rules into chain at the ordinal position given by number.
-D chain rules, --delete chain rules
Delete rules from chain. Rules can be specified by their ordinal number in the chain as well as by a
general rule description.

-R chain number rule, --replace chain number rule
Replace a rule in chain. The rule to be replaced is specified by its ordinal number.
-C chain rule, --check chain rules
Check how chain will handle a network packet that matches the given rule. The rule must describe the
source, destination, protocol, and interface of the packet to be constructed.

-L [chain], --list $PARAMETER
List the rules in chain or all chains if chain is not specified.
-F [chain], --flush chain
Remove all rules from chain or from all chains if chain is not specified.
-Z [chain], --zero chain
Zero the packet and byte counters in chain. If no chain is specified, all chains will be reset. When used
without specifying a chain and combined with the -L command, it lists the current counter values before
they are reset chain.

-N chain, --new-chain chain
Create a new chain. The chain's name must be unique. This is how user-defined chains are created.
-X [chain], --delete-chain chain
Delete the specified user-defined chain or all user-defined chains if no chain is specified.
-P chain target, --policy chain target

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Set the default policy for a built-in chain; the target itself cannot be a chain.
-E old-chain new-chain, --rename-chain old-chain new-chain
Rename old-chain to new-chain.
-h [icmp]
Print a brief help message. If the option icmp is given, print a list of valid ICMP types.
Targets
A target may be the name of a chain or one of the following special values.
ACCEPT
Let the packet through.
DROP
Drop the packet.
QUEUE
Send packets to the user space for processing.
RETURN
Stop traversing the current chain and return to the point in the previous chain from which this one was
called. If RETURN is the target of a rule in a built-in chain, the built-in chain's default policy is applied.

-p [!] name, --protocol [!]$ PARAMETER
Match packets of protocol name. The value of name can be given as a name or number as found in the
file /etc/ protocols. The most common values are tcp, udp, icmp, or the special value all. The number 0 is
equivalent to all and this is the default value when this option is not used. If there are extended matching
rules associated with the specified protocol, they will be loaded automatically. You need not use the -m
option to load them.

-s [!] address[/ mask] [!] [port], --source [!] address[/ mask] [!] [port]
Match packets with the source address. The address may be supplied as a hostname, a network name, or
an IP address. The optional mask is the netmask to use and may be supplied either in the traditional form
(e. g., /255.255.255.0) or in the modern form (e. g., /24).

-d [!] address[/ mask] [!] [port], --destination [!] address[/ mask] [port]
Match packets from the destination address. See the description of -s for the syntax of this option.
-j target, --jump target
Jump to a special target or a user-defined chain. If this option is not specified for a rule, matching the rule
only increases the rule's counters, and the packet is tested against the next rule.

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-i [!] name[+], --in-interface name[+]
Match packets being received from interface name. name is the network interface used by your system
(e. g., eth0 or ppp0). A + can be used as a wildcard, so ppp+ would match any interface name beginning
with ppp

-o [!] name[+], --out-interface name[+]
Match packets being sent from interface name. See the description of -i for the syntax for name.
[!] -f, [!]--fragment $PARAMETER
The rule applies only to the second or further fragments of a fragmented packet.
Options
-v, --verbose
Verbose mode.
-n, --numeric
Print all IP address and port numbers in numeric form. By default, text names are displayed when
possible.

-x, --exact
Expand all numbers in a listing (-L). Display the exact value of the packet and byte counters instead of
rounded figures.

-m module, --match
Explicitly load matching rule extensions associated with module. See the following section, "Match
Extensions."

-h [icmp], --help [icmp]
Print help message. If icmp is specified, a list of valid ICMP type names will be printed. -h can also be
used with the -m option to get help on an extension module.

--line-numbers
Used with the -L command. Add the line number to the beginning of each rule in a listing, indicating its
position in the chain.

Match extensions
Several kernel modules come with netfilter to extend matching capabilities of rules. Those associated with
particular protocols are loaded automatically when the -p option is used to specify the protocol. Others need to
be loaded explicitly with the -m option.

tcp
Loaded when -p tcp is the only protocol specified.
--source-port [!] [port][: port], --sport [!] [port][: port]
Match the specified source ports. Using the colon specifies an inclusive range of services to
match. If the first port is omitted, 0 is the default. If the second port is omitted, 65535 is the
default. You can also use a dash instead of a colon to specify the range.

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--destination-port [!] [port][: port], --dport [!] [port][: port]

Match the specified destination ports. The syntax is the same as for --source-port.
--tcp-flags [!] mask comp
Match the packets with the TCP flags specified by mask and comp. mask is a comma-separated list
of flags that should be examined. comp is a comma-separated list of flags that must be set for the
rule to match. Valid flags are SYN, ACK, FIN, RST, URG, PSH, ALL, and NONE.

[!] --syn
Match packets with the SYN bit set and the ACK and FIN bits cleared. These are packets that
request TCP connections; blocking them prevents incoming connections. Shorthand for --tcp-flags
SYN, RST, ACK SYN.

udp
Loaded when -p udp is the only protocol specified.
--source-port [!] [port][: port], --sport [!] [port][: port]
Match the specified source ports. The syntax is the same as for the --source-port option of the
TCP extension.

--destination-port [!] [port][: port], --dport [!] [port][: port]
Match the specified destination ports. The syntax is the same as for --source-port option of the
TCP extension.

icmp
Loaded when -p icmp is the only protocol specified.
--icmp-type [!] type
Match the specified icmp type. type may be a numeric ICMP type or one of the ICMP type names
shown by the command iptables -p icmp -h.

mac
Loaded explicitly with the -m option.
--mac-source [!] address
Match the source address that transmitted the packet. address must be given in colon-separated
hexbyte notation (for example, --mac-source 00: 60: 08: 91: CC: B7.

limit
Loaded explicitly with the -m option. The limit extensions are used to limit the number of packets
matched. This is useful when combined with the LOG target. Rules using this extension match until the
specified limit is reached.

--limit rate
Match addresses at the given rate. rate is specified as a number with an optional /second, /minute,
hour, or /day suffix. When this option is not set, the default is '3/ hour'.

--limit-burst [number]

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Set the maximum number of packets to match in a burst. Once the number has been reached, no
more packets are matched for this rule until the number has recharged. It recharges at the rate set
by the --limit option. When not specified, the default is 5.

multiport
Loaded explicitly with the -m option. The multiport extensions match sets of source or destination ports.
These rules can be used only in conjunction with -p tcp and -p udp. Up to 15 ports can be specified in a
comma-separated list.

--source-port [ports]
Match the given source ports.
--destination-port [ports]
Match the given destination ports.
--port [ports]
Match if the packet has the same source and destination port and that port is one of the given
ports.

mark
Loaded explicitly with the -m option. This module works with the MARK extension target:
--mark value[/ mask]
Match the given unsigned mark value. If a mask is specified, it is logically ANDed with the mark
before comparison.

owner
Loaded explicitly with the -m option. The owner extensions match a local packet's creator's user, group
process, and session IDs. This makes sense only as a part of the OUTPUT chain.

--uid-owner userid
Match packets created by a process owned by userid.
--gid-owner groupid
Match packets created by a process owned by groupid.
--pid-owner processid
Match packets created by process ID processid.
--sid-owner sessionid
Match packets created by a process in the session sessionid.
state
Loaded explicitly with the -m option. This module matches the connection state of a packet.
--state states
Match the packet if it has one of the states in the comma-separated list states. Valid states are
INVALID, ESTABLISHED, NEW, and RELATED.

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tos
Loaded explicitly with the -m option. This module matches the Type of Service field in a packet's header.
--tos value
Match the packet if it has a TOS of value. value can be a numeric value or a Type of Service
name. iptables -m tos -h will give you a list of valid TOS values.

Target extensions
Extension targets are optional additional targets supported by separate kernel modules. They have their own
associated options.

LOG
Log the packet's information in the system log.
--log-level level
Set the syslog level by name or number (as defined by syslog. conf).
--log-prefix prefix
Begin each log entry with the string prefix. The prefix string may be up to 30 characters long.
--log-tcp-sequence
Log the TCP sequence numbers. This is a security risk if your log is readable by users.
--log-tcp-options
Log options from the TCP packet header.
--log-ip-options
Log options from the IP packet header.
MARK
Used to mark packets with an unsigned integer value you can use later with the mark matching
extension. Valid only with the mangle table.

--set-mark value
Mark the packet with value.
REJECT
Drop the packet and, if appropriate, send an ICMP message back to the sender indicating the packet was
dropped. If the packet was an ICMP error message, an unknown ICMP type, or a nonhead fragment, or if
too many ICMP messages have already been sent to this address, no message is sent.

--reject-with type
Send the specified ICMP message type. Valid values are icmp-net-unreachable, icmp-host-
unreachable, icmp-port-unreachable, or icmp-proto-unreachable. If the packet was an ICMP
ping packet, type may also be echo-reply.

TOS

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Set the Type of Service field in the IP header. TOS is a valid target only for rules in the mangle table.
--set-tos value
Set the TOS field to value. You can specify this as an 8-bit value or as a TOS name. You can get a
list of valid names using iptables -j TOS -h.

SNAT
Modify the source address of the packet and all future packets in the current connection. SNAT is valid
only as a part of the POSTROUTING chain in the nat table.

--to-source address[-address][ port-port]
Specify the new source address or range of addresses. If a tcp or udp protocol has been specified
with the -p option, source ports may also be specified. If none is specified, map the new source to
the same port if possible. If not, map ports below 512 to other ports below 512, those between 512
and 1024 to other ports below 1024, and ports above 1024 to other ports above 1024.

DNAT
Modify the destination address of the packet and all future packets in the current connection. DNAT is
valid only as a part of the POSTROUTING chain in the nat table.

--to-destination address[-address][ port-port]
Specify the new destination address or range of addresses. The arguments for this option are the
same as the --to-source argument for the SNAT extension target.

MASQUERADE
Masquerade the packet so it appears that it originated from the current system. Reverse packets from
masqueraded connections are unmasqueraded automatically. This is a legal target only for chains in the
nat table that handle incoming packets and should be used only with dynamic IP addresses (like dial-up.)
For static addresses use DNAT.

--to-ports port[-port]
Specify the port or range of ports to use when masquerading. This option is only valid if a tcp or
udp protocol has been specified with the -p option. If this option is not used, the masqueraded
packet's port will not be changed.

REDIRECT [--to-port port]
Redirect the packet to a local port. This is useful for creating transparent proxies.
--to-ports port[-port]
Specify the port or range of ports on the local system to which the packet should be redirected.
This option is valid only if a tcp or udp protocol has been specified with the -p option. If this
option is not used, the redirected packet's port will not be changed.

iptables-restore iptables-restore [file]
System administration command. Restore firewall rules. iptables-restore takes commands generated by iptables-save
and uses them to restore the firewall rules for each chain. Often used by initialization scripts to restore
firewall settings on boot. file is the name of a file whose contents were generated by iptables-save. If not
specified, the command takes its input from stdin. This command was not completed at the time this book went
to print. There may be options not listed here.

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iptables-save iptables-save [chain]
System administration command. Print the IP firewall rules currently stored in the kernel to stdout. If no chain is
given, all chains will be printed. Output may be redirected to a file that can later be used by iptables-restore to
restore the firewall. This command was not completed at the time this book went to print. There may be options
not listed here.

ispell ispell [options] [files]
Compare the words of one or more named files with the system dictionary. Display unrecognized words on the
top of the screen, accompanied by possible correct spellings, and allow editing, via a series of commands.

Options
-b
Back up original file in filename. bak.
-d file
Search file instead of standard dictionary file.
-m
Suggest different root/ affix combinations.
-n
Expect nroff or troff input file.
-p file
Search file instead of personal dictionary file.
-t
Expect TeX or LaTeX input file.
-w chars
Consider chars to be legal, in addition to a-z and A-Z.
-x
Do not back up original file.
-B
Search for missing blanks (resulting in concatenated words) in addition to ordinary misspellings.
-C
Do not produce error messages in response to concatenated words.
-L number
Show number lines of context.
-M

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List interactive commands at bottom of screen.

-N
Suppress printing of interactive commands.
-P
Do not attempt to suggest more root/ affix combinations.
-S
Sort suggested replacements by likelihood that each is correct.
-T type
Expect all files to be formatted by type.
-W n
Never consider words that are n characters or less to be misspelled.
-V
Use hat notation (^ L) to display control characters and M-to display characters with the high bit set.
Interactive Commands
?
Display help screen.
space character
Accept the word in this instance.
number
Replace with suggested word that corresponds to number.
!command
Invoke shell and execute command in it. Prompt before exiting.
a
Accept word as correctly spelled, but do not add it to personal dictionary.
i
Accept word and add it (capitalized, if so in file) to personal dictionary.
l
Search system dictionary for words.
q
Exit without saving.

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r

Replace word.
u
Accept word and add lowercase version of it to personal dictionary.
x
Skip to the next file, saving changes.
^L
Redraw screen.
^Z
Suspend ispell.

join join [options] file1 file2
Join lines of two sorted files by matching on a common field. If either file1 or file2 is -, read from standard input.
Options
-a filenum
Print a line for each unpairable line in file filenum, in addition to the normal output.
-e string
Replace missing input fields with string.
-i, --ignore-case
Ignore case differences when comparing keys.
-1 fieldnum1
Join field in file1 is fieldnum1. Default is the first field.
-2 fieldnum2
Join field in file2 is fieldnum2. Default is the first field.
-o fieldlist
Order the output fields according to fieldlist, where each entry in the list is in the form filenum. fieldnum.
Entries are separated by commas or blanks.

-t char
Specifies the field-separator character (default is whitespace ).
-v filenum
Print only unpairable lines from file filenum.
--help

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Print help message and then exit.
--version
Print the version number and then exit.

kbd_ mode kbd_ mode [option]
Print or set the current keyboard mode, which may be RAW, MEDIUMRAW, or XLATE.
Options
-a
Set mode to XLATE (ASCII mode).
-k
Set mode to MEDIUMRAW (keycode mode).
-s
Set mode to RAW (scancode mode).
-u
Set mode to UNICODE (UTF-8 mode).

kbdrate kbdrate [options]
System administration command. Control the rate at which the keyboard repeats characters, as well as its delay
time. Using this command without options sets a repeat rate of 10.9 characters per second; the default delay is
250 milliseconds. When Linux boots, however, it sets the keyboard rate to 30 characters per second.

Options
-s
Suppress printing of messages.
-r rate
Specify the repeat rate, which must be one of the following numbers (all in characters per second): 2.0,
2.1, 2.3, 2.5, 2.7, 3.0, 3.3, 3.7, 4.0, 4.3, 4.6, 5.0, 5.5, 6.0, 6.7, 7.5, 8.0, 8.6, 9.2, 10.0, 10.9, 12.0, 13.3,
15.0, 16.0, 17.1, 18.5, 20.0, 21.8, 24.0, 26.7, or 30.0.

-d delay
Specify the delay, which must be one of the following (in milliseconds): 250, 500, 750, or 1000.

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kerneld kerneld
System administration command. kerneld automatically loads kernel modules when they are needed, thereby
reducing kernel memory usage from unused loaded modules and replacing manual loading of modules with
modprobe or insmod. If a module has not been used for more than one minute, kerneld automatically removes
it.

kerneld comes with the modules-utilities package and is set up during kernel configuration; its functionality is
provided by interactions between that package and the kernel. kerneld is aware of most common types of
modules. When more than one possible module can be used for a device (such as a network driver), kerneld
uses the configuration file /etc/ conf. modules, which contains path information and aliases for all loadable
modules, to determine the correct module choice.

kerneld can also be used to implement dial-on-demand networking, such as SLIP or PPP connections. The
network connection request can be processed by kerneld to load the proper modules and set up the connection to
the server.

kill kill [option] IDs
This is the /bin/ kill command; there is also a shell command of the same name. Send a signal to terminate one or
more process IDs. You must own the process or be a privileged user. If no signal is specified, TERM is sent.

Options
-l
List all signals.
-p
Print the process ID of the named process, but don't send it a signal. To use this option, specify the full
path (e. g., /bin/ kill -p).

-signal
The signal number (from /usr/ include/ sys/ signal. h) or name (from kill -l). With a signal number of 9
(HUP), the kill cannot be caught by the process; use this to kill a process that a plain kill doesn't
terminate. The default is TERM.

killall killall [options] names
Kill processes by command name. If more than one process is running the specified command, kill all of them.
Treat command names that contain a / as files; kill all processes that are executing that file.

Options
-signal
Send signal to process (default is TERM). signal may be a name or number.
-e
Require an exact match to kill very long names (i. e., longer than 15 characters). Normally, killall kills
everything that matches within the first 15 characters. With -e, such entries are skipped. (Use -v to print a
message for each skipped entry.)

-g
Kill the process group to which the process belongs.

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-i

Prompt for confirmation before killing processes.
-l
List known signal names.
-q
Quiet; do not complain of processes not killed.
-v
Verbose: after killing process, report success and process ID.
-V
Print version information.
-w
Wait for all killed processes to die. Note that killall may wait forever if the signal was ignored or had no
effect, or if the process stays in zombie state.

killall5 killall5
The System V equivalent of killall, this command kills all processes except those on which it depends.

klogd klogd [options]
System administration command. Control which kernel messages are displayed on the console; prioritize all
messages, and log them through syslogd. On many operating systems, syslogd performs all the work of klogd,
but on Linux the features are separated. Kernel messages are gleaned from the /proc filesystem and from system
calls to syslogd. By default, no messages appear on the console. Messages are sorted into 8 levels, 0-7, and the
level number is prepended to each message.

Priority levels
0
Emergency situation (KERN_ EMERG).
1
A crucial error has occurred (KERN_ ALERT).
2
A serious error has occurred (KERN_ CRIT).
3
An error has occurred (KERN_ ERR).
4
A warning message (KERN_ WARNING).

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5

The situation is normal but should be checked (KERN_ NOTICE).
6
Information only (KERN_ INFO).
7
Debugging messages (KERN_ DEBUG).
Options
-c level
Print all messages of a higher priority (lower number) than level to the console.
-d
Debugging mode.
-f file
Print all messages to file; suppress normal logging.
-k file
Use file as source of kernel symbols.
-n
Avoid autobackgrounding. This is needed when klogd is started from init.
-o
One-shot mode. Prioritize and log all current messages, then immediately exit.
-s
Suppress reading of messages from the /proc filesystem.
Files
/usr/ include/ linux/ kernel. h, /usr/ include/ sys/ syslog. h
Sources for definitions of each logging level
/proc/ kmsg
A file examined by klogd for messages
/var/ run/ klogd. pid
klogd's process ID

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ksyms ksyms [options]
System administration command. Print a list of all exported kernel symbols (name, address, and defining
module, if applicable).

Options
-a
Include symbols from unloaded modules.
-h
Suppress header message.
-m
Include starting address and size. Useful only for symbols in loaded modules.
File
/proc/ ksyms
Another source of the same information

lastlog lastlog [options]
System administration command. Print the last login times for system accounts. Login information is read from
the file /var/ log/ lastlog.

Options
-tn
Print only logins more recent than n days ago.
-uname
Print only login information for user name.

ld ld [options] objfiles
Combine several objfiles, in the specified order, into a single executable object module (a. out by default). ld is
the link editor and is often invoked automatically by compiler commands.

Options
-c file
Consult file for commands.
-d, -dc, -dp
Force the assignment of space to common symbols.
-defsym symbol= expression
Create the global symbol with the value expression.

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-e symbol

Set symbol as the address of the output file's entry point.
-i
Produce a linkable output file; attempt to set its magic number to OMAGIC.
-larch
Include the archive file arch in the list of files to link.
-m linker
Emulate linker.
-n
Make text read-only; attempt to set NMAGIC.
-noinhibit-exec
Produce output file even if errors are encountered.
-o output
Place output in output, instead of a. out.
-oformat format
Specify output format.
-r
Produce a linkable output file; attempt to set its magic number to OMAGIC.
-s
Do not include any symbol information in output.
-shared
Create a shared library.
-sort-common
Do not sort global common symbols by size.
-t
Announce each input file's name as it is processed.
-u symbol
Force symbol to be undefined.
-v, --version
Show version number.
--verbose
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Print information about ld; print the names of input files while attempting to open them.
-warn-common
Warn when encountering common symbols combined with other constructs.
-warn-once
Provide only one warning per undefined symbol.
-x
With -s or -S, delete all local symbols that begin with L.
-L dir
Search directory dir before standard search directories (this option must precede the -l option that
searches that directory).

-M
Display a link map on standard out.
-Map file
Print a link map to file.
-N
Allow reading of and writing to both data and text; mark ouput if it supports Unix magic numbers; do not
page-align data.

-R file
Obtain symbol names and addresses from file, but suppress relocation of file and its inclusion in output.
-S
Do not include debugger symbol information in output.
-Tbss address
Begin bss segment of output at address.
-Tdata address
Begin data segment of output at address.
-Ttext address
Begin text segment of output at address.
-Ur
Synonymous with -r except when linking C++ programs, where it resolves constructor references.
-X
With -s or -S, delete local symbols beginning with L.

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-V

Show version number and emulation linkers for -m option.

ldconfig ldconfig [options] directories
System administration command. Examine the libraries in the given directories, /etc/ ld. so. conf, /usr/ lib, and /lib;
update links and cache where necessary. Usually run in startup files or after the installation of new shared
libraries.

Options
-D
Debug. Suppress all normal operations.
-l
Library mode. Expect libraries as arguments, not directories. Manually link specified libraries.
-n
Suppress examination of /usr/ lib and /lib and reading of /etc/ ld. so. conf; do not cache.
-N
Do not cache; only link.
-p
Print all directories and candidate libraries in the cache. Expects no arguments.
-v
Verbose. Include version number, and announce each directory as it is scanned and links as they are
created.

-X
Do not link; only rebuild cache.
Files
/lib/ ld. so
Linker and loader.
/etc/ ld. so. conf
List of directories that contain libraries.
/etc/ ld. so. cache
List of the libraries found in those libraries mentioned in /etc/ ld. so. conf.

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ldd ldd [options] programs
Display a list of the shared libraries each program requires.
Options
-v
Display ldd's version.
-V
Display the linker's version.

less less [options] [filename]
less is a program for paging through files or other output. It was written in reaction to the perceived
primitiveness of more (hence its name). Some commands may be preceded by a number.

Options
-[ z] num
Set number of lines to scroll to num. Default is one screenful. A negative num sets the number to num
lines less than the current number.

+[+] command
Run command on startup. If command is a number, jump to that line. The option ++ applies this
command to each file in the command-line list.

-?
Print help screen. Ignore all other options; do not page through file.
-a
When searching, begin after last line displayed. (Default is to search from second line displayed.)
-bbuffers
Use buffers buffers for each file (default is 10). Buffers are 1 kilobyte in size.
-c
Redraw screen from top, not bottom.
-d
Suppress dumb-terminal error messages.
-e
Automatically exit after reaching EOF twice.
-f
Force opening of directories and devices; do not print warning when opening binaries.

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-g

Highlight only string found by past search command, not all matching strings.
-hnum
Never scroll backward more than num lines at once.
-i
Make searches case-insensitive, unless the search string contains uppercase letters.
-jnum
Position target line on line num of screen. Target line can be the result of a search or a jump. Count lines
beginning from 1 (top line). A negative num is counted back from bottom of screen.

-kfile
Read file to define special key bindings.
-m
Display more-like prompt, including percent of file read.
-n
Do not calculate line numbers. Affects -m and -M options and = and v commands (disables passing of
line number to editor).

-ofile
When input is from a pipe, copy output to file as well as to screen. (Prompt for overwrite authority if file
exists.)

-ppattern
At startup, search for first occurrence of pattern.
m
Set medium prompt (specified by -m).
M
Set long prompt (specified by -M).
=
Set message printed by = command.
-q
Disable ringing of bell on attempts to scroll past EOF or before beginning of file. Attempt to use visual
bell instead.

-r
Display "raw" control characters, instead of using ^x notation. Sometimes leads to display problems.
-s

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Print successive blank lines as one line.
-ttag
Edit file containing tag. Consult ./ tags (constructed by ctags).
-u
Treat backspaces and carriage returns as printable input.
-w
Print lines after EOF as blanks instead of tildes (~).
-xn
Set tab stops to every n characters. Default is 8.
-yn
Never scroll forward more than n lines at once.
-B
Do not automatically allocate buffers for data read from a pipe. If -b specifies a number of buffers,
allocate that many. If necessary, allow information from previous screens to be lost.

-C
Redraw screen by clearing it and then redrawing from top.
-E
Automatically exit after reaching EOF once.
-G
Never highlight matching search strings.
-I
Make searches case-insensitive, even when the search string contains uppercase letters.
-M
Prompt more verbosely than with -m, including percentage, line number, and total lines.
-N
Print line number before each line.
-Ofile
Similar to -o but does not prompt when overwriting file.
-P[ m, M,=] prompt
Set prompt (as defined by -m, -M, or =). Default is short prompt (-m).
-Q

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Never ring terminal bell.
-S
Cut, do not fold, long lines.
-Tfile
With the -t option or :t command, read file instead of ./ tags.
-U
Treat backspaces and carriage returns as control characters.
-X
Do not send initialization and deinitialization strings from termcap to terminal.
Commands
Many commands can be preceded by a numeric argument, referred to as number in the command descriptions.
SPACE, ^V, f, ^F
Scroll forward the default number of lines (usually one windowful).
z
Similar to SPACE but allows the number of lines to be specified, in which case it resets the default to that
number.

RETURN, ^N, e, ^E, j, ^J
Scroll forward. Default is one line. Display all lines, even if the default is more lines than the screen size.
d, ^D
Scroll forward. Default is one-half the screen size. The number of lines may be specified, in which case
the default is reset.

b, ^B, ESC-v
Scroll backward. Default is one windowful.
w
Like b but allows the number of lines to be specified, in which case it resets the default to that number.
y, ^Y, ^P, k, ^K
Scroll backward. Default is one line. Display all lines, even if the default is more lines than the screen
size.

u, ^U
Scroll backward. Default is one-half the screen size. The number of lines may be specified, in which case
the default is reset.

r, ^R, ^L

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Redraw screen.

R
Like r but discard buffered input.
F
Scroll forward. When an EOF is reached, continue trying to find more output, behaving similarly to tail -f.

g, <, ESC-<
Skip to a line. Default is 1.
G, >, ESC->
Skip to a line. Default is the last one.
p, %
Skip to a position number percent of the way into the file.
{
If the top line on the screen includes a {, find its matching }. If the top line contains multiple {s, use
number to determine which one to use in finding a match.

}
If the bottom line on the screen includes a }, find its matching {. If the bottom line contains multiple }s,
use number to determine which one to use in finding a match.

(
If the top line on the screen includes a (, find its matching ). If the top line contains multiple (s, use
number to determine which one to use in finding a match.

)
If the bottom line on the screen includes a ), find its matching (. If the bottom line contains multiple )s,
use number to determine which one to use in finding a match.

[
If the top line on the screen includes a [, find its matching ]. If the top line contains multiple [s, use
number to determine which one to use in finding a match.

]
If the bottom line on the screen includes a ], find its matching [. If the bottom line contains multiple ]s,
use number to determine which one to use in finding a match.

ESC-^ F
Behave like { but prompt for two characters, which it substitutes for { and } in its search.
ESC-^ B
Behave like } but prompt for two characters, which it substitutes for { and } in its search.

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m

Prompt for a lowercase letter and then use that letter to mark the current position.
'
Prompt for a lowercase letter and then go to the position marked by that letter. There are some special
characters:

'
Return to position before last "large movement."
^
Beginning of file.
$
End of file.
^X^ X
Same as '.
/pattern
Find next occurrence of pattern, starting at second line displayed. Some special characters can be entered
before pattern:

!
Find lines that do not contain pattern.
*
If current file does not contain pattern, continue through the rest of the files in the command line
list.

@
Search from the first line in the first file specified on the command line, no matter what the screen
currently displays.

?pattern
Search backward, beginning at the line before the top line. Treats !, *, and @ as special characters when
they begin pattern, as / does.

ESC-/ pattern
Same as /*.
ESC-? pattern
Same as ?*.
n
Repeat last pattern search.

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N

Repeat last pattern search, in the reverse direction.
ESC-n
Repeat previous search command but as though it were prefaced by *.
ESC-N
Repeat previous search command but as though it were prefaced by * and in the opposite direction.
ESC-u
Toggle search highlighting.
:e [filename]
Read in filename and insert it into the command-line list of filenames. Without filename, reread the
current file. filename may contain special characters:

%
Name of current file
#
Name of previous file
^X^ V, E
Same as :e.
:n
Read in next file in command-line list.
:p
Read in previous file in command-line list.
:x
Read in first file in command-line list.
:f, =, ^G
Print filename, position in command-line list, line number on top of window, total lines, byte number,
and total bytes.

-Expects
to be followed by a command-line option letter. Toggles the value of that option or, if
appropriate, prompts for its new value.

-+
Expects to be followed by a command-line option letter. Resets that option to its default.
--

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Expects to be followed by a command-line option letter. Resets that option to the opposite of its default,
where the opposite can be determined.

_
Expects to be followed by a command-line option letter. Display that option's current setting.
+command
Execute command each time a new file is read in.
q, :q, :Q, ZZ
Exit.
v
Not valid for all versions. Invoke editor specified by $VISUAL or $EDITOR, or vi if neither is set.
! [command]
Not valid for all versions. Invoke $SHELL or sh. If command is given, run it and then exit. Special
characters:

%
Name of current file
#
Name of previous file
!!
Last shell command
| mark-letter command
Not valid for all versions. Pipe fragment of file (from first line on screen to mark-letter) to command.
mark-letter may also be:

^
Beginning of file.
$
End of file.
., newline
Current screen is piped.
Prompts
The prompt interprets certain sequences specially. Those beginning with % are always evaluated. Those
beginning with ? are evaluated if certain conditions are true. Some prompts determine the position of particular
lines on the screen. These sequences require that a method of determining that line be specified. See the -P
option and the manpage for more information.

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ln ln [options] sourcename [destname]
ln [options] sourcenames destdirectory
Create pseudonyms (links) for files, allowing them to be accessed by different names. In the first form, link
sourcename to destname, where destname is usually a new filename, or (by default) the current directory. If
destname is an existing file, it is overwritten; if destname is an existing directory, a link named sourcename is
created in that directory. In the second form, create links in destdirectory, each link having the same name as the
file specified.

Options
-b, --backup
Back up files before removing the originals.
-d, -F, --directory
Allow hard links to directories. Available to privileged users.
-f, --force
Force the link (don't prompt for overwrite permission).
--help
Print a help message and then exit.
-i, --interactive
Prompt for permission before removing files.
-n, --no-dereference
Replace symbolic links to directories instead of dereferencing them. --force is useful with this option.
-s, --symbolic
Create a symbolic link. This lets you link across filesystems and also see the name of the link when you
run ls -l (otherwise, there's no way to know the name that a file is linked to).

-S suffix, --suffix suffix
Append suffix to files when making backups, instead of the default ~.
-v, --verbose
Verbose mode.
--version
Print version information and then exit.
-V, --version-control value
Control the types of backups made. The acceptable values for version-control are:
t, numbered
Numbered.

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nil, existing
Simple (~) unless a numbered backup exists; then make a numbered backup.
never, simple
Simple.

locate locate [options] pattern
Search database( s) of filenames and print matches. *, ?, [, and ] are treated specially; / and . are not. Matches
include all files that contain pattern, unless pattern includes metacharacters, in which case locate requires an
exact match.

Options
-d path, --database= path
Search databases in path. path must be a colon-separated list.
-h, --help
Print a help message and then exit.
--version
Print version information and then exit.

lockfile lockfile [options] filenames
Create semaphore file( s), used to limit access to a file. When lockfile fails to create some of the specified files, it
pauses for 8 seconds and retries the last one on which it failed. The command processes flags as they are
encountered (i. e., a flag that is specified after a file will not affect that file).

Options
-sleeptime
Time lockfile waits before retrying after a failed creation attempt. Default is 8 seconds.
-!
Invert return value. Useful in shell scripts.
-l lockout_ time
Time (in seconds) after a lockfile was last modified at which it will be removed by force. See also -s.
-ml, -mu
If the permissions on the system mail spool directory allow it or if lockfile is suitably setgid, it can lock
and unlock your system mailbox with the options -ml and -mu, respectively.

-r retries
Stop trying to create files after retries retries. The default is -1 (never stop trying). When giving up,
remove all created files.

-s suspend_ time

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After a lockfile has been removed by force (see -l), a suspension of 16 seconds takes place by default.
(This is intended to prevent the inadvertent immediate removal of any lockfile newly created by another
program.) Use -s to change the default 16 seconds.

logger logger [options] [message...]
TCP/ IP command. Add entries to the system log (via syslogd). A message can be given on the command line, or
standard input is logged.

Options
-f file
Read message from file.
-i
Include the process ID of the logger process.
-p pri
Enter message with the specified priority pri. Default is user. notice.
-t tag
Mark every line in the log with the specified tag.

login login [name | option]
Log in to the system. login asks for a username (name can be supplied on the command line) and password (if
appropriate).

If successful, login updates accounting files, sets various environment variables, notifies users if they have mail,
and executes startup shell files.

Only the root user can log in when /etc/ nologin exists. That file is displayed before the connection is terminated.
Furthermore, root may connect only on a tty that is listed in /etc/ securetty. If ~/. hushlogin exists, execute a quiet
login. If /var/ adm/ lastlog exists, print the time of the last login.

Options
-f
Suppress second login authentication.
-h host
Specify name of remote host. Normally used by servers, not humans; may be used only by root.
-p
Preserve previous environment.

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logname logname [option]
Consult /var/ run/ utmp for user's login name. If found, print it; otherwise, exit with an error message.
Options
--help
Print a help message and then exit.
--version
Print version information and then exit.

logrotate logrotate [options] config_ files
System administration command. Manipulate log files according to commands given in config_ files.
Options
-d
Debug mode. No changes will be made to log files.
-s, --state file
Save state information in file. The default is /var/ lib/ logrotate. status.
--usage
Usage version and copyright information.
Commands
compress
Compress old versions of log files with gzip.
copytruncate
Copy log file, then truncate it in place. For use with programs whose logging cannot be temporarily
halted.

create [permissions] [owner] [group]
After rotation, re-create log file with the specified permissions, owner, and group. permissions must be in
octal. If any of these parameters is missing, the log file's original attributes will be used.

daily
Rotate log files every day.
delaycompress
Don't compress log file until the next rotation.
errors address
Mail any errors to the given address.

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endscript

End a postrotate or prerotate script.
ifempty
Rotate log file even if it is empty. Overrides the default notifempty option.
include file
Read the file into current file. If file is a directory, read all files in that directory into the current file.
mail address
Mail any deleted logs to address.
monthly
Rotate log files only the first time logrotate is run in a month.
nocompress
Override compress.
nocopytruncate
Override copytruncate.
nocreate
Override create.
nodelaycompress
Override delaycompress.
noolddir
Override olddir.
notifempty
Override ifempty.
olddir directory
Move logs into directory for rotation. directory must be on the same physical device as the original log
files.

postrotate
Begin a script of directives to apply after the log file is rotated. The script ends when the endscript
directive is read.

prerotate
Begin a script of directives to apply before a log file is rotated. The script ends when the endscript
directive is read.

rotate number

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The number of times to rotate a log file before removing it.

size n[ k| M]
Rotate log file when it is greater than n bytes. n can optionally be followed by k for kilobytes or M for
megabytes.

look look [options] string [file]
Search for lines in file (/ usr/ dict/ words by default) that begin with string.
Options
-a
Use alternate dictionary /usr/ dict/ web2.
-d
Compare only alphanumeric characters.
-f
Search is not case-sensitive.
-t character
Stop checking after the first occurrence of character.

lpc lpc [command]
System administration command. Control line printer. If executed without a command, lpc will accept
commands from standard input.

Commands
?, help [commands]
Get a list of commands or help on specific commands.
abort all| printer
Terminate current printer daemon and disable printing for the specified printer.
clean all| printer
Remove files that cannot be printed from the specified printer queues.
disable all| printer
Disable specified printer queues.
down all| printer message
Disable specified printer queues and put message in the printer status file.
enable all| printer
Enable the specified printer queues.

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exit, quit
Exit lpc.
restart all| printer
Try to restart printer daemons for the specified printers.
start all| printer
Enable the printer queues and start printing daemons for the specified printers.
status all| printer
Return the status of the specified printers.
stop all| printer
Disable the specified printer daemons after any current jobs are completed.
topq printer [jobnumbers] [users]
Put the specifed jobs at the top of the printer's queue in the order the jobs are listed.
up all| printer
Enable print queues and restart daemons for the specified printers.

lpd lpd [option] [port]
TCP/ IP command. Line printer daemon. lpd is usually invoked at boot time from the rc2 file. It makes a single
pass through the printer configuration file (traditionally /etc/ printcap) to find out about the existing printers and
prints any files left after a crash. It then accepts requests to print files in a queue, transfer files to a spooling area,
display a queue's status, or remove jobs from a queue. In each case, it forks a child process for each request, then
continues to listen for subsequent requests. If port is specified, lpd listens on that port; otherwise, it uses the
getservbyname call to ascertain the correct port.

The file lock in each spool directory prevents multiple daemons from becoming active simultaneously. After the
daemon has set the lock, it scans the directory for files beginning wth cf. Lines in each cf file specify files to be
printed or nonprinting actions to be performed. Each line begins with a key character, which specifies
information about the print job or what to do with the remainder of the line. Key characters are:

C
Classification --string to be used for the classification line on the burst page.
c
cifplot file.
f
Formatted file --name of a file to print that is already formatted.
g
Graph file.
H

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Hostname --name of machine where lpd was invoked.
J
Job name --string to be used for the jobname on the burst page.
L
Literal --this line contains identification information from the password file and causes the banner page
to be printed.

l
Formatted file, but suppress page breaks and printing of control characters.
M
Mail --send mail to the specified user when the current print job completes.
n
ditroff file.
P
Person --login name of person who invoked lpd.
r
DVI file.
T
Title --string to be used as the title for pr.
t
troff file.
U
Unlink --name of file to remove upon completion of printing.
Option
-l
Enable logging of all valid requests.
Files
/etc/ printcap
Printer description file
/var/ spool/*
Spool directories
/var/ spool/*/ minfree

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Minimum free space to leave
/dev/ lp*
Printer devices
/etc/ hosts. equiv
Machine names allowed printer access
/etc/ hosts. lpd
Machine names allowed printer access, but not under same administrative control

lpq lpq [options] [user]
Check the print spool queue for status of print jobs. For each job, display username, rank in the queue,
filenames, job number, and total file size (in bytes). If user is specified, display information only for that user.

Options
-l
Print information about each file comprising a job.
-Pprinter
Specify which printer to query. Without this option, lpq uses the printer set in the PRINTER environment
variable or the default system printer.

num
Check status for job number num.

lpr lpr [options] files
Send files to the printer spool queue.
Options
-c
Expect data produced by cifplot.
-d
Expect data produced by TeX in the DVI (device-independent) format.
-f
Use a filter that interprets the first character of each line as a standard carriage control character.
-g
Expect standard plot data as produced by the plot routines.
-l
Use a filter that allows control characters to be printed and suppresses page breaks.

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-n
Expect data from ditroff (device-independent troff).
-p
Use pr to format the files.
-t
Expect data from troff (phototypesetter commands).
-v
Expect a raster image for devices like the Benson Varian.
-Pprinter
Output to printer instead of the printer specified in the PRINTER environment variable or the system
default.

-h
Do not print the burst page.
-m
Send mail to notify of completion.
-r
Remove the file upon completion of spooling. Cannot be used with the -s option.
-s
Use symbolic links instead of copying files to the spool directory. This can save time and disk space for
large files. Files should not be modified or removed until they have been printed.

-# num
Print num copies of each listed file.
-C string
Replace system name on the burst page with string.
-J name
Replace the job name on the burst page with name. If omitted, uses the first file's name.
-T title
Use title as the title when using pr.
-i [cols]
Indent the output. Default is 8 columns. Specify number of columns to indent with the cols argument.
-w num

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Set num characters as the page width for pr.

lprm lprm [options] [jobnum] [user]
Remove a print job from the print spool queue. You must specify a job number or numbers, which can be
obtained from lpq. A privileged user may use the user parameter to remove all files belonging to a particular
user or users.

Options
-Pprinter
Specify printer name. Normally, the default printer or printer specified in the PRINTER environment
variable is used.

-Remove
all jobs in the spool owned by user.

lpstat lpstat [options]
Show the status of the print queue. With options that take a list argument, omitting the list produces all
information for that option. list can be separated by commas or, if enclosed in double quotes, by spaces.

Options
-a [list]
Show whether the list of printer or class names is accepting requests.
-c [list]
Show information about printer classes named in list.
-d
Show the default printer destination.
-f [list]
Verify that the list of forms is known to lp.
-l
Use after -f to describe available forms, after -p to show printer configurations, or after -s to describe
printers appropriate for the specified character set or print wheel.

-o [list]
Show the status of output requests. list contains printer names, class names, or request IDs.
-p [list]
Show the status of printers named in list.
-r
Show whether the print scheduler is on or off.

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-R

Show the job's position in the print queue.
-s
Summarize the print status (shows almost everything).
-t
Show all status information (reports everything).
-u [list]
Show request status for users on list. list can be all to show information on all users.
-v [list]
Show device associated with each printer named in list.

lptest lptest [length] [count]
Generate a lineprinter test pattern on standard output. Prints a standard ripple pattern of all printable ASCII
characters, offset by one position on each succeeding line.

Parameters
length
Specify the output line length (default is 79).
count
Specify the number of lines to print (default is 200).

ls ls [options] [names]
List contents of directories. If no names are given, list the files in the current directory. With one or more names,
list files contained in a directory name or that match a file name. names can include filename metacharacters.
The options let you display a variety of information in different formats. The most useful options include -F, -R, -l,
and -s. Some options don't make sense together (e. g., -u and -c).

Options
-1, --format= single-column
Print one entry per line of output.
-a
List all files, including the normally hidden files whose names begin with a period.
-b, --escape
Display nonprinting characters in octal and alphabetic format.
-c, --time-ctime, --time= status
List files by status change time (not creation/ modification time).

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--color, --colour, --color= yes, --colour= yes
Colorize the names of files depending on the type of file.
--color= no, --colour= no
Disables colorization. This is the default. Provided to override a previous color option.
--color= tty, --colour= tty
Same as --color, but only if standard output is a terminal. Very useful for shell scripts and command
aliases, especially if your favorite pager does not support color control codes.

-d, --directory
Report only on the directory, not its contents.
-f
Print directory contents in exactly the order in which they are stored, without attempting to sort them.
--full-time
List times in full, rather than use the standard abbreviations.
--help
Print a help message and then exit.
-i, --inode
List the inode for each file.
-k, --kilobytes
If file sizes are being listed, print them in kilobytes. This option overrides the environment variable
POSIXLY_ CORRECT.

-l, --format= long, --format= verbose
Long format listing (includes permissions, owner, size, modification time, etc.).
-m, --format= commas
Merge the list into a comma-separated series of names.
-n, --numeric-uid-gid
Like -l, but use group-ID and user-ID numbers instead of owner and group names.
-p
Mark directories by appending / to them.
-q, --hide-control-chars
Show nonprinting characters as ?.-r, --reverse

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List files in reverse order (by name or by time).

-s, --size
Print size of the files in blocks.
-t, --sort= time
Sort files according to modification time (newest first).
-u, --time= atime, --time= access, --time= use
Sort files according to the file access time.
--version
Print version information on standard output, then exit.
-x, --format= across, --format= horizontal
List files in rows going across the screen.
-A, --almost-all
List all files, including the normally hidden files whose names begin with a period. Does not include the .
and . directories.

-B, --ignore-backups
Do not list files ending in ~, unless given as arguments.
-C, --format= vertical
List files in columns (the default format).
-F, --classify
Flag filenames by appending / to directories, * to executable files, @ to symbolic links, | to FIFOs, and
= to sockets.

-G, --no-group
In long format, do not display group name.
-I, --ignore pattern
Do not list files whose names match the shell pattern pattern, unless they are given on the command line.
-L, --dereference
List the file or directory referenced by a symbolic link rather than the link itself.
-N, --literal
Do not list filenames.
-Q, --quote-name
Quote filenames with "; quote nongraphic characters with alphabetic and octal backslash sequences.
-R, --recursive

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Recursively list subdirectories as well as the specified (or current) directory.
-S, --sort= size
Sort by file size, largest to smallest.
-T, --tabsize n_ cols
Assume that each tabstop is n_ cols columns wide. The default is 8.
-U, --sort= none
Do not sort files. Similar to -f but display in long format.
-X, --sort= extension
Sort by file extension.
Examples
List all files in the current directory and their sizes; use multiple columns and mark special files:
ls -asCFList the status of directories /bin and /etc:
ls -ld /bin /etcList C source files in the current directory, the oldest first:
ls -rt *. cCount the nonhidden files in the current directory:
ls | wc -l

lsattr lsattr [options] [files]
Print attributes of files on a Linux Second Extended File System. See also chattr.
Options
-a
List all files in specified directories.
-d
List directories' attributes, not the attributes of the contents.
-R
List directories and their contents recursively.
-v
List version of files.
-V

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List version and then exit.

lsmod lsmod
System administration command. List all loaded modules: their name, size (in 4KB units) and, if appropriate, a
list of referring modules.

File
/proc/ modules
Source of the same information.

m4 m4 [options] [macros] [files]
Macro processor for C and other files.
Options
-e, --interactive
Operate interactively, ignoring interrupts.
-dflags, --debug= flags
Specify flag-level debugging.
-ln, --arglength= n
Specify the length of debugging output.
-o file, --error-output= file
Place output in file. Despite the name, print error messages on standard error.
-p, --prefix-built-ins
Prepend m4_ to all built-in macro names.
-s, --synclines
Insert #line directives for the C preprocessor.
-Bn
Set the size of the push-back and argument collection buffers to n (default is 4096).
-Dname[= value], --define= name[= value]
Define name as value or, if value is not specified, define name as null.
-E, --fatal-warnings
Consider all warnings to be fatal, and exit after the first of them.
-Ffile, --freeze-state file
Record m4's frozen state in file, for later reloading.

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-G, --traditional
Behave like traditional m4, ignoring GNU extensions.
-Hn, --hashsize= n
Set symbol-table hash array to n (default is 509).
-Idirectory, --include= directory
Search directory for include files.
-Q, --quiet, --silent
Suppress warning messages.
-Rfile, --reload-state file
Load state from file before starting execution.
-Uname, --undefine= name
Undefine name.

mail mail [options] [users]
Read mail or send mail to other users. The mail utility allows you to compose, send, receive, forward, and reply
to mail. mail has two main modes: compose mode, in which you create a message, and command mode, in
which you manage your mail.

While mail is a powerful utility, it can be tricky for a novice user. Most Linux distributions include pine and
elm, which are much easier to use.

This section presents mail commands, options, and files. To get you started, here are two of the most basic
commands.

To enter interactive mail-reading mode, type:
mailTo begin writing a message to user, type:
mail userEnter the text of the message, one line at a time, pressing Enter at the end of each line. To end the message, enter
a single period (.) in the first column of a new line, and press Enter.

Command-line options
-b list
Set blind carbon copy field to comma-separated list.
-c list
Set carbon copy field to comma-separated list.
-d

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Print debugging information.

-f [file]
Process contents of file, instead of /var/ spool/ mail/$ user. If file is omitted, process mbox in the user's
home directory.

-i
Do not respond to tty interrupt signals.
-n
Do not consult /etc/ mail. rc when starting up.
-p
Read mail in POP mode.
-s subject
Set subject to subject.
-u
Process contents of /var/ spool/ mail/$ user. Default.
-v
Verbose. Print information about mail delivery to standard out.
-I
Interactive --even when standard input has been redirected from the terminal.
-N
When printing a mail message or entering a mail folder, do not display message headers.
-P
Disable POP mode.
Compose-mode commands
~!
Execute a shell escape from compose mode.
~?
List compose mode escapes.
~b names
Add names to or edit the Bcc: header.
~c names
Add names to or edit the Cc: header.

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~d

Read in the dead. letter file.
~e
Invoke text editor.
~f messages
Insert messages into message being composed.
~F messages
Similar to ~f, but include message headers.
~h
Add to or change all the headers interactively.
~m messages
Similar to ~f, but indent with a tab.
~M messages
Similar to ~m, but include message headers.
~p
Print message header fields and message being sent.
~q
Abort current message composition.
~r filename
Append file to current message.
~s string
Change Subject: header to string.
~t names
Add names to or edit the To list.
~v
Invoke editor specified with the VISUAL environment variable.
~| command
Pipe message through command.
~: mail-command
Execute mail-command.

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~~ string

Insert string in text of message, prefaced by a single tilde (~). If string contains a ~, it must be escaped
with a \.

Command-mode commands

? List summary of commands (help screen).
! Execute a shell command.
-num Print numth previous message; defaults to immediately previous.
alias (a) Print or create alias lists.
alternates (alt) Specify remote accounts on remote machines that are yours. Tell mail not to reply to them.
chdir (c) cd to home or specified directory.
copy (co) Similar to save, but do not mark message for deletion.
delete (d) Delete message.
dp Delete current message and display next one.
edit (e) Edit message.
exit (ex, x) Exit mail without updating folder.
file (fi) Switch folders.
folder (fold) Read messages saved in a file. Files can be:
# Previous
% System mailbox
%user user's system mailbox
& mbox
+folder File in folder directory.
folders List folders.
headers (h) List message headers at current prompt.
headers+ (h+) Move forward one window of headers.
headers-(h-) Move back one window of headers.
help Same as ?.
hold (ho) Hold messages in system mailbox.
ignore Append list of fields to ignored fields.
mail user (m) Compose message to user.
mbox Default. Move specified messages to mbox on exiting.
next (n) Type next message or next message that matches argument.
preserve (pr) Synonym for hold.
print [list] (p) Display each message in list.
Print [list] (P) Similar to print, but include header fields.
quit (q) Exit mail and update folder.
reply (r) Send mail to all on distribution list.
Reply (R) Send mail to author only.
respond Same as reply.

retain Always include this list of header fields when printing messages. With no arguments, list retained fields.
save (s) Save message to folder.
saveignore Remove ignored fields when saving.
saveretain Override saveignore to retain specified fields.
set (se) Set or print mail options.
shell (sh) Enter a new shell.

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size Print size of each specified message.
source Read commands from specified file.
top Print first few lines of each specified message.
type (t) Same as print.
Type (T) Same as Print.
unalias Discard previously defined aliases.
undelete (u) Restore deleted message.
unread (U) Mark specified messages as unread.
unset (uns) Unset mail options.
visual (v) Edit message with editor specified by the VISUAL environment variable.
write (w) Write message, without header, to file.
xit (x) Same as exit.
z Move mail's attention to next windowful of text. Use z-to move it back.

mail options
These options are used inside of the .mailrc file. The syntax is set option or unset option.

append Append (do not prepend) messages to mbox.
ask Prompt for subject.
askbcc Prompt for blind carbon copy recipients.
askcc Prompt for carbon copy recipients.
asksub Prompt for Subject line.
autoprint Print next message after a delete.
chron Display messages in chronological order, most recent last.
debug Same as -d on command line.
dot Interpret a solitary . as an EOF.
folder Define directory to hold mail folders.
hold Keep message in system mailbox upon quitting.
ignore Ignore interrupt signals from terminal. Print them as @.
ignoreeof Do not treat ^D as an EOF.
metoo Do not remove sender from groups when mailing to them.
noheader Same as -N on command line.
nokerberos Retrieve POP mail via POP3, not KPOP, protocol.
nosave Do not save aborted letters to dead. letter.
pop-mail Retrieve mail with POP3 protocol, and save it in mbox. pop.
prompt Set prompt to a different string.
Replyall Switch roles of Reply and reply.
quiet Do not print version at startup.

searchheaders When given the specifier /x: y, expand all messages that contain the string y in the x header field.
verbose Same as -v on command line.
verbose-pop Display status while retrieving POP mail.

Special files
calendar Contains reminders that the operating system mails to you.
.maildelivery Mail delivery configuration file.
.mailrc Mail configuration file.

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triplog Keeps track of your automatic response recipients.
tripnote Contains automatic message.

mailq mailq [option]
System administration command. List all messages in the sendmail mail queue. Equivalent to sendmail -bp.
Option
-v
Verbose mode.

mailstats mailstats [options]
System administration command. Display a formatted report of the current sendmail mail statistics.
Options
-C file
Use sendmail configuration file file instead of the default sendmail. cf file.
-f file
Use sendmail statistics file file instead of the file specified in the sendmail configuration file.
-o
Don't show the name of the mailer in the report.

make make [options] [targets] [macro definitions]
Update one or more targets according to dependency instructions in a description file in the current directory. By
default, this file is called makefile or Makefile. Options, targets, and macro definitions can be in any order.
Macros definitions are typed as:

name= stringFor more information on make, see Managing Projects with make by Andrew Oram and Steve Talbott.
Options
-d, --debug
Print detailed debugging information.
-e, --environment-overrides
Override makefile macro definitions with environment variables.
-f makefile, --file= makefile, --makefile= makefile
Use makefile as the description file; a filename of -denotes standard input.
-h, --help
Print options to make command.
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-i, --ignore-errors
Ignore command error codes (same as .IGNORE).
-j [jobs], --jobs [= jobs]
Attempt to execute jobs jobs simultaneously, or, if no number is specified, as many jobs as possible.
-k, --keep-going
Abandon the current target when it fails, but keep working with unrelated targets.
-l [load], --load-average [= load], --max-load [= load]
Attempt to keep load below load, which should be a floating-point number. Used with -j.
-n, --just-print, --dry-run, --recon
Print commands but don't execute (used for testing).
-o file, --old-file= file, --assume-old= file
Never remake file or cause other files to be remade on account of it.
-p, --print-data-base
Print rules and variables in addition to normal execution.
-q, --question
Query; return 0 if file is up-to-date; nonzero otherwise.
-r, --no-built-in-rules
Do not use default rules.
-s, --silent, --quiet
Do not display command lines (same as .SILENT).
-t, --touch
Touch the target files, without remaking them.
-v, --version
Show version of make.
-w, --print-directory
Display the current working directory before and after execution.
--warn -undefined -variables
Print warning if a macro is used without being defined.
-C directory, --directory directory
cd to directory before beginning make operations. A subsequent -C directive will cause make to attempt

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to cd into a directory relative to the current working directory.

-I directory, --include-dir directory
Include directory in list of directories that contain included files.
-S, --no-keep-going, --stop
Cancel previous -k options. Useful in recursive makes.
-W file, --what-if file, --new-file file, --assume-new file
Behave as though file has been recently updated.
Description file lines
Instructions in the description file are interpreted as single lines. If an instruction must span more than one input
line, use a backslash (\) at the end of the line so that the next line is considered as a continuation. The description
file may contain any of the following types of lines:

Blanklines
Blank lines are ignored.
Commentlines
A pound sign (#) can be used at the beginning of a line or anywhere in the middle. make ignores
everything after the #.

Dependencylines
Depending on one or more targets, certain commands that follow will be executed. Possible formats
include:

targets : dependencies targets: dependencies ; command

Subsequent commands are executed if dependency files (the names of which may contain wildcards) do not exist
or are newer than a target. If no prerequisites are supplied, then subsequent commands are always executed
(whenever any of the targets are specified). No tab should precede any targets.

Suffixrules
These specify that files ending with the first suffix can be prerequisites for files ending with the second
suffix (assuming the root filenames are the same). Either of these formats can be used:

.suffix. suffix:.suffix:

The second form means that the root filename depends on the filename with the corresponding suffix.
Commands
Commands are grouped below the dependency line and are typed on lines that begin with a tab. If a
command is preceded by a hyphen (-), make ignores any error returned. If a command is preceded by an
at sign (@), the command line won't echo on the display (unless make is called with -n).

macrodefinitions
These have the following form:

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name = string

or
define name stringendef

Blank space is optional around the =.
includestatements
Similar to the C include directive, these have the form:
include filesInternal macros
$?
The list of prerequisites that have been changed more recently than the current target. Can be used only in
normal description file entries --not suffix rules.

$@
The name of the current target, except in description file entries for making libraries, where it becomes
the library name. Can be used both in normal description file entries and in suffix rules.

$<
The name of the current prerequisite that has been modified more recently than the current target.
$*
The name --without the suffix --of the current prerequisite that has been modified more recently than the
current target. Can be used only in suffix rules.

$%
The name of the corresponding .o file when the current target is a library module. Can be used both in
normal description file entries and in suffix rules.

$^
A space-separated list of all dependencies, with no duplications.
$+
A space-separated list of all dependencies, including duplications.
Pattern rules
These are a more general application of the idea behind suffix rules. If a target and a dependency both contain
%, GNU make will substitute any part of an existing filename. For instance, the standard suffix rule:

$( cc) -o $@ $<can be written as the following pattern rule:
%. o : %. c $( cc) -o $@ $<

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Macro modifiers
D
The directory portion of any internal macro name except $?. Valid uses are:

$(* D) $$(@ D) $(? D) $(< D) $(% D) $(@ D) $(^ D)

F
The file portion of any internal macro name except $?. Valid uses are:

$(* F) $$(@ F) $(? F) $(< F) $(% F) $(@ F) $(^ F)

Functions
$( subst from, to, string)
Replace all occurrences of from with to in string.
$( patsubst pattern, to, string)
Similar to subst, but treat % as a wildcard within pattern. Substitute to for any word in string that
matches pattern.

$( strip string)
Remove all extraneous whitespace.
$( findstring substring, mainstring)
Return substring if it exists within mainstring; otherwise, return null.
$( filter pattern, string)
Return those words in string that match at least one word in pattern. patterns may include the wildcard
%.

$( filter-out pattern, string)
Remove those words in string that match at least one word in pattern. patterns may include the wildcard
%.

$( sort list)
Return list, sorted in lexical order.
$( dir list)
Return the directory part (everything up to the last slash) of each filename in list.

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$( notdir list)
Return the nondirectory part (everything after the last slash) of each filename in list.
$( suffix list)
Return the suffix part (everything after the last period) of each filename in list.
$( basename list)
Return everything but the suffix part (everything up to the last period) of each filename in list.
$( addsuffix suffix, list)
Return each filename given in list with suffix appended.
$( addprefix prefix, list)
Return each filename given in list with prefix prepended.
$( join list1, list2)
Return a list formed by concatenating the two arguments, word by word (e. g., $( join a b,. c .o) becomes
a. c b. o).

$( word n, string)
Return the nth word of string.
$( words string)
Return the number of words in string.
$( firstword list)
Return the first word in the list list.
$( wildcard pattern)
Return a list of existing files in the current directory that match pattern.
$( origin variable)
Return one of the following strings that describes how variable was defined: undefined, default,
environment, environment override, file, command line, override, or automatic.

$( shell command)
Return the results of command. Any newlines in the result are to be converted to spaces. This function
works similarly to backquotes in most shells.

Macro string substitution
$( macro: s1= s2)
Evaluates to the current definition of $( macro), after substituting the string s2 for every occurrence of s1
that occurs either immediately before a blank or tab or at the end of the macro definition.

Special target names

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.DEFAULT:

Commands associated with this target are executed if make can't find any description file entries or suffix
rules with which to build a requested target.

.EXPORT_ ALL_ VARIABLES:
If this target exists, export all macros to all child processes.
.IGNORE:
Ignore error codes. Same as the -i option.
.PHONY:
Always execute commands under a target, even if it is an existing, up-to-date file.
.PRECIOUS:
Files you specify for this target are not removed when you send a signal (such as an interrupt) that aborts
make or when a command line in your description file returns an error.

.SILENT:
Execute commands, but do not echo them. Same as the -s option.
.SUFFIXES:
Suffixes associated with this target are meaningful in suffix rules. If no suffixes are listed, the existing list
of suffix rules is effectively "turned off."

makedbm makedbm [options] infile outfile
NFS/ NIS command. Make NIS dbm file. makedbm takes infile and converts it to a pair of files in ndbm
format, namely outfile. pag and outfile. dir. Each line of the input file is converted to a single dbm record. All
characters up to the first TAB or SPACE form the key, and the rest of the line is the data. If line ends with \&,
the data for that record is continued on to the next line. It is left for the NIS clients to interpret #; makedbm does
not treat it as a comment character. infile can be -, in which case the standard input is read.

makedbm generates a special entry with the key yp_ last_ modified, which is the date of infile (or the current
time, if infile is -).

Options
-b
Interdomain. Propagate a map to all servers using the interdomain name server named.
-d yp_ domain_ name
Create a special entry with the key yp_ domain_ name.
-i yp_ input_ file
Create a special entry with the key yp_ input_ file.
-l
Convert keys of the given map to lowercase.

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-m yp_ master_ name

Create a special entry with the key yp_ master_ name. If no master hostname is specified,
yp_ master_ name is set to the local hostname.

-o yp_ output_ file
Create a special entry with the key yp_ output_ name.
-s
Secure map. Accept connections from secure NIS networks only.
-u dbm filename
Undo a dbm file --print out a dbm file, one entry per line, with a single space separating keys from
values.

Example
It is easy to write shell scripts to convert standard files such as /etc/ passwd to the key value form used by
makedbm. For example, the awk program:

BEGIN { FS =":"; OFS = "\ t";} { print $1, $0}

takes the /etc/ passwd file and converts it to a form that can be read by makdbm to make the NIS file
passwd. byname. That is, the key is a username and the value is the remaining line in the /etc/ passwd file.

makemap makemap [options] type name
System administration command. Transfer from standard input to sendmail's database maps. Input should be
formatted as:

key value
You may comment lines with #, may substitute parameters with %n, and must escape literal % by entering it as
%%. The type must be dbm, btree, or hash. The name is a filename to which makemap appends standard
suffixes.

Options
-d
Allow duplicate entries. Valid only with btree type maps.
-f
Suppress conversion of uppercase to lowercase.
-N
Append a zero byte to each key.
-o
Append to existing file instead of replacing it.
-r

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If some keys already exist, replace them. (By default, makemap will exit when encountering a duplicated
key.)

-s
Ignore safety checks.
-v
Verbose mode.

man man [options] [section] [title]
Display information from the online reference manuals. man locates and prints the named title from the
designated reference section.

Options
-7, --ascii
Expect a pure ASCII file, and format it for a 7-bit terminal or terminal emulator.
-a, --all
Show all pages matching title.
-b
Leave blank lines in output.
-d, --debug
Display debugging information. Suppress actual printing of manual pages.
-f, --whatis
Same as whatis command.
-k, --apropos
Same as apropos command.
-l, --local-file
Search local files, not system files, for manual pages. If i is given as filename, search standard input.
-m systems, --systems= systems
Search systems' manual pages. systems should be a comma-separated list.
-p preprocessors, --preprocessor= preprocessors
Preprocess manual pages with preprocessors before turning them over to nroff, troff, or groff. Always
runs soelim first.

-r prompt, --prompt= prompt
Set prompt if less is used as pager.
-t, --troff

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Format the manual page with /usr/ bin/ groff -Tgv -mandoc. Implied by -T and -Z.
-u, --update
Perform a consistency check between manual page cache and filesystem.
-w, --where, --location
Print pathnames of entries on standard output.
-D, --default
Reset all options to their defaults.
-L locale, --locale= locale
Assume current locale to be locale; do not consult the setlocale() function.
-M path, --manpath= path
Search for manual pages in path. Ignore -m option.
-Ppager, --pager= pager
Select paging program pager to display the entry.
-T device, --troff-device[= device]
Format groff or troff output for device, such as dvi, latin1, X75, and X100.
-Z, --ditroff
Do not allow postprocessing of manual page after groff has finished formatting it.
Section names
Manual pages are divided into sections, depending on their intended audience:
1
Executable programs or shell commands
2
System calls (functions provided by the kernel)
3
Library calls (functions within system libraries)
4
Special files (usually found in /dev)
5
File formats and conventions (e. g., /etc/ passwd)
6

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Games

7
Macro packages and conventions
8
System administration commands (usually only for a privileged user)
9
Kernel routines (nonstandard)

manpath manpath [options]
Attempt to determine path to manual pages. Check $MANPATH first; if that is not set, consult /etc/ man. conf,
user environment variables, and the current working directory. The manpath command is a symbolic link to
man, but most of the options are ignored for manpath.

Options
-d, --debug
Print debugging information.
-h
Print help message and then exit.

merge merge [options] file1 file2 file3
Perform a three-way file merge. merge incorporates all changes that lead from file2 to file3 and puts the results
into file1. merge is useful for combining separate changes to an original. Suppose file2 is the original, and both
file1 and file3 are modifications of file2. Then merge combines both changes. A conflict occurs if both file1 and
file3 have changes in a common segment of lines. If a conflict is found, merge normally outputs a warning and
puts brackets around the conflict, with lines preceded by <<<<<<< and >>>>>>>. A typical conflict looks like
this:

<<<<<<< file1 relevant lines from file1 ======= relevant lines from file3 >>>>>>> file3

If there are conflicts, the user should edit the result and delete one of the alternatives.
Options
-e
Don't warn about conflicts.
-p
Send results to standard output instead of overwriting file1.
-q
Quiet; do not warn about conflicts.

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-A
Output conflicts using the -A style of diff3. This merges all changes leading from file2 to file3 into file1
and generates the most verbose output.

-E
Output conflict information in a less verbose style than -A; this is the default.
-L label
Specify up to three labels to be used in place of the corresponding filenames in conflict reports. That is:
merge -L x -L y -L z file_ a file_ b file_ cgenerates output that looks as if it came from x, y, and z instead of from file_ a, file_ b, and file_ c.
-V
Print version number.

mesg mesg [option]
Change the ability of other users to send write messages to your terminal. With no options, display the
permission status.

Options
n
Forbid write messages.
y
Allow write messages (the default).

mimencode mimencode [options] [filename] [-o output_ file]
mimencode [options] [filename] [-o output_ file]
Translate to and from MIME encoding formats, the proposed standard for Internet multimedia mail formats. By
default, mimencode reads standard input and sends a base64-encoded version of the input to standard output.

Options
-b
Use the (default) base64 encoding.
-o output_ file
Send output to the named file rather than to standard output.
-p
Translate decoded CRLF sequences into the local newline convention during decoding and do the reverse
during encoding; meaningful only when the default base64 encoding is in effect.

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-q

Use the quoted-printable encoding instead of base64.
-u
Decode the standard input rather than encode it.

mkdir mkdir [options] directories
Create one or more directories. You must have write permission in the parent directory in order to create a
directory. See also rmdir. The default mode of the new directory is 0777, modified by the system or user's
umask.

Options
-m, --mode mode
Set the access mode for new directories. See chmod for an explanation of acceptable formats for mode.
-p, --parents
Create intervening parent directories if they don't exist.
--verbose
Print a message for each directory created.
--help
Print help message and then exit.
--version
Print version number and then exit.
Examples
Create a read-only directory named personal:
mkdir -m 444 personalThe following sequence:
mkdir work; cd work mkdir junk; cd junk mkdir questions; cd ../..

can be accomplished by typing this:
mkdir -p work/ junk/ questions

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mke2fs mke2fs [options] device [blocks]
mkfs. ext2 [options] device [blocks]
System administration command. Format device as a Linux Second Extended Filesystem. You may specify the
number of blocks on the device or allow mke2fs to guess.

Options
-b block-size
Specify block size in bytes.
-c
Scan device for bad blocks before execution.
-f fragment-size
Specify fragment size in bytes.
-i bytes-per-inode
Create an inode for each bytes-per-inode of space. bytes-per-inode must be 1024 or greater; it is 4096 by
default.

-l filename
Consult filename for a list of bad blocks.
-m percentage
Reserve percentage percent of the blocks for use by privileged users.
-q
Quiet mode.
-v
Verbose mode.
-S
Write only superblock and group descriptors; suppress writing of inode table and block and inode
bitmaps. Useful only when attempting to salvage damaged systems.

mkfs mkfs [options] [fs-options] filesys [blocks]
System administration command. Construct a filesystem on a device (such as a hard disk partition). filesys is
either the name of the device or the mountpoint. mkfs is actually a frontend that invokes the appropriate version
of mkfs according to a filesystem type specified by the -t option. For example, a Linux Second Extended
Filesystem uses mkfs. ext2 (which is the same as mke2fs); MS-DOS filesystems use mkfs. msdos. fs-options are
options specific to the filesystem type. blocks is the size of the filesystem in 1024-byte blocks.

Options
-V
Produce verbose output, including all commands executed to create the specific filesystem.

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-t fs-type
Tells mkfs what type of filesystem to construct.
filesystem-specific options
These options must follow generic options and not be combined with them. Most filesystem builders
support these three options:

-c
Check for bad blocks on the device before building the filesystem.
-l file
Read the file file for the list of bad blocks on the device.
-v
Produce verbose ouput.

mkfs. minix mkfs. minix [options] device size
System administration command. Creates a MINIX filesystem. See mkfs.

mklost+ found mklost+ found
System administration command. Create a lost+ found directory in the current working directory. Intended for
Linux Second Extended Filesystems.

mkraid mkraid [options] devices
System administration command. Set up RAID array devices as defined in the /etc/ raidtab configuration file.
mkraid can be used to initialize a new array or upgrade older RAID device arrays for the new kernel.
Initialization will destroy any data on the disk devices used to create the array.

Options
-c file, --configfile file
Use file instead of /etc/ raidtab.
-f, --force
Initialize the devices used to create the RAID array even if they currently have data.
-h, --help
Print a usage message and then exit.
-o, --upgrade
Upgrade an older array to the current kernel's RAID version. Preserve data on the old array.
-V, --version
Print version information and then exit.

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mkswap mkswap [option] device [size]
System administration command. Create swap space on device. You may specify its size in blocks; each block is
a page of about 4KB.

Option
-c
Check for bad blocks before creating the swap space.

modprobe modprobe [options] [modules]
System administration command. With no options, attempt to load the specified module, as well as all modules
on which it depends. If more than one module is specified, attempt to load further modules only if the previous
module failed to load.

Options
-a
Load all listed modules, not just the first one.
-l [pattern]
List all existing modules. This option may be combined with -t to specify a type of module, or you may
include a pattern to search for.

-r
Remove the specified modules, as well as the modules on which they depend.
-t type
Load only a specific type of module. Consult /etc/ conf. modules for the directories in which all modules of
that type reside.

Files
/etc/ conf. modules
Information about modules: which ones depend on others, which directories correspond to particular
types of modules.

/sbin/ insmod, /sbin/ rmmod, /sbin/ depmod
Programs that modprobe relies on.

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more more [options] [files]
Display the named files on a terminal, one screenful at a time. See less for an alternative to more. Some
commands can be preceded by a number.

Options
+num
Begin displaying at line number num.
-num number
Set screen size to number lines.
+/ pattern
Begin displaying two lines before pattern.
-c
Repaint screen from top instead of scrolling.
-d
Display the prompt "Hit space to continue, Del to abort" in response to illegal commands; disable bell.
-f
Count logical rather than screen lines. Useful when long lines wrap past the width of the screen.
-l
Ignore form-feed (Ctrl-L) characters.
-p
Page through the file by clearing each window instead of scrolling. This is sometimes faster.
-r
Force display of control characters, in the form ^x.
-s
Squeeze; display multiple blank lines as one.
-u
Suppress underline characters.
Commands
All commands in more are based on vi commands. An argument can precede many commands.
SPACE
Display next screen of text.
z

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Display next lines of text, and redefine a screenful to lines lines. Default is one screenful.
RETURN
Display next lines of text, and redefine a screenful to lines lines. Default is one line.
d, ^D
Scroll lines of text, and redefine scroll size to lines lines. Default is one line.
q, Q, INTERRUPT
Quit.
s
Skip forward one line of text.
f
Skip forward one screen of text.
b, ^B
Skip backward one screen of text.
'
Return to point where previous search began.
=
Print number of current line.
/pattern
Search for pattern, skipping to numth occurrence if an argument is specified.
n
Repeat last search, skipping to numth occurrence if an argument is specified.
!cmd, :! cmd
Invoke shell and execute cmd in it.
v
Invoke vi editor on the file, at the current line.
^L
Redraw screen.
:n
Skip to next file.
:p

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Skip to previous file.

:f
Print current filename and line number.
.
Reexecute previous command.
Examples
Page through file in "clear" mode, and display prompts:
more -cd fileFormat doc to the screen, removing underlines:
nroff doc | more -uView the manpage for the grep command; begin near the word "BUGS" and compress extra whitespace:
man grep | more +/ BUGS -s

mount mount [options] [special-device] [directory]
System administration command. Mount a file structure. mount announces to the system that a removable file
structure is present on special-device. The file structure is mounted on directory, which must already exist and
should be empty; it then becomes the name of the root of the newly mounted file structure. If mount is invoked
with no arguments, it displays the name of each mounted device, the directory on which it is mounted, whether
the file structure is read-only, and the date it was mounted. Only a privileged user can use the mount command.

Options
-a
Mount all filesystems listed in /etc/ fstab. Note: this is the only option that cannot take a special-device or
node argument.

-f
Fake mount. Go through the motions of checking the device and directory, but do not actually mount the
filesystem.

-n
Do not record the mount in /etc/ mtab.
-o option
Note: this is the only option to mount that requires a special-device or node argument. Qualify the mount
with one of the specified options:

async
Read input and output to the device asynchronously.
auto
Allow mounting with the -a option.

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defaults
Use all options' default values (async, auto, dev, exec, nouser, rw, suid).
dev
Interpret any special devices that exist on the filesystem.
exec
Allow binaries to be executed.
noauto
Do not allow mounting via the -a option.
nodev
Do not interpret any special devices that exist on the filesystem.
noexec
Do not allow the execution of binaries on the filesystem.
nosuid
Do not acknowledge any suid or sgid bits.
nouser
Only privileged users will have access to the filesystem.
remount
Expect the filesystem to have already been mounted, and remount it.
ro
Allow read-only access to the filesystem.
rw
Allow read/ write access to the filesystem.
suid
Acknowledge suid and sgid bits.
sync
Read input and output to the device synchronously.
user
Allow unprivileged users to mount the filesystem. Note that the defaults on such a system will be
nodev, noexec, and nosuid, unless otherwise specified.

check= relaxed| normal| strict
Specify how strictly to regulate the integration of an MS-DOS filesystem when mounting it.

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conv= binary| text| auto
Specify method by which to convert files on MS-DOS and ISO 9660 filesystems.
debug
Turn debugging on for MS-DOS and ext2fs filesystems.
errors= continue| remount| ro| panic
Specify action to take when encountering an error. ext2fs filesystems only.
-r
Mount filesystem read-only.
-t type
Specify the filesystem type. Possible values are: minix, ext, ext2, xiafs, hpfs, msdos, umsdos, vfat,
proc, nfs, iso9660, smbfs, ncpfs, affs, ufs, romfs, sysv, xenix, and coherent. Note that ext and xiafs are
valid only for kernels older than 2.1.21 and that sysv should be used instead of xenix and coherent.

-v
Display mount information verbosely.
-w
Mount filesystem read/ write. This is the default.
Files
/etc/ fstab
List of filesystems to be mounted and options to use when mounting them.
/etc/ mtab
List of filesystems that are currently mounted and the options with which they were mounted.

mountd rpc. mountd [options]
NFS/ NIS command. NFS mount request server. mountd reads the file /etc/ exports to determine which
filesystems are available for mounting by which machines. It also provides information as to what filesystems
are mounted by which clients. See also nfsd.

Options
-d, --debug
Debug mode. Output all debugging information via syslogd.
-f file, --exports-file file

Read the export permissions from file instead of /etc/ exports.
-n, --allow-non-root

Accept even those mount requests that enter via a non-reserved port.
-p, --promiscuous

Accept requests from any host that sends them.
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-r, --re-export

Allow re-exportation of imported filesystems.
-v, --version

Print the version number.
File
/etc/ exports
Information about mount permissions.

mv mv [option] sources target
Move or rename files and directories. The source (first column) and target (second column) determine the result
(third column):

Source Target Result
File name (nonexistent) Rename file to name.
File Existing file Overwrite existing file with source file.
Directory name (nonexistent) Rename directory to name.
Directory Existing directory Move directory to be a subdirectory of existing directory.
One or more files Existing directory Move files to directory.

Options
-b, --backup
Back up files before removing.
-f, --force
Force the move, even if target file exists; suppress messages about restricted access modes.
--help
Print a help message and then exit.
-i, --interactive
Query user before removing files.
-u, --update
Do not remove a file or link if its modification date is the same as or newer than that of its replacement.
-v, --verbose
Print the name of each file before moving it.
--version
Print version information and then exit.
-S suffix, --suffix= suffix
Override the SIMPLE_ BACKUP_ SUFFIX environment variable, which determines the suffix used for

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making simple backup files. If the suffix is not set either way, the default is a tilde (~).

-V value, --version-control= value
Override the VERSION_ CONTROL environment variable, which determines the type of backups made.
The acceptable values for version control are:

t, numbered
Always make numbered backups.
nil, existing
Make numbered backups of files that already have them, simple backups of the others. The
default.

never, simple
Always make simple backups.

named named [options]
TCP/ IP command. Internet domain name server. named is used by resolver libraries to provide access to the
Internet distributed naming database. With no arguments, named reads /etc/ named. boot for any initial data and
listens for queries on a privileged port. See RFC 1034 and RFC 1035 for more details.

There are several named binaries available at different Linux archives, displaying various behaviors. If your
version doesn't behave like the one described here, never fear --it should have come with documentation.

Options
-d debuglevel
Print debugging information. debuglevel is a number indicating the level of messages printed.
-p port
Use port as the port number. Default is 42.
[-b] bootfile
File to use instead of named. boot. The -b is optional and allows you to specify a filename that begins
with a leading dash.

File
/etc/ named. boot
Read when named starts up.

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namei namei [options] pathname [pathname . . .]
Follow a pathname until a terminal point is found (e. g., a file, directory, char device, etc.). If namei finds a
symbolic link, it shows the link and starts following it, indenting the output to show the context. namei prints an
informative message when the maximum number of symbolic links this system can have has been exceeded.

Options
-m
Show the mode bits of each file type in the style of ls; for example: "rwxr-xr-x".
-x
Show mountpoint directories with a D, rather than a d.
File type characters
For each line of output, namei prints the following characters to identify the file types found:
-A
regular file
?
An error of some kind
b
A block device
c
A character device
d
A directory
f:
The pathname namei is currently trying to resolve
l
A symbolic link (both the link and its contents are output)
s
A socket

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netdate netdate [options] [protocol] hostname...
TCP/ IP command. Set the system time according to the time provided by one of the hosts in the list hostname.
netdate tries to ascertain which host is the most reliable source. When run by an unprivileged user, netdate
reports the current time, without attempting to set the system clock. You may specify the protocol --udp (the
default) or tcp --once, or several times for various hosts.

Options
-l time
The most reliable host is chosen from the list by sorting the hosts into groups based on the times they
return when questioned. The first host from the largest group is then polled a second time. The
differences between its time and the local host's time on each poll are recorded. These two differences are
then compared. If the gap between them is greater than time (the default is five seconds), the host is
rejected as inaccurate.

-v
Display the groups into which hosts are sorted.

netstat netstat [options]
TCP/ IP command. Show network status. For all active sockets, print the protocol, the number of bytes waiting to
be received, the number of bytes to be sent, the port number, the remote address and port, and the state of the
socket.

Options
-a
Show the state of all sockets, not just active ones.
-c
Display information continuously, refreshing once every second.
-i
Include statistics for network devices.
-n
Show network addresses as numbers.
-o
Include additional information such as username.
-r
Show routing tables.
-t
List only TCP sockets.
-u
List only UDP sockets.

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-v
Print the version number and exit.
-w
List only raw sockets.
-x
List only Unix domain sockets.

newgrp newgrp [group]
Change user's group identification to the specified group. If no group is specified, change to the user's login
group. The new group is then used for checking permissions.

newusers newusers file
System administration command. Create or update system users from entries in file. Each line in file has the
same format as an entry in /etc/ passwd, except passwords are unencrypted, and group IDs can be given as a
name or number. During an update, the password age field is ignored if the user already exists in the /etc/ shadow
password file. If a group name or ID does not already exist, it will be created. If a home directory does not exist,
it will be created.

nfsd rpc. nfsd [options]
System administration command. Daemon that starts the NFS server daemons that handle client filesystem
requests. These daemons are user-level processes. The options are exactly the same as in mountd.

nice nice [option] [command [arguments]]
Execute a command (with its arguments) with lower priority (i. e., be "nice" to other users). With no arguments,
nice prints the default scheduling priority (niceness). If nice is a child process, it prints the parent process's
scheduling priority. Niceness has a range of -20 (highest priority) to 19 (lowest priority).

Options
--help
Print a help message and then exit.
-n adjustment, -adjustment, --adjustment= adjustment
Run command with niceness incremented by adjustment (1-19); default is 10. A privileged user can raise
priority by specifying a negative adjustment (e. g., -5).

--version
Print version information and then exit.

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nm nm [options] [objfiles]
Print the symbol table (name list) in alphabetical order for one or more object files. If no object files are
specified, perform operations on a. out. Output includes each symbol's value, type, size, name, and so on. A key
letter categorizing the symbol can also be displayed. If no object file is given, use a. out.

Options
-a, --debug-syms
Print debugger symbols.
-f format
Specify output format (bsd, sysv, or posix). Default is bsd.
-g, --extern-only
Print external symbols only.
-n, -v, --numeric-sort
Sort the external symbols by address.
-p, --no-sort
Don't sort the symbols at all.
-r, --reverse-sort
Sort in reverse, alphabetically or numerically.
--size-sort
Sort by size.
-u, --undefined-only
Report only the undefined symbols.
-A, -o, -print-file-name
Print input filenames before each symbol.
-C, --demangle
Translate low-level symbol names into readable versions.
-D, --dynamic
Print dynamic, not normal, symbols. Useful only when working with dynamic objects (some kinds of
shared libraries, for example).

-P, --portability
Same as -f posix.
-V, --version
Print nm's version number on standard error.

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nohup nohup command [arguments]
Run the named command with its optional command arguments, continuing to run it even after you log out
(make command immune to hangups; i. e., no hangup). TTY output is appended to the file nohup. out by default.
Modern shells preserve background commands by default; this command is necessary only in the original
Bourne shell.

nslookup nslookup [-option...] [host_ to_ find | -[server ]]
TCP/ IP command. Query Internet domain name servers. nslookup has two modes: interactive and
noninteractive. Interactive mode allows the user to query name servers for information about various hosts and
domains or to print a list of hosts in a domain. It is entered either when no arguments are given (default name
server will be used) or when the first argument is a hyphen and the second argument is the hostname or Internet
address of a name server. Noninteractive mode is used to print just the name and requested information for a
host or domain. It is used when the name of the host to be looked up is given as the first argument. Any of the
keyword= value pairs listed under the interactive set command can be used as an option on the command line by
prefacing the keyword with a -. The optional second argument specifies a name server.

Options
All of the options under the set interactive command can be entered on the command line, with the syntax -keyword[=
value].

Interactive commands
exit
Exit nslookup.
finger [name] [>|>> filename]
Connect with finger server on current host, optionally creating or appending to filename.
help, ?
Print a brief summary of commands.
host [server]
Look up information for host using the current default server or using server if specified.
ls -[ ahd] domain [>|>> filename]
List information available for domain, optionally creating or appending to filename. The -a option lists
aliases of hosts in the domain. -h lists CPU and operating system information for the domain. -d lists all
contents of a zone transfer.

lserver domain
Change the default server to domain. Use the initial server to look up information about domain.
root
Change default server to the server for the root of the domain namespace.
server domain
Change the default server to domain. Use the current default server to look up information about domain.

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set keyword[= value]

Change state information affecting the lookups. Valid keywords are:
all
Print the current values of the frequently used options to set.
class= name
Set query class to IN (Internet), CHAOS, HESIOD, or ANY. Default is IN.
domain= name
Change default domain name to name.
[no] debug
Turn debugging mode on or off.
[no] d2
Turn exhaustive debugging mode on or off.
[no] defname
Append default domain name to every lookup.
[no] ignoretc
Ignore truncate error.
[no] recurse
Tell name server to query or not query other servers if it does not have the information.
[no] search
With defname, search for each name in parent domains of current domain.
[no] vc
Always use a virtual circuit when sending requests to the server.
port= port
Connect to name server using port.
querytype= value
See type= value.
retry= number
Set number of retries to number.
root= host
Change name of root server to host.
srchlist= domain
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Set search list to domain.
timeout= number
Change timeout interval for waiting for a reply to number seconds.
type= value
Change type of information returned from a query to one of:

A Host's Internet address
ANY Any available information
CNAME Canonical name for an alias
HINFO Host CPU and operating system
type
MD Mail destination
MG Mail group member
MINFO Mailbox or mail list
information
MR Mail rename domain name
MX Mail exchanger
NS Nameserver for the named zone
PTR Hostname or pointer to other
information
SOA Domain start-of-authority
TXT Text information
UINFO User information
WKS Supported well-known services
view filename

Sort and list output of previous ls command( s) with more.

passwd passwd [user]
Create or change a password associated with a user name. Only the owner or a privileged user may change a
password. Owners need not specify their user name.

paste paste [options] files
Merge corresponding lines of one or more files into tab-separated vertical columns. See also cut, join, and pr.
Options
-Replace
a filename with the standard input.
-dchar, --delimiters= char
Separate columns with char instead of a tab. Note: you can separate columns with different characters by
supplying more than one char.

--help

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Print a help message and then exit.
--version
Print version information and then exit.
-s, --serial
Merge lines from one file at a time.
Examples
Create a three-column file from files x, y, and z:
paste x y z > fileList users in two columns:
who | paste --Mergeeach pair of lines into one line:
paste -s -d"\ t\ n" list

patch patch [options] [original [patchfile]]
Apply the patches specified in patchfile to original. Replace the original with the new, patched version; move
the original to original. orig or original~.

Options
+ [options] [original2]
Apply patches again, with different options or a different original file.
-b, --backup
Back up the original file.
-z suffix, --suffix= suffix
Back up the original file in original. suffix.
-B prefix, --prefix= prefix
Prepend prefix to the backup filename.
-c, --context
Interpret patchfile as a context diff.
-d dir, --directory= dir
cd to directory before beginning patch operations.
-D string, --ifdef= string
Mark all changes with:

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#ifdef string #endif

-e, --ed
Treat the contents of patchfile as ed commands.
-E, --remove-empty-files
If patch creates any empty files, delete them.
-f, --force
Force all changes, even those that look incorrect. Skip patches if the original file does not exist; force
patches for files with the wrong version specified; assume patches are never reversed.

-i file, --input= file
Read patch from file instead of stdin.
-t, --batch
Skip patches if the original file does not exist.
-F num, --fuzz= num
Specify the maximum number of lines that may be ignored (fuzzed over) when deciding where to install a
hunk of code. The default is 2. Meaningful only with context diffs.

-l, --ignore-whitespace
Ignore whitespace while pattern matching.
-n, --normal
Interpret patch file as a normal diff.
-N, --forward
Ignore patches that appear to be reversed or to have already been applied.
-o file, --output= file
Print output to file.
-p[ num], --strip[= num]
Specify how much of preceding pathname to strip. A num of 0 strips everything, leaving just the
filename. 1 strips the leading /; each higher number after that strips another directory from the left.

-r file, --reject-file= file
Place rejects (hunks of the patch file that patch fails to place within the original file) in file. Default is
original. rej.

-R, --reverse
Do a reverse patch: attempt to undo the damage done by patching with the old and new files reversed.
-s, --silent, --quiet

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Suppress commentary.
-u, --unified
Interpret patch file as a unified context diff.
-V method, --version-control= method
Specify method for creating backup files (overridden by -B):
t, numbered
Make numbered backups.
nil, existing
Back up files according to preexisting backup schemes, with simple backups as the default. This is
patch's default behavior.

never, simple
Make simple backups.
Environment variables
TMPDIR
Specify the directory for temporary files, /tmp by default.
SIMPLE_ BACKUP_ SUFFIX
Suffix to append to backup files instead of .orig or ~.
VERSION_ CONTROL
Specify what method to use in naming backups (see -V).

pathchk pathchk [ option ] filenames
Determine validity and portability of filenames. Specifically, determine if all directories within the path are
searchable and if the length of the filenames is acceptable.

Options
-p, --portability
Check portability for all POSIX systems.
--help
Print a help message and then exit.
--version
Print version information and then exit.

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pcnfsd /usr/ sbin/ rpc. pcnfsd
NFS/ NIS command. NFS authentication and print request server. pcnfsd is an RPC server that supports ONC
clients on PC systems. pcnfsd reads the configuration file /etc/ pcnfsd. conf, if present, then services RPC requests
directed to program number 150001. This current release of the pcnfsd daemon (as of this printing) supports
both Version 1 and Version 2 of the pcnfsd protocol. Requests serviced by pcnfsd fall into three categories:
authentication, printing, and other. Only the authentication and printing services have administrative
significance.

Authentication
When pcnfsd receives a PCNFSD_ AUTH or PCNFSD2_ AUTH request, it will log in the user by validating the
username and password, returning the corresponding user ID, group IDs, home directory, and umask. At this
time, pcnfsd will also append a record to the wtmp database. If you do not want to record PC logins in this way,
add the line:

wtmp offto the /etc/ pcnfsd. conf file.
Printing
pcnfsd supports a printing model based on the use of NFS to transfer the actual print data from the client to the
server. The client system issues a PCNFSD_ PR_ INIT or PCNFSD2_ PR_ INIT request, and the server returns the
path to a spool directory that the client may use and that is exported by NFS. pcnfsd creates a subdirectory for
each of its clients; the parent directory is normally /usr/ spool/ pcnfs and the subdirectory is the hostname of the
client system. If you want to use a different parent directory, add the line:

spooldir pathto the /etc/ pcnfsd. conf file. Once a client has mounted the spool directory and has transferred print data to a file
in this directory, pcnfsd will issue a PCNFSD_ PR_ START or PCNFSD2_ PR_ START request. pcnfsd
constructs a command based on the printing services of the server operating system and executes the command
using the identity of the PC user. Every print request includes the name of the printer to be used. pcnfsd
interprets a printer as either a destination serviced by the system print spooler or as a virtual printer. Virtual
printers are defined by the following line in the /etc/ pcnfsd. conf file:

printer name alias-for commandwhere name is the name of the printer you want to define, alias-for is the name of a real printer that corresponds
to this printer, and command is a command that will be executed whenever a file is printed on name.

perl perl
A powerful text-processing language that combines many of the most useful features of shell programs, C, awk,
and sed, as well as adding extended features of its own. For more information, see Learning Perl by Randal L.
Schwartz and Programming Perl, 2d ed., by Larry Wall, Tom Christiansen, and Randal L. Schwartz.

pidof pidof [options] programs
Display the process IDs of the listed program or programs. pidof is actually a symbolic link to killall5.
Options
-o pids
Omit all processes with the specified process ID. You may list several process IDs.
-s

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Return a single process ID.

-x
Also return process IDs of shells running the named scripts.

ping ping [options] host
System administration command. Confirm that a remote host is online and responding. ping is intended for use
in network testing, measurement, and management. Because of the load it can impose on the network, it is
unwise to use ping during normal operations or from automated scripts.

Options
-c count
Stop after sending (and receiving) count ECHO_ RESPONSE packets.
-d
Set SO_ DEBUG option on socket being used.
-f
Flood ping-output packets as fast as they come back or 100 times per second, whichever is more. This
can be very hard on a network and should be used with caution; only a privileged user may use this
option.

-i wait
Wait wait seconds between sending each packet. Default is to wait 1 second between each packet. This
option is incompatible with the -f option.

-l preload
Send preload number of packets as fast as possible before falling into normal mode of behavior.
-n
Numeric output only. No attempt will be made to look up symbolic names for host addresses.
-p digits
Specify up to 16 pad bytes to fill out packet sent. This is useful for diagnosing data-dependent problems
in a network. digits are in hex. For example, -p ff will cause the sent packet to be filled with all 1s.

-q
Quiet output --nothing is displayed except the summary lines at startup time and when finished.
-r
Bypass the normal routing tables and send directly to a host on an attached network.
-s packetsize
Specify number of data bytes to be sent. Default is 56, which translates into 64 ICMP data bytes when
combined with the 8 bytes of ICMP header data.

-v

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Verbose --list ICMP packets received other than ECHO_ RESPONSE.
-R
Set the IP record route option, which will store the route of the packet inside the IP header. The contents
of the record route will be printed if the -v option is given, and will be set on return packets if the target
host preserves the record route option across echoes or the -l option is given.

pop2d in. pop2d
System administration command. Allow users to connect to port 109 and request the contents of their mailbox in
/var/ spool/ mail. pop2d requires a username and password before providing mail and can serve individual
messages. See also pop3d.

Commands
Each command must be entered on a separate line.
HELO
Prompt for username and password.
FOLD

Open /var/ spool/ mail/$ USER.
HOST

Open /var/ spool/ pop/$ USER.
READ

Read a message.
RETR

Retrieve a message.
ACKS

Save the last message retrieved and move to next message.
ACKD

Delete the last message retrieved and move to next message.
NACK

Save the last message retrieved and expect to resend it.
QUIT

Exit.

pop3d in. pop3d
System administration command. pop3d is a more recent version of pop2d. It behaves similarly but accepts a
slightly different list of commands.

Commands
USER
Prompt for name.
PASS

Prompt for password.

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STAT

Display the number of messages in the mailbox and its total size.
LIST

Display individual messages' sizes.
DELE

Delete a message.
NOOP

Perform a null operation.
LAST

Print the number of the most recently received message that has been read.
RSET

Reset: clear all deletion marks.
TOP

Print the first part of a message.
QUIT

Exit.

portmap rpc. portmap [option]
NFS/ NIS command. RPC program number to IP port mapper. portmap is a server that converts RPC program
numbers to IP port numbers. It must be running in order to make RPC calls. When an RPC server is started, it
tells portmap what port number it is listening to and what RPC program numbers it is prepared to serve. When a
client wishes to make an RPC call to a given program number, it first contacts portmap on the server machine to
determine the port number where RPC packets should be sent. portmap must be the first RPC server started.

Option
-d
Run portmap in debugging mode. Does not allow portmap to run as a daemon.

powerd powerd device
System administration command. Monitor the connection to an uninterruptible power supply, which the user
must specify via device. When power goes low, signal init to run its powerwait and powerfail entries; when full
power is restored, signal init to run its powerokwait entries.

pppd pppd [options] [tty] [speed]
System administration command. PPP stands for the Point-to-Point Protocol; it allows datagram transmission
over a serial connection. pppd attempts to configure tty for PPP (searching in /dev) or, by default, the controlling
terminal. You can also specify a baud rate of speed.

Options
asyncmap map
Specify which control characters cannot pass over the line. map should be a 32-bit hex number, where
each bit represents a character to escape. For example, bit 00000001 represents the character 0x00; bit
80000000 represents the character 0x1f or _. You may specify multiple characters.

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auth

Require self-authentication by peers before allowing packets to move.
connect command
Connect as specified by command, which may be a binary or shell command.
debug, -d
Increment the debugging level.
defaultroute
Add a new default route in which the peer is the gateway. When the connection shuts down, remove the
route.

-detach
Operate in the foreground. By default, pppd forks and operates in the background.
disconnect command
Close the connection as specified by command, which may be a binary or shell command.
domain d
Specify a domain name of d.
escape character-list
Escape all characters in character-list, which should be a comma-separated list of hex numbers. You
cannot escape 0x20-0x3f or 0x5e.

file file
Consult file for options.
lock
Allow only pppd to access the device.
mru bytes
Refuse packets of more than bytes bytes.
name name
Specify a machine name for the local system.
netmask mask
Specify netmask (for example, 255.255.255.0).
passive, -p
Do not exit if peer does not respond to attempts to initiate a connection. Instead, wait for a valid packet
from the peer.

silent

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Send no packets until after receiving one.

[local_ IP_ address]:[ remote_ IP_ address]
Specify the local and/ or remote interface IP addresses, as hostnames or numeric addresses.
Files
/var/ run/ pppn. pid
pppd's process ID. The n in pppn. pid is the number of the PPP interface unit corresponding to this pppd
process.

/etc/ ppp/ ip-up
Binary or script to be executed when the PPP link becomes active.
/etc/ ppp/ ip-down
Binary or script to be executed when the PPP link goes down.
/etc/ ppp/ pap-secrets
Contains usernames, passwords, and IP addresses for use in PAP authentication.
/etc/ ppp/ options
System defaults. Options in this file are set before the command-line options.
~/. ppprc
The user's default options. These are read before command-line options but after the system defaults.
/etc/ ppp/ options. ttyname
Name of the default serial port.

pr pr [files]
Convert a text file or files to a paginated, columned version, with headers. If -is provided as the filename, read
from standard input.

Options
+beg_ pag[: end-pag], --pages=[ beg_ pag[: end-pag]
Begin printing on page beg_ pag and end on end-pag if specified.
-num_ cols, --columns= num_ cols
Print in num_ cols number of columns, balancing the number of lines in the columns on each page.
-a, --across
Print columns horizontally, not vertically.
-c, --show-control-chars
Convert control characters to hat notation (such as ^C) and other unprintable characters to octal
backslash format.

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-d, --double-space
Double space.
-e[ tab-char[ width]], --expand-tabs=[ tab-char[ width]]
Convert tabs (or tab-chars) to spaces. If width is specified, convert tabs to width characters (default is 8).
-f, -F, --form-feed
Separate pages with form feeds, not newlines.
-h header, --header= header
Use header for the header instead of the filename.
-i[ out-tab-char[ out-tab-width]], --output-tabs[= out-tab-char[ out-tab-width]]
Replace spaces with tabs on output. Can specify alternative tab character (default is tab) and width
(default is 8).

-J, --join-lines
Merge full lines; ignore -W if set.
-l lines, --length= lines
Set page length to lines (default 66). If lines is less than 10, omit headers and footers.
-m, --merge
Print all files, one file per column.
-n[ delimiter[ digits]], --number-lines[= delimiter[ digits]]
Number columns, or, with the -m option, number lines. Append delimiter to each number (default is a
tab) and limit the size of numbers to digits (default is 5).

-o width, --indent= width
Set left margin to width.
-r, --no-file-warnings
Continue silently when unable to open an input file.
-s[ delimiter], --separator[= delimiter]
Separate columns with delimiter (default is a tab) instead of spaces.
-S[ string], --sep-string[= string]
Separate columns with string. Default is a tab with -J and a space otherwise.
-t, --omit-header
Suppress headers, footers, and fills at end of pages.
-T, --omit-pagination

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Like -t but also suppress form feeds.

-v, --show-non-printing
Convert unprintable characters to octal backslash format.
-w page_ width, --width= page_ width
Set the page width to page_ width characters for multi-column output. Default is 72.
-W page_ width, --page-width= page_ width
Set the page width to always be page_ width characters. Default is 72.
--help
Print a help message and then exit.
--version
Print version information and then exit.

praliases praliases [option]
System administration command. praliases prints the current sendmail mail aliases. (Usually defined in the
/etc/ aliases or /etc/ aliases. db file.)

Option
-f file
Read the aliases from the specified file instead of sendmail's default alias files.

printenv printenv [variables]
Print values of all environment variables or, optionally, only the specified variables.

printf printf formats [strings]
Print strings using the specified formats. formats can be ordinary text characters, C-language escape characters,
or more commonly, a set of conversion arguments listed here.

Arguments
%s
Print the next string.
%n$ s
Print the nth string.
%[-] m[. n] s
Print the next string, using a field that is m characters wide. Optionally, limit the field to print only the
first n characters of string. Strings are right-adjusted unless the left-adjustment flag, -, is specified.

Examples

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printf '% s %s\ n' "My files are in" $HOME printf '%-25.15s %s\ n' "My files are in" $HOME

ps ps [options]
Report on active processes. Note that you do not need to include a -before options. In options, list arguments
should either be separated by commas or be put in double quotes. In comparing the amount of output produced,
note that e prints more than a and l prints more than f.

Options
pids
Include only specified processes, which are given in a comma-delimited list.
a
List all processes.
c
Consult task_ struct for command name.
e
Include environment.
f
"Forest" family tree format.
h
Suppress header.
j
Jobs format.
l
Produce a long listing.
m
Memory format.
n
Print user IDs and WCHAN numerically.
r
Exclude processes that are not running.
s
Signal format.
--sortdelimiter[+|-] key[,[+|-] key[,...]]

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Similar to O, but designed to protect multiletter sort keys. See the later list, "Sort keys".
ttty
Display only processes running on tty.
u
Include username and start time.
v
vm format.
w
Wide format. Don't truncate long lines.
x
Include processes without an associated terminal.
O[+|-] key[,[+|-] key[,...]]
Sort processes. (See the following list, "Sort keys.")
+
Return key to default direction.
-Reverse
default direction on key.
S
Include child processes' CPU time and page faults.
Sort keys
c, cmd
Name of executable.
C, cmdline
Whole command line.
f, flags
Flags.
g, pgrp
Group ID of process.
G, tpgid
Group ID of associated tty.

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j, cutime

Cumulative user time.
J, cstime
Cumulative system time.
k, utime
User time.
K, stime
System time.
m, min_ flt
Number of minor page faults.
M, maj_ flt
Amount of major page faults.
n, cmin_ flt
Total minor page faults.
N, cmaj_ flt
Total major page faults.
o, session
Session ID.
p, pid
Process ID.
P, ppid
Parent's process ID.
r, rss
Resident set size.
R, resident
Resident pages.
s, size
Kilobytes of memory used.
S, share
Number of shared pages.

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t, tty

tty.
T, start_ time
Process's start time.
U, uid
User ID.
u, user
User's name.
v, vsize
Bytes of VM used.
y, priority
Kernel's scheduling priority.
Fields
PRI
Process's scheduling priority. A higher number indicates lower priority.
NI
Process's nice value. A higher number indicates less CPU time.
SIZE
Size of virtual image.
RSS
Resident set size (amount of physical memory), in kilobytes.
WCHAN
Kernel function in which process resides.
STAT
Status:
R
Runnable
T
Stopped
D
Asleep and not interruptible
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S
Asleep
Z
Zombie
W
No resident pages (second field)
N
Positive nice value (third field)
TT
Associated tty.
PAGEIN
Number of major page faults.
TRS
Size of resident text.
SWAP
Amount of swap used, in kilobytes.
SHARE
Shared memory.

psupdate psupdate [mapfile]
System administration command. Update the psupdate database (on some systems /boot/ psupdate; on others,
/etc/ psdatabase), which contains information about the kernel image system map file. If no mapfile is specified,
psupdate uses the default (which is either /usr/ src/ linux/ vmlinux or /usr/ src/ linux/ tools/ zSystem, depending on
the distribution).

pwck pwck [option] [files]
System administration command. Remove corrupt or duplicate entries in the /etc/ passwd and /etc/ shadow files.
pwck will prompt for a "yes" or "no" before deleting entries. If the user replies "no," the program will exit.
Alternate passwd and shadow files can be checked. If correctable errors are found, the user will be encouraged to
run the usermod command.

Option
-n
Noninteractive mode. Don't prompt for input, and delete no entries. Return appropriate exit status.
Exit status

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0

Success.
1
Syntax error.
2
One or more bad password entries found.
3
Could not open password files.
4
Could not lock password files.
5
Could not write password files.

pwconv pwconv
pwunconv
System administration command. Convert unshadowed entries in /etc/ passwd into shadowed entries in the
/etc/ shadow file. Replace the encrypted password in /etc/ password with an x. Shadowing passwords keeps them
safe from password cracking programs. pwconv creates additional expiration information for the /etc/ shadow
file from entries in your /etc/ login. defs file. If you add new entries to the /etc/ passwd file, you can run pwconv
again to transfer the new information to /etc/ shadow. Already shadowed entries are ignored. pwunconv restores
the encrypted passwords to your /etc/ passwd file and removes the /etc/ shadow file. Some expiration information
is lost in the conversion.

pwd pwd
Print the full pathname of the current working directory. See also the dirs shell command, built in to both bash
and csh/ tcsh.

quota quota [options] [user| group]
Display disk usage and total space allowed for a designated user or group. With no argument, the quota for the
current user is displayed. This command reports quotas for all filesystems listed in /etc/ fstab.

Options
-g
Given with a user argument, display the quotas for the groups of which the user is a member, instead of
the user's quotas.
-q

Display information only for filesystems in which the user is over quota.
-u

The default behavior. When used with -g, display both user and group quota information.
-v

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Display quotas for filesystems even if no storage is currently allocated.

raidstart raidstart [options] [devices]
raidstop [options] [devices]
System administration command. Start or stop RAID devices as defined in the RAID configuration file,
/etc/ raidtab. If option -a (or --all) is used, no devices need to be given; the command will be applied to all the
devices defined in the configuration file.

Options
-a, --all
Apply command to all devices defined in the RAID configuration file.
-c file, --configfile file
Use file instead of /etc/ raidtab.
-h, --help
Print usage message and exit.
-V, --version
Print version and exit.

ramsize ramsize [option] [image [size [offset]]]
System administration command. If no options are specified, print usage information for the RAM disk. The pair
of bytes at offset 504 in the kernel image normally specify the RAM size; with a kernel image argument, print
the information found at that offset. To change that information, specify a new size (in kilobytes). You may also
specify a different offset. Note that rdev -r is the same as ramsize.

Option
-o offset
Same as specifying an offset as an argument.

ranlib ranlib filename
Generate an index for archive file filename. Same as running ar -s.

rarp rarp [options]
System administration command. Administer the Reverse Address Resolution Protocol table (usually
/proc/ net/ rarp).

Options
-a [hostname]
Show all entries. If hostname is specified, show only the entries relevant to hostname, which may be a
list.

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-d hostname

Remove the entries relevant to hostname, which may be a list.
-s hostname hw_ addr
Add a new entry for hostname, with the hardware address hw_ addr.
-t type
Check only for type entries when consulting or changing the table. type may be ether (the default) or
ax25.

-v
Verbose mode.

rcp rcp [options] file1 file2
rcp [options] file ... directory
Copy files between two machines. Each file or directory is either a remote filename of the form
rname@ rhost: path or a local filename.

Options
-k
Attempt to get tickets for remote host; query krb_ realmofhost to determine realm.
-p
Preserve modification times and modes of the source files.
-r
If any of the source files are directories, rcp copies each subtree rooted at that name. The destination
must be a directory.

-x
Turns on DES encryption for all data passed by rcp.

rdate rdate [options] [host...]
TCP/ IP command. Retrieve the date and time from a host or hosts on the network and optionally set the local
system time.

Options
-p
Print the retrieved dates.
-s
Set the local system time from the host; must be specified by root.

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rdev rdev [options] [image [value [offset]]]
System administration command. If no arguments are specified, display a line, in /etc/ mtab syntax, that describes
the root filesystem. Otherwise, change the values of the bytes in the kernel image that describe the RAM disk
size (by default located at decimal byte offset 504 in the kernel), VGA mode (default 506), and root device
(default 508). You must specify the kernel image to change and may specify a new value and a different offset.

Options
-o offset
Same as specifying an offset as an argument. The offset is given in decimal.
-r
Behave like ramsize.
-s
Behave like swapdev.
-v
Behave like vidmode.
-R
Behave like rootflags.

rdist rdist [options] [names]
System administration command. Remote file distribution client program. rdist maintains identical copies of
files over multiple hosts. It reads commands from a file named distfile to direct the updating of files and/ or
directories. An alternative distfile can be specified with the -f option or the -c option.

Options
-a num
Do not update filesystems with fewer than num bytes free.
-c name [login@] host[: dest]
Interpret the arguments as a small distfile, where login is the user to log in as, host is the destination host,
name is the local file to transfer, and dest is the remote name where the file should be installed.

-d var= value
Define var to have value. This option defines or overrides variable definitions in the distfile. Set the
variable var to value.

-f file
Read input from file (by default, distfile). If file is -, read from standard input.
-l options
Specify logging options on the local machine.
-m machine

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Update only machine. May be specified multiple times for multiple machines.
-n
Suppress normal execution. Instead, print the commands that would have been executed.
-ooptions
Specify one or more options, which must be comma-separated.
chknfs
Suppress operations on files that reside on NFS filesystems.
chkreadonly
Check filesystem to be sure it is not read-only before attempting to perform updates.
chksym
Do not update files that exist on the local host but are symbolic links on the remote host.
compare
Compare files; use this comparison rather than age as the criteria for determining which files
should be updated.

follow
Interpret symbolic links, copying the file to which the link points instead of creating a link on the
remote machine.

ignlnks
Ignore links that appear to be unresolvable.
nochkgroup
Do not update a file's group ownership unless the entire file needs updating.
nochkmode
Do not update file mode unless the entire file needs updating.
nochkowner
Do not update file ownership unless the entire file needs updating.
nodescend
Suppress recursive descent into directories.
noexec
Suppress rdist of executables that are in a. out format.
numchkgroup
Check group ownership by group ID instead of by name.

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numchkowner

Check file ownership by user ID instead of by name.
quiet
Quiet mode; do not print commands as they execute.
remove
Remove files that exist on the remote host but not the local host.
savetargets
Save updated files in name. old.
verify
Print a list of all files on the remote machine that are out of date, but do not update them.
whole
Preserve directory structure by creating subdirectories on the remote machine. For example, if you
rdist the file /foo/ bar into the directory /baz, it would produce the file /baz/ foo/ bar, instead of the
default, /baz/ bar.

younger
Do not update files that are younger than the master files.
-p path
Specify the path to search for rdistd on the remote machine.
-t seconds
Specify the timeout period (default 900 seconds) after which rdist will sever the connection if the remote
server has not yet responded.

-A num
Specify the minimum number of inodes that rdist requires.
-D
Debugging mode.
-F
Execute all commands sequentially, without forking.
-L options
Specify logging options on the remote machine.
-M num
Do not allow more than num child rdist processes to run simultaneously. Default is 4.
-P path

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Specify path to rsh on the local machine.

rdistd rdistd options
System administration command. Start the rdist server. Note that you must specify the -S option, unless you are
simply querying for version information with -V.

Options
-D
Debugging mode.
-S
Start the server.
-V
Display the version number and exit immediately.

reboot reboot [options]
System administration command. Close out filesystems, shut down the system, then reboot the system. Because
this command immediately stops all processes, it should be run only in single-user mode. If the system is not in
runlevel 0 or 6, reboot calls shutdown -nf.

Options
-d
Suppress writing to /var/ log/ wtmp.
-f
Call reboot even when shutdown would normally be called.
-n
Suppress normal call to sync.
-w
Suppress normal execution; simply write to /var/ log/ wtmp.

renice renice [priority] [options] [target]
Control the scheduling priority of various processes as they run. May be applied to a process, process group, or
user (target). A privileged user may alter the priority of other users' processes. priority must, for ordinary users,
lie between 0 and the environment variable PRIO_ MAX (normally 20), with a higher number indicating
increased niceness. A privileged user may set a negative priority, as low as PRIO_ MIN, to speed up processes.

Options
+num
Specify number by which to increase current priority of process, rather than an absolute priority number.
-num
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Specify number by which to decrease current priority of process, rather than an absolute priority number.
-g
Interpret target parameters as process group IDs.
-p
Interpret target parameters as process IDs (default).
-u
Interpret target parameters as usernames.

reset reset
Clear screen (reset terminal).

rev rev [file]
Reverse the lines of a file onto standard output. The order of characters on each line is also reversed. If no file is
specified, rev reads from standard input.

rexecd rexecd command-line
TCP/ IP command. Server for the rexec routine, providing remote execution facilities with authentication based
on usernames and passwords. rexecd is started by inetd and must have an entry in inetd's configuration file,
/etc/ inetd. conf. When rexecd receives a service request, the following protocol is initiated:

1. The server reads characters from the socket up to a null byte. The resulting string is interpreted as an
ASCII number, base 10.

2. If the number received in step 1 is nonzero, it is interpreted as the port number of a secondary stream to
be used for stderr. A second connection is then created to the specified port on the client's machine.

3. A null-terminated username of at most 16 characters is retrieved on the initial socket.
4. A null-terminated, unencrypted password of at most 16 characters is retrieved on the initial socket.
5. A null-terminated command to be passed to a shell is retrieved on the initial socket. The length of the
command is limited by the upper bound on the size of the system's argument list.

6. rexecd then validates the user, as is done at login time and, if the authentication was successful, changes
to the user's home directory and establishes the user and group protections of the user.

7. A null byte is returned on the connection associated with stderr, and the command line is passed to the
normal login shell of the user. The shell inherits the network connections established by rexecd.

Diagnostics
Username too long
Name is longer than 16 characters.
Password too long
Password is longer than 16 characters.

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Command too long

Command passed is too long.
Login incorrect
No password file entry for the username exists.
Password incorrect
Wrong password was supplied.
No remote directory
chdir to home directory failed.
Try again
fork by server failed.
<shellname>:...
fork by server failed. User's login shell could not be started.

rlogin rlogin rhost [options]
Remote login. rlogin connects the terminal on the current local host system to the remote host system rhost. The
remote terminal type is the same as your local terminal type. The terminal or window size is also copied to the
remote system if the server supports it.

Options
-8
Allow an 8-bit input data path at all times.
-ec
Specify escape character c (default is ~).
-d
Debugging mode.
-k
Attempt to get tickets from remote host, requesting them in the realm as determined by krb_ realm-ofhost.

-l username
Specify a different username for the remote login. Default is the same as your local username.
-x
Turns on DES encryption for all data passed via the rlogin session.
-E

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Do not interpret any character as an escape character.

-K
Suppress all Kerberos authentication.
-L
Allow rlogin session to be run without any output postprocessing (i. e., run in litout mode).

rlogind rlogind [options]
TCP/ IP command. Server for the rlogin program, providing a remote login facility, with authentication based on
privileged port numbers from trusted hosts. rlogind is invoked by inetd when a remote login connection is
requested and executes the following protocol:

l The server checks the client's source port. If the port is not in the range 0-023, the server aborts the
connection.

l The server checks the client's source address and requests the corresponding hostname. If the hostname
cannot be determined, the dot-notation representation of the host address is used.

The login process propagates the client terminal's baud rate and terminal type, as found in the environment
variable, TERM.

Options
-a
Verify hostname.
-l
Do not authenticate hosts via a nonroot .rhosts file.
-n
Suppress keep-alive messages.

rm rm [options] files
Delete one or more files. To remove a file, you must have write permission in the directory that contains the file,
but you need not have permission on the file itself. If you do not have write permission on the file, you will be
prompted (y or n) to override.

Options
-d, --directory
Remove directories, even if they are not empty. Available only to a privileged user.
-f, --force
Remove write-protected files without prompting.
--help
Print a help message and then exit.

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-i, --interactive

Prompt for y (remove the file) or n (do not remove the file).
-r, -R, --recursive
If file is a directory, remove the entire directory and all its contents, including subdirectories. Be
forewarned: use of this option can be dangerous.

-v, --verbose
Turn on verbose mode. (rm prints the name of each file before removing it.)
--version
Print version information and then exit.
--
Mark the end of options. Use this when you need to supply a filename beginning with -.

rmail rmail user...
TCP/ IP command. Handle remote mail received via uucp, collapsing From lines in the form generated by mail
into a single line of the form return-path! sender and passing the processed mail onto sendmail. rmail is
explicitly designed for use with uucp and sendmail.

rmdir rmdir [options] directories
Delete the named directories (not the contents). directories are deleted from the parent directory and must be
empty (if not, rm -r can be used instead). See also mkdir.

Options
--help
Print a help message and then exit.
--ignore-fail-on-non-empty
Ignore failure to remove directories that are not empty.
-p, --parents
Remove directories and any intervening parent directories that become empty as a result; useful for
removing subdirectory trees.

--verbose
Turn on verbose mode; print message for each directory as it is processed.
--version
Print version information and then exit.

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rmmod rmmod [option] modules
System administration command. Unload a module or list of modules from the kernel. This command is
successful only if the specified modules are not in use and no other modules are dependent on them.

Option
-r
Recursively remove stacked modules (all modules that use the specified module).

rootflags rootflags [option] image [flags [offset]]
System administration command. Sets flags for a kernel image. If no arguments are specified, print flags for the
kernel image. flags is a 2-byte integer located at offset 498 in a kernel image. Currently the only effect of flags is
to mount the root filesystem in read-only mode if flags is non-zero. You may change flags by specifying the
kernel image to change, the new flags, and the byte-offset at which to place the new information (the default is
498). Note that rdev -R is a synonym for rootflags. If LILO is used, rootflags is not needed. flags can be set
from the LILO prompt during a boot.

Option
-o offset
Same as specifying an offset as an argument.

route route [option] [command]
TCP/ IP command. Manually manipulate the routing tables normally maintained by routed. route accepts two
commands: add, to add a route, and del, to delete a route. The two commands have the following syntax:

add [-net | -host] address [gw gateway][netmask mask] [mss tcp-mss] [dev device]del address

address is treated as a plain route unless -net is specified or address is found in /etc/ networks. -host can be used
to specify that address is a plain route whether or not it is found in /etc/ networks. The keyword default means to
use this route for all requests if no other route is known. You can specify the gateway through which to route
packets headed for that address, its netmask, TCP mss, and the device with which to associate the route. Only a
privileged user may modify the routing tables.

If no command is specified, route prints the routing tables.
Option
-n
Show numerical addresses; do not look up hostnames. (Useful if DNS is not functioning properly.)

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routed routed [options] [logfile]
TCP/ IP command. Network routing daemon. routed is invoked by a privileged user at boot time to manage the
Internet routing tables. The routing daemon uses a variant of the Xerox NS Routing Information Protocol in
maintaining up-to-date kernel routing-table entries. When routed is started, it uses the SIOCGIFCONF ioctl call
to find those directly connected interfaces configured into the system and marked up. routed transmits a
REQUEST packet on each interface, then enters a loop, listening for REQUEST and RESPONSE packets from
other hosts. When a REQUEST packet is received, routed formulates a reply based on the information
maintained in its internal tables. The generated RESPONSE packet contains a list of known routes. Any
RESPONSE packets received are used to update the routing tables as appropriate.

When an update is applied, routed records the change in its internal tables, updates the kernel routing table, and
generates a RESPONSE packet reflecting these changes to all directly connected hosts and networks.

Options
-d
Debugging mode. Log additional information to the logfile.
-g

Offer a route to the default destination.
-q

Opposite of -s option.
-s

Force routed to supply routing information, whether it is acting as an internetwork router or not.
-t

Stop routed from going into background and releasing itself from the controlling terminal, so that
interrupts from the keyboard will kill the process.

rpcgen rpcgen [options] file
Parse file, which should be written in the RPC language, and produce a program written in C that implements the
RPC code. Place header code generated from file. x in file. h, XDR routines in file_ xdr. c, server code in file_ svc. c,
and client code in file_ clnt. c. Lines preceded by % are not parsed. By default, rpcgen produces SunOS 4.1-
compatible code.

-a
Produce all files (client and server).
-5
Produce SVR4-compatible code.
-c
Create XDR routines. Cannot be used with other options.
-C
Produce ANSI C code (default).
-Dname[= value]
Define the symbol name, and set it equal to value or 1.

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-h

Produce a header file. With -T, make the file support RPC dispatch tables. Cannot be used with other
options.

-I
Produce an inetd-compatible server.
-K secs
Specify amount of time that the server should wait after replying to a request and before exiting. Default
is 120. A secs of -1 prevents the program from ever exiting.

-l
Produce client code. Cannot be used with other options.
-m
Produce server code only, suppressing creation of a "main" routine. Cannot be used with other options.
-N
New style. Allow multiple arguments for procedures. Not necessarily backward compatible.
-o [file]
Print output to file or standard output.
-Ss
Create skeleton server code only.
-t
Create RPC dispatch table. Cannot be used with other options.
-T
Include support for RPC dispatch tables.

rpcinfo rpcinfo [options] [host] [program] [version]
NFS/ NIS command. Report RPC information. program can be either a name or a number. If a version is
specified, rpcinfo attempts to call that version of the specified program. Otherwise, it attempts to find all the
registered version numbers for the specified program by calling Version 0, and it attempts to call each registered
version.

Options
-b program version
Make an RPC broadcast to the specified program and version, using UDP, and report all hosts that
respond.

-d program version
Delete the specified version of program's registration. Can be executed only by the user who added the
registration or a privileged user.

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-n portnum
Use portnum as the port number for the -t and -u options, instead of the port number given by the
portmapper.

-p [host]
Probe the portmapper on host and print a list of all registered RPC programs. If host is not specified, it
defaults to the value returned by hostname.

-t host program [version]
Make an RPC call to program on the specified host, using TCP, and report whether a response was
received.

-u host program [version]
Make an RPC call to program on the specified host, using UDP, and report whether a response was
received.

Examples
To show all of the RPC services registered on the local machine, use:
$ rpcinfo -pTo show all of the RPC services registered on the machine named klaxon, use:
$ rpcinfo -p klaxonTo show all machines on the local net that are running the Network Information Service (NIS), use:
$ rpcinfo -b ypserv version | uniqwhere version is the current NIS version obtained from the results of the -p switch earlier in this list.

rpm rpm [options]
The Red Hat Package Manager. A freely available packaging system for software distribution and installation.
RPM packages are built, installed, and queried with the rpm command. For detailed information on rpm, see
Chapter 5, "Red Hat and Debian Package Managers".

rsh rsh [options] host [command]
Execute command on remote host, or, if no command is specified, begin an interactive shell on the remote host
using rlogin.

Options
-d
Enable socket debugging.
-k
Cause rsh to obtain tickets for the remote host in realm instead of the remote host's realm as determined
by krb_ realmofhost( 3).

-l username

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Attempt to log in as username. By default, the name of the user executing rsh is used.
-n
Redirects the input to rsh from the special device /dev/ null. (This should be done when backgrounding
rsh from a shell prompt, to direct the input away from the terminal.)

-x
Turns on DES encryption for all data exchange.
-K
Suppress Kerberos authentication.

rshd rshd [options]
TCP/ IP command. Remote shell server for programs such as rcmd and rcp, which need to execute a
noninteractive shell on remote machines. rshd is started by inetd and must have an entry in inetd's configuration
file, /etc/ inetd. conf.

All options are exactly the same as those in rlogind, except for -L, which is unique to rshd.
Option
-L
Log all successful connections and failed attempts via syslogd.

rstat rstat host
TCP/ IP command. Summarize host's system status: the current time, uptime, and load averages --the average
number of jobs in the run queue. Queries the remote host's rstat_ svc daemon.

run-parts run-parts [options] [directory]
System administration command. Run, in lexical order, all scripts found in directory. Exclude scripts whose
filenames include nonalphanumeric characters (besides underscores and hyphens).

Options
--
Interpret all subsequent arguments as filenames, not options.
--test
Print information listing which scripts would be run, but suppress actual execution of them.
--umask= umask
Specify umask. The default is 022.

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runlevel runlevel
System administration command. Display the previous and current system runlevels.

ruptime ruptime [options]
TCP/ IP command. Provide information on how long each machine on the local network has been up and which
users are logged in to each. If a machine has not reported in for 11 minutes, assume it is down. The listing is
sorted by hostname.

Options
-a
Include users who have been idle for more than one hour.
-l
Sort machines by load average.
-r
Reverse the normal sort order.
-t
Sort machines by uptime.
-u
Sort machines by the number of users logged in.

rusers rusers [options] [host]
TCP/ IP command. List the users logged on to host, or to all local machines, in who format (hostname,
usernames).

Options
-a
Include machines with no users logged in.
-l
Include more information: tty, date, time, idle time, remote host.

rwall rwall host [file]
TCP/ IP command. Print a message to all users logged on to host. If file is specified, read the message from it;
otherwise, read from standard input.

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rwho rwho [option]
Report who is logged on for all machines on the local network (similar to who).
Option
-a
List users even if they've been idle for more than one hour.

rwhod rwhod
TCP/ IP command. System status server that maintains the database used by the rwho and ruptime programs. Its
operation is predicated on the ability to broadcast messages on a network. As a producer of information, rwhod
periodically queries the state of the system and constructs status messages, which are broadcast on a network. As
a consumer of information, it listens for other rwhod servers' status messages, validates them, then records them
in a collection of files located in the directory /var/ spool/ rwho. Messages received by the rwhod server are
discarded unless they originated at an rwhod server's port. Status messages are generated approximately once
every 3 minutes.

script script [option] [file]
Fork the current shell and make a typescript of a terminal session. The typescript is written to file. If no file is
given, the typescript is saved in the file typescript. The script ends when the forked shell exits, usually with Ctrl-D
or exit.

Option
-a
Append to file or typescript instead of overwriting the previous contents.

sed sed [options] [command] [files]
Stream editor --edit one or more files without user interaction. See Chapter 12, "The sed Editor", for more
information.

sendmail sendmail [flags] [address...]
System administration command. sendmail is a mail transfer agent (MTA) or, more simply, a mail router. It
accepts mail from a user's mail program, interprets the mail address, rewrites the address into the proper form for
the delivery program, and routes the mail to the correct delivery program.

Command-line flags
-bx
Set operation mode to x. Operation modes are:
a
Run in ARPAnet mode.
d

Run as a daemon.
i

Initialize the alias database.
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m

Deliver mail (default).
p

Print the mail queue.
s

Speak SMTP on input side.
t

Run in test mode.
v

Verify addresses; do not collect or deliver.
-C file

Use configuration file file.
-d level

Set debugging level.
-F name

Set full name of user to name.
-f name

Sender's name is name.
-h cnt

Set hop count (number of times message has been processed by sendmail) to cnt.
-n

Do not alias or forward.
-o x value

Set option x to value value. Options are described below.
-p protocol

Receive messages via the protocol protocol.
-q [time]

Process queued messages immediately, or at intervals indicated by time (for example, -q30m for every
half hour).
-r name

Obsolete form of -f.
-t

Read head for To:, Cc:, and Bcc: lines, and send to everyone on those lists.
-v

Verbose.
-X file

Log all traffic to file. Not to be used for normal logging.
Configuration options
The following options can be set with the -o flag on the command line or the O line in the configuration file:
7

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Format all incoming messages in 7 bits.
amin

If the D option is set, wait min minutes for the aliases file to be rebuilt before returning an alias database
out-of-date warning.
Afile

Use alternate alias file.
bminblocks[/ maxsize]

Require at least minblocks to be free, and optionally set the maximum message size to maxsize. If maxsize
is omitted, the slash is optional.
Bchar

Set unquoted space replacement character.
c

On mailers that are considered "expensive" to connect to, don't initiate immediate connection.
Cnum

Checkpoint the queue when mailing to multiple recipients. sendmail will rewrite the list of recipients
after each group of num recipients has been processed.
dx

Set the delivery mode to x. Delivery modes are d for deferred delivery, i for interactive (synchronous)
delivery, b for background (asynchronous) delivery, and q for queue only --i. e., deliver the next time the
queue is run.
D

Try to automatically rebuild the alias database if necessary.
ex

Set error processing to mode x. Valid modes are m to mail back the error message, w to write back the
error message, p to print the errors on the terminal (default), q to throw away error messages, and e to do
special processing for the BerkNet.
Etext

Set error message header. text is either text to add to an error message or the name of a file. A filename
must include its full path and begin with a /.
f

Save Unix-style From lines at the front of messages.
Fmode

Set default file permissions for temporary files. If this option is missing, default permissions are 0644.
G

Compare local mail names to the GECOS section in the password file.
g n

Default group ID to use when calling mailers.
Hfile

SMTP help file.
h num

Allow a maximum of num hops per message.
i

Do not take dots on a line by themselves as a message terminator.
I arg

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Use DNS lookups and tune them. Queue messages on connection refused. The arg arguments are
identical to resolver flags without the RES_ prefix. Each flag can be preceded by a plus or minus to
enable or disable the corresponding name server option. There must be a whitespace between the I and
the first flag.
j

Use MIME format for error messages.
Jpath

Set an alternative .forward search path.
knum

Specify size of the connection cache.
Ktime

Time out connections after time.
l

Do not ignore Errors-To header.
Ln

Specify log level.
m

Send to me (the sender) also if I am in an alias expansion.
MXvalue

Define a macro's value in command line. Assign value to macro X.
n

When running newaliases, validate the right side of aliases.
o

If set, this message may have old-style headers. If not set, this message is guaranteed to have new-style
headers (i. e., commas instead of spaces between addresses).
pwhat, what,...

Tune how private you want the SMTP daemon. The what arguments should be separated from one
another by commas. The what arguments may be any of the following:

public
Make SMTP fully public (default).
needmailhelo

Require site to send HELO or ELHO before sending mail.
needexpnhelo

Require site to send HELO or ELHO before answering an address expansion request.
needvrfyhelo

Like preceding argument but for verification requests.
noexpn

Deny all expansion requests.
novrfy

Deny all verification requests.
authwarnings

Insert special headers in mail messages advising recipients that the message may not be authentic.
goaway

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Set all of the previous arguments (except public).
restrictmailq

Allow only users of the same group as the owner of the queue directory to examine the mail
queue.
restrictqrun

Limit queue processing to root and the owner of the queue directory.
Puser

Send copies of all failed mail to user (usually postmaster).
qfact

Multiplier (factor) for high-load queuing.
Qqueuedir

Select the directory in which to queue messages.
R

Don't prune route addresses.
Sfile

Save statistics in the named file.
s

Always instantiate the queue file, even under circumstances in which it is not strictly necessary.
Ttime

Set the timeout on undelivered messages in the queue to the specified time.
tstz, dtz

Set name of the time zone.
Udatabase

Consult the user database database for forwarding information.
uN

Set default user ID for mailers.
v

Run in verbose mode.
Vhost

Fall-back MX host. host should be the fully qualified domain name of the fallback host.
w

Use a record for an ambiguous MX.
xload

Queues messages when load level is higher than load.
Xload

Refuse SMTP connections when load is higher than load.
yfactor

Penalize large recipient lists by factor.
Y

Deliver each job that is run from the queue in a separate process. This helps limit the size of running
processes on systems with very low amounts of memory.
zfactor

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Multiplier for priority increments. This determines how much weight to give to a message's precedence
header. sendmail's default is 1800.
Zinc

Increment priority of items remaining in queue by inc after each job is processed. sendmail uses 90,000
by default.

sendmail support files
/usr/ lib/ sendmail
Binary of sendmail.
/usr/ bin/ newaliases

Link to /usr/ lib/ sendmail; causes the alias database to be rebuilt.
/usr/ bin/ mailq

Prints a listing of the mail queue.
/etc/ sendmail. cf

Configuration file, in text form.
/etc/ sendmail. hf

SMTP help file.
/usr/ lib/ sendmail. st

Statistics file. Doesn't need to be present.
/etc/ aliases

Alias file, in text form.
/etc/ aliases.{ pag, dir}

Alias file in dbm format.
/var/ spool/ mqueue

Directory in which the mail queue and temporary files reside.
/var/ spool/ mqueue/ qf

Control (queue) files for messages.
/var/ spool/ mqueue/ df

Data files.
/var/ spool/ mqueue/ lf

Lockfiles.
/var/ spool/ mqueue/ tf

Temporary versions of af files, used during queue-file rebuild.
/var/ spool/ mqueue/ nf

Used when creating a unique ID.
/var/ spool/ mqueue/ xf

Transcript of current session.

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setfdprm setfdprm [options] device [name]
Load disk parameters used when autoconfiguring floppy devices.
Options
-c device
Clear parameters of device.
-n device
Disable format-detection messages for device.
-p device [name | parameter]
Permanently reset parameters for device. You can use name to specify a configuration, or you can specify
individual parameters. The parameters that can be specified are dev, size, sect, heads, tracks, stretch,
gap, rate, spec1, or fmt_ gap. Consult /etc/ fdprm for the original values.

-y device
Enable format-detection messages for device.

setsid setsid command [arguments]
System administration command. Execute the named command and optional command arguments in a new
session.

sh sh [options] [file [arguments]]
The standard Unix shell, a command interpreter into which all other commands are entered. On Linux, this is
just another name for the bash shell. For more information, see Chapter 7, "bash: The Bourne-Again Shell", .

shar shar [options] files
shar -S [options]
Create shell archives (or shar files) that are in text format and can be mailed. These files may be unpacked later
by executing them with /bin/ sh. Other commands may be required on the recipient's system, such as compress,
gzip, and uudecode. The resulting archive is sent to standard output, unless the -o option is given.

Options
-a, --net-headers
Allows automatic generation of headers. The -n option is required if the -a option is used.
-b bits, --bits-per-code= bits
Use -b bits as a parameter to compress (when doing compression). Default value is 12. The -b option
automatically turns on -Z.

-c, --cut-mark
Start the shar file with a line that says "Cut here."
-d delimiter, --here-delimiter= delimiter

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Use delimiter for the files in the shar instead of SHAR_ EOF.
-f, --basename
Causes only simple filenames to be used when restoring, which is useful when building a shar from
several directories or another directory. (If a directory name is passed to shar, the substructure of that
directory will be restored whether or not -f is used.)

-g level, --level-for-gzip= level
Use -level as a parameter to gzip (when doing compression). Default is 9. The -g option turns on the -z
option by default.

--help
Print a help summary on standard output, then exit.
-l nn, --whole-size-limit= nn
Limit the output file size to nn kilobytes but don't split input files. Requires use of -o.
-m, --no-timestamp
Don't generate touch commands to restore the file modification dates when unpacking files from the
archive.

-n name, --archive-name= name
Name of archive to be included in the header of the shar files. Required if the -a option is used.
--no-i18n
Do not produce internationalized shell archives; use default English messages. By default, shar produces
archives that will try to output messages in the unpacker's preferred language (as determined by
LANG/ LC_ MESSAGES).

-o prefix, --output-prefix= prefix
Save the archive to files prefix. 01 through prefix. nn (instead of sending it to standard output). This option
must be used when either -l or -L is used.

-p, --intermix-type
Allow positional parameter options. The options -B, -T, -z, and -Z may be embedded, and files to the
right of the option will be processed in the specified mode.

--print-text-domain-dir
Print the directory shar looks in to find messages files for different languages, then immediately exit.
-q, --quiet, --silent
Turn off verbose mode.
-s who@ where, --submitter= who@ where
Supply submitter name and address, instead of allowing shar to determine it automatically.
--version

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Print the version number of the program on standard output, then exit.

-w, --no-character-count
Do not check each file with wc -c after unpacking. The default is to check.
-x, --no-check-existing
Overwrite existing files without checking. Default is to check and not overwrite existing files. If -c is
passed as a parameter to the script when unpacking (sh archive -c), existing files will be overwritten
unconditionally. See also -X.

-z, --gzip
gzip and uuencode all files prior to packing. Must be unpacked with uudecode and gunzip (or zcat).
-B, --uuencode
Treat all files as binary; use uuencode prior to packing. This increases the size of the archive, and it must
be unpacked with uudecode.

-D, --no-md5-digest
Do not use md5sum digest to verify the unpacked files. The default is to check.
-F, --force-prefix
Force the prefix character to be prepended to every line even if not required. May slightly increase the
size of the archive, especially if -B or -Z is used.

-L nn, --split-size-limit= nn
Limit output file size to nn kilobytes and split files if necessary. The archive parts created with this option
must be unpacked in correct order. Requires use of -o.

-M, --mixed-uuencode
Pack files in mixed mode (the default). Distinguishes files as either text or binary; binaries are uuencoded
prior to packing.

-P, --no-piping
Use temporary files instead of pipes in the shar file.
-Q, --quiet-unshar
Disable verbose mode.
-S, --stdin-file-list
Read list of files to be packed from standard input rather than from the command line. Input must be in a
form similar to that generated by the find command, with one filename per line.

-T, --text-files
Treat all files as text.
-V, --vanilla-operation
Produce shars that rely only upon the existence of sed and echo in the unsharing environment.

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-X, --query-user

Prompt user to ask if files should be overwritten when unpacking.
-Z, --compress
Compress and uuencode all files prior to packing.

showmount showmount [options] [host]
NFS/ NIS command. Show information about an NFS server. This information is maintained by the mountd
server on host. The default value for host is the value returned by hostname. With no options, show the clients
that have mounted directories from the host. showmount is usually found in /usr/ sbin, which is not in the default
search path.

Options
-a, --all
Print all remote mounts in the format:
hostname: directorywhere hostname is the name of the client and directory is the root of the filesystem that has been mounted.
-d, --directories
List directories that have been remotely mounted by clients.
-e, --exports
Print the list of exported filesystems.
-h, --help
Provide a short help summary.
--no-headers
Do not print headers.
-v, --version
Report the current version number of the program.

shutdown shutdown [options] when [message]
System administration command. Terminate all processing. when may be a specific time (in hh: mm format), a
number of minutes to wait (in +m format), or now. A broadcast message notifies all users to log off the system.
Processes are signaled with SIGTERM, to allow them to exit gracefully. /etc/ init is called to perform the actual
shutdown, which consists of placing the system in runlevel 1. Only privileged users can execute the shutdown
command. Broadcast messages, default or defined, are displayed at regular intervals during the grace period; the
closer the shutdown time, the more frequent the message.

Options
-c
Cancel a shutdown that is in progress.

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-f

Reboot fast, by suppressing the normal call to fsck when rebooting.
-h
Halt the system when shutdown is complete.
-k
Print the warning message, but suppress actual shutdown.
-n
Perform shutdown without a call to init.
-r
Reboot the system when shutdown is complete.
-t sec
Ensure a sec-second delay between killing processes and changing the runlevel.

size size [options] [objfile...]
Print the number of bytes of each section of objfile and its total size. If objfile is not specified, a. out is used.
Options
-d
Display the size in decimal and hexadecimal.
--format format
Imitate the size command from either System V (--format sysv) or BSD (--format berkeley).
-o
Display the size in octal and hexadecimal.
--radix num
Specify how to display the size: in hexadecimal and decimal (if num is 10 or 16) or hexadecimal and
octal (if num is 8).

-x
Display the size in hexadecimal and decimal.
-A
Imitate System V's size command.
-B
Imitate BSD's size command.

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slattach slattach [options] [tty]
TCP/ IP command. Attach serial lines as network interfaces, thereby preparing them for use as point-to-point
connections. Only a privileged user may attach or detach a network interface.

Options
-c command
Run command when the connection is severed.
-d
Debugging mode.
-e
Exit immediately after initializing the line.
-h
Exit when the connection is severed.
-l
Create UUCP-style lockfile in /var/ spool/ uucp.
-L
Enable 3-wire operation.
-m
Suppress initialization of the line to 8 bits raw mode.
-n
Similar to mesg -n.
-p protocol
Specify protocol, which may be slip, adaptive, ppp, or kiss.
-q
Quiet mode; suppress messages.
-s speed
Specify line speed.

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sleep sleep amount[ units]
Wait a specified amount of time before executing another command. The default for units is seconds.

Time Units
s seconds
m minutes
h hours
d days

sort sort [options] [files]
Sort the lines of the named files. Compare specified fields for each pair of lines, or, if no fields are specified,
compare them by byte, in machine collating sequence. See also uniq, comm, and join.

Options
-b
Ignore leading spaces and tabs.
-c
Check whether files are already sorted, and, if so, produce no output.
-d
Sort in dictionary order.
-f
Fold --ignore uppercase/ lowercase differences.
--help
Print a help message and then exit.
-i
Ignore nonprinting characters (those outside ASCII range 040-176).
-m
Merge (i. e., sort as a group) input files.
-n
Sort in arithmetic order.
-ofile
Put output in file.
-r
Reverse the order of the sort.
-tc

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Separate fields with c (default is a tab).

-u
Identical lines in input file appear only one (unique) time in output.
-zrecsz
Provide recsz bytes for any one line in the file. This option prevents abnormal termination of sort in
certain cases.

+n [-m]
Skip n fields before sorting, and sort up to field position m. If m is missing, sort to end of line. Positions
take the form a. b, which means character b of field a. If .b is missing, sort at the first character of the
field.

-k n[, m]
Similar to +. Skip n-1 fields and stop at m-1 fields (i. e., start sorting at the nth field, where the fields are
numbered beginning with 1).

--version
Print version information and then exit.
-M
Attempt to treat the first three characters as a month designation (JAN, FEB, etc.). In comparisons, treat
JAN < FEB and any valid month as less than an invalid name for a month.

-T tempdir
Directory pathname to be used for temporary files.
Examples
List files by decreasing number of lines:
wc -l * | sort -rAlphabetize a list of words, remove duplicates, and print the frequency of each word:
sort -fd wordlist | uniq -cSort the password file numerically by the third field (user ID):
sort +2n -t: /etc/ passwd

split split [option] [infile] [outfile]
Split infile into equal-sized segments. infile remains unchanged, and the results are written to outfileaa,
outfileab, and so on. (default is xaa, xab, etc.). If infile is -(or missing), standard input is read. See also csplit.

Options
-n, -l n, --lines= n
Split infile into n-line segments (default is 1000).

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-b n[ bkm], --bytes= n[ bkm]

Split infile into n-byte segments. Alternate blocksizes may be specified:
b
512 bytes
k
1 kilobyte
m
1 megabyte
-C bytes[ bkm], --line-bytes= bytes[ bkm]
Put a maximum of bytes into file; insist on adding complete lines.
--help
Print a help message and then exit.
--verbose
Print a message for each output file.
--version
Print version information and then exit.
-Take
input from the standard input.
Examples
Break bigfile into 1000-line segments:
split bigfileJoin four files, then split them into 10-line files named new. aa, new. ab, and so on. Note that without the -, new.
would be treated as a nonexistent input file:

cat list[ 1-4] | split -10 -new.

stat stat filename [filenames . . . ]
Print out the contents of an inode as they appear to the stat system call in a human-readable format. The error
messages "Can't stat file" or "Can't lstat file" usually mean the file doesn't exist. "Can't readlink file" generally
indicates that something is wrong with a symbolic link.

Output
Sample output from the command:
stat /File: "/"

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Size: 1024 Filetype: Directory Mode: (0755/ drwxr-xr-x) Uid: ( 0/ root) Gid: ( 0/ system) Device: 3,3 Inode: 2 Links: 21 Access: Tue Apr 11 04: 02: 01 2000( 00000.11: 47: 35) Modify: Wed Nov 17 11: 46: 38 1999( 00146.03: 02: 58) Change: Wed Nov 17 11: 46: 38 1999( 00146.03: 02: 58)

strace strace [options] command [arguments]
Trace the system calls and signals for command and arguments. strace shows you how data is passed between
the program and the system kernel. With no options, strace prints a line to stderr for each system call. It shows
the call name, arguments given, the return value, and any error messages generated. A signal is printed with both
its signal symbol and a descriptive string.

Options
-a n
Align the return values in column n.
-c
Count all calls and signals and create a summary report when the program has ended.
-d
Debug mode. Print debugging information for strace on stderr.
-e keyword[=[!] values
Pass an expression to strace to limit the types of calls or signals that are traced or change how they are
displayed. The values for these expressions can be given as a comma-separated list. Preceding the list
with an exclamation mark (!) negates the list. The special values of all and none are valid, as are the
values listed with the following keywords.

abbrev= names
Abbreviate output from large structures for system calls listed in names.
read= descriptors
Print all data read from the given file descriptors.
signal= symbols
Trace the listed signal symbols (for example, signal= SIGIO, SIGHUP).
trace= values
Trace the listed values. values may be a list of system call names or one of the following sets of
system calls:

file Calls that take a filename as an argument
ipc Interprocess communication
network Network-related
process Process management
signal Signal-related
verbose= names

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Unabbreviate structures for the given system call names. Default is none.

write= descriptors
Print all data written to the given file descriptors.
-f
Trace forked processes.
-ff
Write system calls for forked processes to separate files named filename. pid when using the -o option.
-h
Print help and exit.
-i
Print instruction pointer with each system call.
-o filename
Write output to filename instead of stderr. If filename starts with the pipe symbol |, treat the rest of the
name as a command to which output should be piped.

-O n
Override strace's built-in timing estimates, and just subtract n microseconds from the timing of each
system call to adjust for the time it takes to measure thestentry> call.

-p pid
Attach to the given process ID and begin tracking. strace can track more than one process if more than
one option -p is given. Type Ctrl-c to end the trace.

-q
Quiet mode. Suppress attach and detach messages from strace.
-r
Relative timestamp. Print time in microseconds between system calls.
-s n
Print only the first n characters of a string. Default value is 32.
-S value
Sort output of -c option by the given value. value may be calls, name, time, or nothing. By default it is
sorted by time.

-T
Print time spent in each system call.
-t
Print time of day on each line of output.

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-tt
Print time of day with microseconds on each line of output.
-ttt
Print timestamp on each line as number of seconds since the Epoch.
-u username
Run command as username. Needed when tracing setuid and setgid programs.
-V
Print version and exit.
-v
Verbose. Do not abbreviate structure information.
-x
Print all non-ASCII strings in hexadecimal.
-xx
Print all strings in hexadecimal.

strfile strfile [options] input_ file [output_ file]
unstr [-c delimiter] input_ file[. ext] [output_ file]
strfile creates a random-access file for storing strings. The input file should be a file containing groups of lines
separated by a line containing a single percent sign (or other specified delimiter character). strfile creates an
output file that contains a header structure and a table of file offsets for each group of lines, allowing random
access of the strings. The output file, if not specified on the command line, is named sourcefile. dat. unstr undoes
the work of strfile, printing out the strings contained in the input file in the order that they are listed in the
header file data. If no output file is specified, unstr prints to standard output; otherwise, it prints to the file
specified. unstr can also globally change the delimiter character in a strings file.

Options
Of the following options, only -c can be used with unstr. All other options apply to strfile alone.
-c delimiter
Change the delimiting character from the percent sign to delimiter. Valid for both strfile and unstr.
-i
Ignore case when ordering the strings.
-o
Order the strings alphabetically.
-r
Randomize access to the strings.

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-s
Run silently; don't give a summary message when finished.
-x
Set the STR_ ROTATED bit in the header str_ flags field.

strings strings [options] files
Search each file specified and print any printable character strings found that are at least four characters long and
followed by an unprintable character.

Options
-, -a, --all
Scan entire object files; default is to scan only the initialized and loaded sections for object files.
-f, --print-file-name
Print the name of the file before each string.
-min-len, -n min-len, --bytes= min-len
Print only strings that are at least min-len characters.
-t base, --radix= base
Print the offset within the file before each string, in the format specified by base:
d
Decimal
o
Octal
x
Hexadecimal
--target= format
Specify an alternative object code format to the system default.
-o
Same as -t o.
--help
Print help message and then exit.
-v, --version
Print version information and then exit.

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strip strip [options] files
Remove symbols from object files, thereby reducing file sizes and freeing disk space.
Options
-F format, --target= format
Expect the input file to be in the format format.
-O format, --output-target= format
Write output file in format.
-R section, --remove-section= section
Delete section.
-s, --strip-all
Strip all symbols.
-S, -g,--strip-debug
Strip debugging symbols.
-x, --discard-all
Strip nonglobal symbols.
-X, --discard-locals
Strip local symbols that were generated by the compiler.
-v, --verbose
Verbose mode.

stty stty [options] [modes]
Set terminal I/ O options for the current standard input device. Without options, stty reports the terminal settings
that differ from those set by running stty sane, where a ^ indicates the Ctrl key and ^` indicates a null value.
Most modes can be negated using an optional -(shown in brackets). The corresponding description is also
shown in brackets. Some arguments use non-POSIX extensions; these are marked with a *.

Options
-a, --all
Report all option settings.
-g
Report settings in hex.
Control modes
n
Set terminal baud rate to n (e. g., 2400).
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[-] clocal
[Enable] disable modem control.
[-] cread
[Disable] enable the receiver.
csbits
Set character size to bits, which must be 5, 6, 7, or 8.
[-] cstopb
[1] 2 stop bits per character.
[-] hup
[Do not] hang up connection on last close.
[-] hupcl
Same as previous.
ispeed n
Set terminal input baud rate to n.
ospeed n
Set terminal output baud rate to n.
[-] parenb
[Disable] enable parity generation and detection.
[-] parodd
Use [even] odd parity.
[-] crtscts*
[Disable] enable RTS/ CTS handshaking.
Flow control modes
The following flow control modes are available by combining the ortsfl, ctsflow, and rtsflow flags:

Flag Settings Flow Control Mode
ortsfl rtsflow ctsflow Enable unidirectional flow control.
ortsfl rtsflow -ctsflow Assert RTS when ready to send.
ortsfl -rtsflow ctsflow No effect.
ortsfl -rtsflow -ctsflow Enable bidirectional flow control.
-ortsfl rtsflow ctsflow Enable bidirectional flow control.
-ortsfl rtsflow -ctsflow No effect.
-ortsfl -rtsflow ctsflow Stop transmission when CTS drops.
-ortsfl -rtsflow -ctsflow Disable hardware flow control.

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Input modes
[-] brkint
[Do not] signal INTR on break.
[-] icrnl
[Do not] map CR to NL on input.
[-] ignbrk
[Do not] ignore break on input.
[-] igncr
[Do not] ignore CR on input.
[-] ignpar
[Do not] ignore parity errors.
[-] inlcr
[Do not] map NL to CR on input.
[-] inpck
[Disable] enable input parity checking.
[-] istrip
[Do not] strip input characters to 7 bits.
[-] iuclc*
[Do not] map uppercase to lowercase on input.
[-] ixany*
Allow [XON] any character to restart output.
[-] ixoff [-] tandem
[Do not] send START/ STOP characters when queue is nearly empty/ full.
[-] ixon
[Disable] enable START/ STOP output control.
[-] parmrk
[Do not] mark parity errors.
[-] imaxbel*
When input buffer is too full to accept a new character, [flush the input buffer] beep without flushing the
input buffer.

Output modes
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bsn
Select style of delay for backspaces (0 or 1).
crn
Select style of delay for carriage returns (0-3).
ffn
Select style of delay for formfeeds (0 or 1).
nln
Select style of delay for linefeeds (0 or 1).
tabn
Select style of delay for horizontal tabs (0-3).
vtn
Select style of delay for vertical tabs (0 or 1).
[-] ocrnl*
[Do not] map CR to NL on output.
[-] ofdel*
Set fill character to [NULL] DEL.
[-] ofill*
Delay output with [timing] fill characters.
[-] olcuc*
[Do not] map lowercase to uppercase on output.
[-] onlcr*
[Do not] map NL to CR-NL on output.
[-] onlret*
On the terminal, NL performs [does not perform] the CR function.
[-] onocr*
Do not [do] output CRs at column 0.
[-] opost
[Do not] postprocess output.
Local modes
[-] echo

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[Do not] echo every character typed.
[-] echoe, [-] crterase
[Do not] echo ERASE character as BS-space-BS string.
[-] echok
[Do not] echo NL after KILL character.
[-] echonl
[Do not] echo NL.
[-] icanon
[Disable] enable canonical input (ERASE, KILL, WERASE, and RPRINT processing).
[-] iexten
[Disable] enable extended functions for input data.
[-] isig
[Disable] enable checking of characters against INTR, SUSPEND, and QUIT.
[-] noflsh
[Enable] disable flush after INTR or QUIT.
[-] tostop*
[Do not] send SIGTTOU when background processes write to the terminal.
[-] xcase*
[Do not] change case on local output.
[-] echoprt, [-] prterase*
When erasing characters, echo them backward, enclosed in \ and /.
[-] echoctl. [-] ctlecho*
Do not echo control characters literally. Use hat notation (e. g., ^Z).
[-] echoke [-] crtkill*
Erase characters as specified by the echoprt and echoe settings (default is echoctl and echok settings).
Control assignments
ctrl-char c
Set control character to c. ctrl-char is dsusp (flush input and then send stop), eof, eol, eol2 (alternate end-of-
line), erase, intr, lnext (treat next character literally), kill, rprnt (redraw line), quit, start, stop, susp,
swtch, or werase (erase previous word). c can be a literal control character, a character in hat notation
(e. g., ^Z), in hex (must begin with 0x), in octal (must begin with 0), or in decimal. Disable the control
character with values of ^-or undef.

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min n

Set the minimum number of characters that will satisfy a read until the time value has expired when -icanon
is set.

time n
Set the number of tenths of a second before reads time out if the min number of characters have not been
read when -icanon is set.

line i
Set line discipline to i (1-126).
Combination modes
cooked
Same as -raw.
[-] evenp [-] parity
Same as [-] parenb and cs[ 8] 7.
[-] parity
Same as [-] parenb and cs[ 8] 7.
ek
Reset ERASE and KILL characters to Ctrl-h and Ctrl-u, their defaults.
[-] lcase
[Un] set xcase, iuclc, and olcuc.
[-] LCASE
Same as [-] lcase.
[-] nl
[Un] set icrnl and onlcr. -nl also unsets inlcr, igncr, ocrnl, and onlret, icrnl, onlcr.
[-] oddp
Same as [-] parenb, [-] parodd, and cs7[ 8].
[-] raw
[Disable] enable raw input and output (no ERASE, KILL, INTR, QUIT, EOT, SWITCH, or output
postprocessing).

sane
Reset all modes to reasonable values.
[-] tabs*
[Expand to spaces] preserve output tabs.

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[-] cbreak

Same as -icanon.
[-] pass8
Same as -parenb -istrip cs8.
[-] litout
Same as -parenb -istrip cs8.
[-] decctlq*
Same as -ixany.
crt
Same as echoe echoctl echoke.
dec
Same as echoe echoctl echoke -ixany. Additionally, set INTERRUPT to ^C, ERASE to DEL, and KILL
to ^U.

Special settings
ispeed speed
Specify input speed.
ospeed speed
Specify output speed.
rows rows*
Specify number of rows.
cols columns, columns columns*
Specify number of columns.
size*
Display current row and column settings.
line discipline*
Specify line discipline.
speed
Display terminal speed.

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su su [option] [user] [shell_ args]
Create a shell with the effective user-ID user. If no user is specified, create a shell for a privileged user (that is,
become a superuser). Enter EOF to terminate. You can run the shell with particular options by passing them as
shell_ args (e. g., if the shell runs sh, you can specify -c command to execute command via sh or -r to create a
restricted shell).

Options
-, -l, --login
Go through the entire login sequence (i. e., change to user's environment).
-c command, --command= command
Execute command in the new shell and then exit immediately. If command is more than one word, it
should be enclosed in quotes --for example:

su -c 'find / -name \*. c -print' nobody-f, --fast
Start shell with -f option. In csh and tcsh, this suppresses the reading of the .cshrc file. In bash, this
suppresses filename pattern expansion.

-m, -p, --preserve-environment
Do not reset environment variables.
-s shell, --shell= shell
Execute shell, not the shell specified in /etc/ passwd, unless shell is restricted.
--help
Print a help message and then exit.
--version
Print version information and then exit.

sum sum [options] files
Calculate and print a checksum and the number of (1KB) blocks for file. Useful for verifying data transmission.
Options
-r
The default setting. Use the BSD checksum algorithm.
-s, --sysv
Use alternate checksum algorithm as used on System V. The blocksize is 512 bytes.
--help
Print a help message and then exit.
--version
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Print the version number and then exit.
swapdev swapdev [option] [image [swapdevice [offset]]]
System administration command. If no arguments are given, display usage information about the swap device. If
just the location of the kernel image is specified, print the information found there. To change that information,
specify the new swapdevice. You may also specify the offset in the kernel image to change. Note that rdev -s is a
synonym for swapdev.

Option
-o offset
Synonymous to specifying an offset as an argument.

swapoff swapoff -a | device ...
System administration command. Stop making the listed devices available for swapping and paging.
Option
-a
Consult /etc/ fstab for devices marked sw. Use those in place of the device argument.

swapon swapon [options] device ...
System administration command. Make the listed devices available for swapping and paging.
Options
-a
Consult /etc/ fstab for devices marked sw. Use those in place of the device argument.
-p priority
Specify a priority for the swap area. Higher priority areas will be used up before lower priority areas are
used.

sync sync
System administration command. Write filesystem buffers to disk. sync executes the sync() system call. If the
system is to be stopped, sync must be called to ensure filesystem integrity. Note that shutdown automatically
calls sync before shutting down the system. sync may take several seconds to complete, so the system should be
told to sleep briefly if you are about to manually call halt or reboot. Note that shutdown is the preferred way to
halt or reboot your system, since it takes care of sync-ing and other housekeeping for you.

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sysklogd sysklogd
System administration command. sysklogd, the Linux program that provides syslogd functionality, behaves
exactly like the BSD version of syslogd. The difference should be completely transparent to the user. However,
sysklogd is coded very differently and supports a slightly extended syntax. It is invoked as syslogd. See also
klogd.

Options
-d
Turn on debugging.
-f configfile
Specify alternate configuration file.
-h
Forward messages from remote hosts to forwarding hosts.
-l hostlist
Specify hostnames that should be logged with just their hostname, not their fully qualified domain name.
Multiple hosts should be separated with a colon (:).

-m markinterval
Select number of minutes between mark messages.
-n
Avoid autobackgrounding. This is needed when starting syslogd from init.
-p socket
Send log to socket instead of /dev/ log.
-r
Receive messages from the network using an Internet domain socket with the syslog service.
-s domainlist
Strip off domain names specified in domainlist before logging. Multiple domain names should be
separated by a colon (:).

syslogd syslogd
TCP/ IP command. Log system messages into a set of files described by the configuration file /etc/ syslog. conf.
Each message is one line. A message can contain a priority code, marked by a number in angle braces at the
beginning of the line. Priorities are defined in <sys/ syslog. h>. syslogd reads from an Internet domain socket
specified in /etc/ services. To bring syslogd down, send it a terminate signal.

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systat systat [options] host
System administration command. Get information about the network or system status of a remote host by
querying its netstat, systat, or daytime service.

Options
-n, --netstat
Specifically query the host's netstat service.
-p port, --port port
Specify port to query.
-s, --systat
Specifically query the host's systat service.
-t, --time
Specifically query the host's daytime service.

tac tac [options] [file]
Named for the common command cat, tac prints files in reverse. Without a filename or with -, it reads from
standard input. By default, it reverses the order of the lines, printing the last line first.

Options
-b, --before
Print separator (by default a newline) before string that it delimits.
-r, --regex
Expect separator to be a regular expression.
-s string, --separator= string
Specify alternate separator (default is newline).
--help
Print a help message and then exit.
--version
Print version information and then exit.

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tail tail [options] [file]
Print the last 10 lines of the named file (or standard input if -is specified) on standard output.
Options
-n[ k]
Begin printing at nth item from end-of-file. k specifies the item to count: l (lines, the default), b (blocks),
or c (characters).

-k
Same as -n, but use the default count of 10.
+n[ k]
Like -n, but start at nth item from beginning of file.
+k
Like -k, but count from beginning of file.
-c num{ bkm}, --bytes num{ bkm}
Print last num bytes. An alternate blocksize may be specified:
b
512 bytes
k
1 kilobyte
m
1 megabyte
-f
Don't quit at the end of file; "follow" file as it grows. End when user presses Ctrl-C.
-n num, --lines num
Print last num lines.
-q, --quiet, --silent
Suppress filename headers.
--version
Print version information and then exit.
Examples
Show the last 20 lines containing instances of .Ah:
grep '\. Ah' file | tail -20

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Show the last 10 characters of variable name:
echo "$ name" | tail -cPrint the last two blocks of bigfile:
tail -2b bigfile

talk talk person [ttyname]
Talk to another user. person is either the login name of someone on your own machine or user@ host on another
host. To talk to a user who is logged in more than once, use ttyname to indicate the appropriate terminal name.
Once communication has been established, the two parties may type simultaneously, with their output appearing
in separate windows. To redraw the screen, type Ctrl-L. To exit, type your interrupt character; talk then moves
the cursor to the bottom of the screen and restores the terminal.

talkd talkd [option]
TCP/ IP command. Remote user communication server. talkd notifies a user that somebody else wants to initiate
a conversation. A talk client initiates a rendezvous by sending a CTL_ MSG of type LOOK_ UP to the server.
This causes the server to search its invitation tables for an existing invitation for the client. If the lookup fails,
the caller sends an ANNOUNCE message, causing the server to broadcast an announcement on the callee's login
ports requesting contact. When the callee responds, the local server responds with the rendezvous address, and a
stream connection is established through which the conversation takes place.

Option
-d
Write debugging information to the syslogd log file.

tar tar [options] [tarfile] [other-files]
Copy files to or restore files from an archive medium. If any files are directories, tar acts on the entire subtree.
Options need not be preceded by -(though they may be). The exception to this rule is when you are using a long-style
option (such as --modification-time). In that case, the exact syntax is:

tar --long-option -function-options filesFor example:
tar --modification-time -xvf tarfile. tarFunction options
You must use exactly one of these, and it must come before any other options:
-c, --create
Create a new archive.
-d, --compare
Compare the files stored in tarfile with other-files. Report any differences: missing files, different sizes,
different file attributes (such as permissions or modification time).

-r, --append

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Append other-files to the end of an existing archive.

-t, --list
Print the names of other-files if they are stored on the archive (if other-files are not specified, print names
of all files).

-u, --update
Add files if not in the archive or if modified.
-x, --extract, --get
Extract other-files from an archive (if other-files are not specified, extract all files).
-A, --catenate, --concatenate
Concatenate a second tar file on to the end of the first.
Options
n
Select device n, where n is 0,..., 9999. The default is found in /etc/ default/ tar.
[drive][ density]
Set drive (0-7) and storage density (l, m, or h, corresponding to low, medium, or high).
--atime-preserve
Preserve original access time on extracted files.
-b, --block-size= n
Set block size to n � 512 bytes.
--checkpoint
List directory names encountered.
--exclude= file
Remove file from any list of files.
-f arch, --file= filename
Store files in or extract files from archive arch. Note that filename may take the form hostname: filename.
--force-local
Interpret filenames in the form hostname: filename as local files.
-g, --listed-incremental
Create new-style incremental backup.
-h, --dereference
Dereference symbolic links.

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-i, --ignore-zeros

Ignore zero-sized blocks (i. e., EOFs).
--ignore-failed-read
Ignore unreadable files to be archived. Default behavior is to exit when encountering these.
-k, --keep-old-files
When extracting files, do not overwrite files with similar names. Instead, print an error message.
-l, --one-file-system
Do not archive files from other file systems.
-m, --modification-time
Do not restore file modification times; update them to the time of extraction.
--null
Allow filenames to be null-terminated with -T. Override -C.
--old, --portability, --preserve
Equivalent to invoking both the -p and -s options.
-p, --same-permissions, --preserve-permissions
Keep ownership of extracted files same as that of original permissions.
--remove-files
Remove originals after inclusion in archive.
--rsh-command= command
Do not connect to remote host with rsh; instead, use command.
-s, --same-order, --preserve-order
When extracting, sort filenames to correspond to the order in the archive.
--totals
Print byte totals.
--use-compress-program= program
Compress archived files with program, or uncompress extracted files with program.
-v, --verbose
Verbose. Print filenames as they are added or extracted.
-w, --interactive
Wait for user confirmation (y) before taking any actions.

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-z, --gzip, --ungzip

Compress files with gzip before archiving them, or uncompress them with gunzip before extracting them.
-C, --directory= directory
cd to directory before beginning tar operation.
-F, --info-script, --new-volume-script= script
Implies -M (multiple archive files). Run script at the end of each file.
-G, --incremental
Create old-style incremental backup.
-K file, --starting-file file
Begin tar operation at file file in archive.
-L, --tape-length= length
Write a maximum of length � 1024 bytes to each tape.
-M, --multivolume
Expect archive to multivolume. With -c, create such an archive.
-N date, --after-date date
Ignore files older than date.
-O, --to-stdout
Print extracted files on standard out.
-P, --absolute-paths
Do not remove initial slashes (/) from input filenames.
-R, --record-number
Display archive's record number.
-S, --sparse
Treat short file specially and more efficiently.
-T filename, --files-from filename
Consult filename for files to extract or create.
-V name, --label= name
Name this volume name.
-W, --verify
Check archive for corruption after creation.
-X file, --exclude file
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Consult file for list of files to exclude.
-Z, --compress, --uncompress
Compress files with compress before archiving them, or uncompress them with uncompress before
extracting them.

Examples
Create an archive of /bin and /usr/ bin (c), show the command working (v), and store on the tape in /dev/ rmt0:
tar cvf /dev/ rmt0 /bin /usr/ binList the tape's contents in a format like ls -l:
tar tvf /dev/ rmt0Extract the /bin directory:
tar xvf /dev/ rmt0 /binCreate an archive of the current directory and store it in a file backup. tar:
tar cvf -`find . -print > backup. tar(The -tells tar to store the archive on standard output, which is then redirected.)

tcpd tcpd
TCP/ IP command. Monitor incoming TCP/ IP requests (such as those for telnet, ftp, finger, exec, rlogin).
Provide checking and logging services; then pass the request to the appropriate daemon.

tcpdchk tcpdchk [options]
TCP/ IP command. Consult the TCP wrapper configuration (in /etc/ hosts. allow and /etc/ hosts. deny); display a list
of all possible problems with it; attempt to suggest possible fixes.

Options
-a
Include a list of rules; do not require an ALLOW keyword before allowing sites to access the local host.
-d
Consult ./ hosts. allow and ./ hosts. deny instead of /etc/ hosts. allow and /etc/ hosts. deny.
-i conf-file
Specify location of inetd. conf or tlid. conf file. These are files that tcpdchk automatically uses in its
evaluation of TCP wrapper files.

-v
Verbose mode.

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tcpdmatch tcpdmatch [options] daemon client
TCP/ IP command. Predict the TCP wrapper's response to a specific request. You must specify which daemon the
request is made to (the syntax may be daemon@ host for requests to remote machines) and the client from which
the request originates (the syntax may be user@ client for a specific user or a wildcard). Consult /etc/ hosts. allow
and /etc/ hosts. deny to determine the TCP wrapper's actions.

Options
-d
Consult ./ hosts. allow and ./ hosts. deny instead of /etc/ hosts. allow and /etc/ hosts. deny.
-i conf-file
Specify location of inetd. conf or tlid. conf file. These are files that tcpdmatch automatically uses in its
evaluation of TCP wrapper files.

tcsh tcsh [options] [file [arguments]]
An extended version of the C shell, a command interpreter into which all other commands are entered. For more
information, see Chapter 8, "csh and tcsh".

tee tee [options] files
Accept output from another command and send it both to the standard output and to files (like a T or fork in a
road).

Options
-a, --append
Append to files; do not overwrite.
-i, --ignore-interrupts
Ignore interrupt signals.
--help
Print a help message and then exit.
--version
Print version information and then exit.
Example
ls -l | tee savefile View listing and save for later

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telinit telinit [option] [runlevel]
System administration command. Signal init to change the system's runlevel. telinit is actually just a link to init,
the ancestor of all processes.

Option
-t seconds
Send SIGKILL seconds after SIGTERM. Default is 20.
Runlevels
The default runlevels vary from distribution to distribution, but these are standard:
0
Halt the system.
1, s, S
Single user.
6
Reboot the system.
a, b, c
Process only entries in /etc/ inittab that are marked with run level a, b, or c.
q, Q
Reread /etc/ inittab.
Check the /etc/ inittab file for runlevels on your system.

telnet telnet [options] [host [port ]]
Access remote systems. telnet is the user interface that communicates with another host using the Telnet
protocol. If telnet is invoked without host, it enters command mode, indicated by its prompt, telnet>, and
accepts and executes the commands listed after the following options. If invoked with arguments, telnet
performs an open command (shown in the following list) with those arguments. host indicates the host's official
name. port indicates a port number (default is the Telnet port).

Options
-a
Automatic login into the remote system.
-d
Turn on socket-level debugging.
-e [escape_ char]
Set initial telnet escape character to escape_ char. If escape_ char is omitted, there will be no predefined
escape character.

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-l user

When connecting to remote system and if remote system understands ENVIRON, send user to the remote
system as the value for variable USER.

-n tracefile
Open tracefile for recording the trace information.
-r
Emulate rlogin: the default escape character is a tilde (~); an escape character followed by a dot causes
telnet to disconnect from the remote host; a ^Z instead of a dot suspends telnet; and a ] (the default
telnet escape character) generates a normal telnet prompt. These codes are accepted only at the
beginning of a line.

-8
Request 8-bit operation.
-E
Disable the escape character functionality.
-L
Specify an 8-bit data path on output.
-S tos
Set the IP type-of-service (TOS) option for the Telnet connection to the value tos.
Commands
CTRL-Z
Suspend telnet.
! [command]
Execute a single command in a subshell on the local system. If command is omitted, an interactive
subshell will be invoked.

? [command]
Get help. With no arguments, print a help summary. If a command is specified, print the help information
for just that command.

close
Close a Telnet session and return to command mode.
display argument ...
Display all, or some, of the set and toggle values.
environ [arguments [...]]
Manipulate variables that may be sent through the TELNET ENVIRON option. Valid arguments for
environ are:

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?

Get help for the environ command.
define variable value
Define variable to have a value of value.
undefine variable
Remove variable from the list of en vi ronment variables.
export variable
Mark variable to have its value exported to the remote side.
unexport variable
Mark variable to not be exported unless explicitly requested by the remote side.
list
Display current variable values.
logout
If the remote host supports the logout command, close the telnet session.
mode [type]
Depending on state of Telnet session, type is one of several options:
?
Print out help information for the mode command.
character
Disable TELNET LINEMODE option, or, if remote side does not understand the option, enter
"character-at-a-time" mode.

[-] edit
Attempt to [disable] enable the EDIT mode of the TELNET LINEMODE option.
[-] isig
Attempt to [disable] enable the TRAPSIG mode of the LINEMODE option.
line
Enable LINEMODE option, or, if remote side does not understand the option, attempt to enter
"old line-by-line" mode.

[-] softtabs
Attempt to [disable] enable the SOFT_ TAB mode of the LINEMODE option.
[-] litecho
[Disable] enable LIT_ ECHO mode.

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open[-l user] host [port]
Open a connection to the named host. If no port number is specified, attempt to contact a Telnet server at
the default port.

quit
Close any open Telnet session and then exit telnet.
status
Show current status of telnet. This includes the peer one is connected to as well as the current mode.
send arguments
Send one or more special character sequences to the remote host. Following are the arguments that may
be specified:

?
Print out help information for send command.
abort
Send Telnet ABORT sequence.
ao
Send Telnet AO sequence, which should cause the remote system to flush all output from the
remote system to the user's terminal.

ayt
Send Telnet AYT (Are You There) sequence.
brk
Send Telnet BRK (Break) sequence.
do cmd
dont cmd
will cmd
wont cmd

Send Telnet DO cmd sequence, where cmd is a number between 0 and 255 or a symbolic name for
a specific telnet command. If cmd is ? or help, this command prints out help (including a list of
symbolic names).

ec
Send Telnet EC (Erase Character) sequence, which causes the remote system to erase the last
character entered.

el
Send Telnet EL (Erase Line) sequence, which causes the remote system to erase the last line
entered.

eof

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Send Telnet EOF (End Of File) sequence.

eor
Send Telnet EOR (End Of Record) sequence.
escape
Send current Telnet escape character (initially ^).
ga
Send Telnet GA (Go Ahead) sequence.
getstatus
If the remote side supports the Telnet STATUS command, getstatus sends the subnegotiation
request that the server send its current option status.

ip
Send Telnet IP (Interrupt process) sequence, which causes the remote system to abort the currently
running process.

nop
Send Telnet NOP (No operation) sequence.
susp
Send Telnet SUSP (Suspend process) sequence.
synch
Send Telnet SYNCH sequence, which causes the remote system to discard all previously typed
(but not read) input.

set argument value
unset argument value

Set any one of a number of telnet variables to a specific value or to TRUE. The special value off disables
the function associated with the variable. unset disables any of the specified functions. The values of
variables may be interrogated with the aid of the display command. The variables that may be specified
are:

?
Display legal set and unset commands.
ayt
If telnet is in LOCALCHARS mode, this character is taken to be the alternate AYT character.
echo
This is the value (initially ^E) which, when in "line-by-line" mode, toggles between doing local
echoing of entered characters and suppressing echoing of entered characters.

eof
If telnet is operating in LINEMODE or in the old "line-by-line" mode, entering this character as

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the first character on a line will cause the character to be sent to the remote system.

erase
If telnet is in LOCALCHARS mode and operating in the "character-at-a-time" mode, then when
this character is entered, a Telnet EC sequence will be sent to the remote system.

escape
This is the Telnet escape character (initially ^[), which causes entry into the Telnet command
mode when connected to a remote system.

flushoutput
If telnet is in LOCALCHARS mode and the flushoutput character is entered, a Telnet AO
sequence is sent to the remote host.

forw1
If Telnet is in LOCALCHARS mode, this character is taken to be an alternate end-of-line
character.

forw2
If Telnet is in LOCALCHARS mode, this character is taken to be an alternate end-of-line
character.

interrupt
If Telnet AO is in LOCALCHARS mode and the interrupt character is entered, a Telnet IP
sequence is sent to the remote host.

kill
If Telnet IP is in LOCALCHARS mode and operating in the "character-at-a-time" mode, then
when this character is entered, a Telnet EL sequence is sent to the remote system.

lnext
If Telnet EL is in LINEMODE or in the old "line-by-line" mode, then this character is taken to be
the terminal's lnext character.

quit
If Telnet EL is in LOCALCHARS mode and the quit character is entered, a Telnet BRK sequence
is sent to the remote host.

reprint
If Telnet BRK is in LINEMODE or in the old "line-by-line" mode, this character is taken to be the
terminal's reprint character.

rlogin
Enable rlogin mode. Same as using -r command-line option.
start
If the Telnet TOGGLE-FLOW-CONTROL option has been enabled, this character is taken to be
the terminal's start character.

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stop

If the Telnet TOGGLE-FLOW-CONTROL option has been enabled, this character is taken to be
the terminal's stop character.

susp
If Telnet is in LOCALCHARS mode, or if the LINEMODE is enabled and the suspend character
is entered, a Telnet SUSP sequence is sent to the remote host.

tracefile
File to which output generated by netdata is written.
worderase
If Telnet BRK is in LINEMODE or in the old "line-by-line" mode, this character is taken to be the
terminal's worderase character. Defaults for these are the terminal's defaults.

slc [state]
Set state of special characters when Telnet LINEMODE option has been enabled.
?
List help on the slc command.
check
Verify current settings for current special characters. If discrepancies are discovered, convert local
settings to match remote ones.

export
Switch to local defaults for the special characters.
import
Switch to remote defaults for the special characters.
toggle arguments [...]
Toggle various flags that control how Telnet responds to events. The flags may be set explicitly to true or
false using the set and unset commands listed previously. The valid arguments are:

?
Display legal toggle commands.
autoflush
If autoflush and LOCALCHARS are both true, then when the ao or quit characters are
recognized, Telnet refuses to display any data on the user's terminal until the remote system
acknowledges that it has processed those Telnet sequences.

autosynch
If autosynch and LOCALCHARS are both true, then when the intr or quit character is entered,
the resulting Telnet sequence sent is followed by the Telnet SYNCH sequence. Initial value for
this toggle is false.

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binary

Enable or disable the Telnet BINARY option on both the input and the output.
inbinary
Enable or disable the Telnet BINARY option on the input.
outbinary
Enable or disable the Telnet BINARY option on the output.
crlf
If this toggle value is true, carriage returns are sent as CR-LF. If false, carriage returns are sent as
CR-NUL. Initial value is false.

crmod
Toggle carriage return mode. Initial value is false.
debug
Toggle socket level debugging mode. Initial value is false.
localchars
If the value is true, flush, interrupt, quit, erase, and kill characters are recognized locally, then
transformed into appropriate Telnet control sequences. Initial value is true.

netdata
Toggle display of all network data. Initial value is false.
options
Toggle display of some internal telnet protocol processing pertaining to Telnet options. Initial
value is false.

prettydump
When netdata is enabled, and if prettydump is enabled, the output from the netdata command is
reorganized into a more user-friendly format, spaces are put between each character in the output,
and an asterisk precedes any Telnet escape sequence.

skiprc
Toggle whether to process ~/. telnetrc file. Initial value is false, meaning the file is processed.
termdata
Toggle printing of hexadecimal terminal data. Initial value is false.
z
Suspend telnet; works only for the csh.

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telnetd telnetd [options]
TCP/ IP command. Telnet protocol server. telnetd is invoked by the Internet server for requests to connect to the
Telnet port (port 23 by default). telnetd allocates a pseudoterminal device for a client, thereby creating a login
process that has the slave side of the pseudoterminal serving as stdin, stdout, and stderr. telnetd manipulates
the master side of the pseudoterminal by implementing the Telnet protocol and by passing characters between
the remote client and the login process.

Options
-debug [port]
Start telnetd manually instead of through inetd. port may be specified as an alternate TCP port number
on which to run telnetd.

-D modifier( s)
Debugging mode. This allows telnet to print out debugging information to the connection, enabling the
user to see what telnet is doing. Several modifiers are available for the debugging mode:

exercise
Has not been implemented yet.
netdata
Display data stream received by telnetd.
options
Print information about the negotiation of the Telnet options.
ptydata
Display data written to the pseudo terminal device.
report
Print options information, as well as some additional information about what processing is going
on.

test test expression
[expression]
Also exists as a built-in in most shells.
Evaluate an expression and, if its value is true, return a zero exit status; otherwise, return a nonzero exit status.
In shell scripts, you can use the alternate form [expression]. This command is generally used with conditional
constructs in shell programs.

File testers
The syntax for all of these options is test option file. If the specified file does not exist, they return false.
Otherwise, they will test the file as specified in the option description.

-b
Is the file block special?

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-c

Is the file character special?
-d
Is the file a directory?
-e
Does the file exist?
-f
Is the file a regular file?
-g
Does the file have the set-group-ID bit set?
-k
Does the file have the sticky bit set?
-L
Is the file a symbolic link?
-p
Is the file a named pipe?
-r
Is the file readable by the current user?
-s
Is the file nonempty?
-S
Is the file a socket?
-t [file-descriptor]
Is the file associated with file-descriptor (or 1, standard output, by default) connected to a terminal?
-u
Does the file have the set-user-ID bit set?
-w
Is the file writable by the current user?
-x
Is the file executable?
-O
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Is the file owned by the process's effective user ID?
-G
Is the file owned by the process's effective group ID?
File comparisons
The syntax for file comparisons is test file1 option file2. A string by itself, without options, returns true if it's at
least one character long.

-nt
Is file1 newer than file2? Check modification, not creation, date.
-ot
Is file1 older than file2? Check modification, not creation, date.
-ef
Do the files have identical device and inode numbers?
String tests
The syntax for string tests is test option string.
-z
Is the string 0 characters long?
-n
Is the string at least 1 character long?
= string
Are the two strings equal?
!= string
Are the strings unequal?
Expression tests
Note that an expression can consist of any of the previous tests.
! expression
Is the expression false?
expression -a expression
Are the expressions both true?
expression -o expression
Is either expression true?

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Integer tests

The syntax for integer tests is test integer1 option integer2. You may substitute -l string for an integer; this
evaluates to string's length.

-eq
Are the two integers equal?
-ne
Are the two integers unequal?
-lt
Is integer1 less than integer2?
-le
Is integer1 less than or equal to integer2?
-gt
Is integer1 greater than integer2?
-ge
Is integer1 greater than or equal to integer2?

tftp tftp [host [port]]
User interface to the TFTP (Trivial File Transfer Protocol), which allows users to transfer files to and from a
remote machine. The remote host may be specified, in which case tftp uses host as the default host for future
transfers.

Commands
Once tftp is running, it issues the prompt:
tftp>and recognizes the following commands:
? [command-name...]
Print help information.
ascii
Shorthand for mode ASCII.
binary
Shorthand for mode binary.
connect hostname [port]
Set the hostname, and optionally the port, for transfers.
get filename

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get remotename localname
get filename1 filename2 filename3... filenameN

Get a file or set of files from the specified remote sources.
mode transfer-mode
Set the mode for transfers. transfer-mode may be ASCII or binary. The default is ASCII.
put filename
put localfile remotefile
put filename1 filename2... filenameN remote-directory

Transfer a file or set of files to the specified remote file or directory.
quit
Exit tftp.
rexmt retransmission-timeout
Set the per-packet retransmission timeout, in seconds.
status
Print status information: whether tftp is connected to a remote host (i. e., whether a host has been
specified for the next connection), the current mode, whether verbose and tracing modes are on, and the
values for retransmission timeout and total transmission timeout.

timeout total-transmission-timeout
Set the total transmission timeout, in seconds.
trace
Toggle packet tracing.
verbose
Toggle verbose mode.

tftpd tftpd [homedir]
TCP/ IP command. Trivial File Transfer Protocol server. tftpd is normally started by inetd and operates at the
port indicated in the tftp Internet service description in the /etc/ inetd. conf file. By default, the entry for tftpd in
/etc/ inetd. conf is commented out; the comment character must be deleted to make tfptd operational. Before
responding to a request, the server attempts to change its current directory to homedir; the default value is
tftpboot.

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tload tload [options] [tty]
Display system load average in graph format. If tty is specified, print it to that tty.
Options
-d delay
Specify the delay, in seconds, between updates.
-s scale
Specify scale (number of characters between each graph tick). A smaller number results in a larger scale.

top top [options]
Provide information (frequently refreshed) about the most CPU-intensive processes currently running. See ps for
explanations of the field descriptors.

Options
-b
Run in batch mode; don't accept command-line input. Useful for sending output to another command or
to a file.

-c
Show command line in display instead of just command name.
-d delay
Specify delay between refreshes.
-i
Suppress display of idle and zombie processes.
-n num
Update display num times, then exit.
-p pid
Monitor only processes with the specified process ID.
-q
Refresh without any delay. If user is privileged, run with highest priority.
-s
Secure mode. Disable some (dangerous) interactive commands.
-S
Cumulative mode. Print total CPU time of each process, including dead child processes.
Interactive commands

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space

Update display immediately.
c
Toggle display of command name or full command line.
f, F
Add fields to display or remove fields from the display.
h, ?
Display help about commands and the status of secure and cumulative modes.
k
Prompt for process ID to kill and signal to send (default is 15) to kill it.
i
Toggle suppression of idle and zombie processes.
l
Toggle display of load average and uptime information.
m
Toggle display of memory information.
n, #
Prompt for number of processes to show. If 0 is entered, show as many as will fit on the screen (default).
o, O
Change order of displayed fields.
q
Exit.
r
Apply renice to a process. Prompt for PID and renice value. Suppressed in secure mode.
s
Change delay between refreshes. Prompt for new delay time, which should be in seconds. Suppressed in
secure mode.

t
Toggle display of processes and CPU states information.
A
Sort by age, with newest first.

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^L
Redraw screen.
M
Sort tasks by resident memory usage.
N
Sort numerically by process ID.
P
Sort tasks by CPU usage (default).
S
Toggle cumulative mode. (See the -S option.)
T
Sort tasks by time/ cumulative time.
W
Write current setup to ~/. toprc. This is the recommended way to write a top configuration file.

touch touch [options] files
For one or more files, update the access time and modification time (and dates) to the current time and date.
touch is useful in forcing other commands to handle files a certain way; e. g., the operation of make, and
sometimes find, relies on a file's access and modification time. If a file doesn't exist, touch creates it with a
filesize of 0.

Options
-a, --time= atime, --time= access, --time= use
Update only the access time.
-c, --no-create
Do not create any file that doesn't already exist.
-d time, --date time
Change the time value to the specified time instead of the current time. time can use several formats and
may contain month names, time zones, a. m. and p. m. strings, as well as others.

-m, --time= mtime, --time= modify
Update only the modification time.
-r file, --reference file
Change times to be the same as those of the specified file, instead of the current time.
-t time

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Use the time specified in time instead of the current time. This argument must be of the format:
[[ cc] yy] mmddhhmm[. ss], indicating optional century and year, month, date, hours, minutes, and optional
seconds.

--help
Print help message and then exit.
--version
Print the version number and then exit.

tr tr [options] [string1 [string2]]
Translate characters --copy standard input to standard output, substituting characters from string1 to string2 or
deleting characters in string1.

Options
-c, --complement
Complement characters in string1 with respect to ASCII 001-377.
-d, --delete
Delete characters in string1 from output.
-s, --squeeze-repeats
Squeeze out repeated output characters in string2.
-t, --truncate-set1
Truncate string1 to the length of string2 before translating.
--help
Print help message and then exit.
--version
Print the version number and then exit.
Special characters
Include brackets ([]) where shown.
\a
^G (bell)
\b
^H (backspace)
\f
^L (form feed)
\n

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^J (newline)
\r
^M (carriage return)
\t
^I (tab)
\v
^K (vertical tab)
\nnn
Character with octal value nnn.
\\
Literal backslash.
char1-char2
All characters in the range char1 through char2. If char1 does not sort before char2, produce an error.
[char1-char2]
Same as char1-char2 if both strings use this.
[char*]
In string2, expand char to the length of string1.
[char* number]
Expand char to number occurrences. [x* 4] expands to xxxx, for instance.
[: class:]
Expand to all characters in class, where class can be:
alnum
Letters and digits
alpha
Letters
blank
Whitespace
cntrl
Control characters
digit

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Digits

graph
Printable characters except space
lower
Lowercase letters
print
Printable characters
punct
Punctuation
space
Whitespace (horizontal or vertical)
upper
Uppercase letters
xdigit
Hexadecimal digits
[= char=]
The class of characters in which char belongs.
Examples
Change uppercase to lowercase in a file:
cat file | tr '[ A-Z] ' '[ a-z] 'Turn spaces into newlines (ASCII code 012):
tr ' ' '\ 012' < fileStrip blank lines from file and save in new. file (or use 011 to change successive tabs into one tab):
cat file | tr -s "" "\ 012" > new. fileDelete colons from file; save result in new. file:
tr -d : < file > new. file

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traceroute traceroute [options] host [packetsize]
TCP/ IP command. Trace route taken by packets to reach network host. traceroute attempts tracing by launching
UDP probe packets with a small TTL (time to live), then listening for an ICMP "time exceeded" reply from a
gateway. host is the destination hostname or the IP number of host to reach. packetsize is the packet size in bytes
of the probe datagram. Default is 38 bytes.

Options
-d
Turn on socket-level debugging.
-g addr
Enable the IP LSRR (Loose Source Record Route) option in addition to the TTL tests, to ask how
someone at IP address addr can reach a particular target.

-l
Include the time-to-live value for each packet received.
-m max_ ttl
Set maximum time-to-live used in outgoing probe packets to max-ttl hops. Default is 30 hops.
-n
Show numerical addresses; do not look up hostnames. (Useful if DNS is not functioning properly.)
-p port
Set base UDP port number used for probe packets to port. Default is (decimal) 33434.
-q n
Set number of probe packets for each time-to-live setting to the value n. Default is 3.
-r
Bypass normal routing tables and send directly to a host on an attached network.
-s src_ addr
Use src_ addr as the IP address that will serve as the source address in outgoing probe packets.
-t tos
Set the type-of-service in probe packets to tos (default 0). The value must be a decimal integer in the
range 0 to 255.

-v
Verbose --received ICMP packets (other than TIME_ EXCEEDED and PORT_ UNREACHABLE) will
be listed.

-w wait
Set time to wait for a response to an outgoing probe packet to wait seconds (default is 3 seconds).

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troff troff
See groff.

true true
A null command that returns a successful (0) exit status. See also false.

tune2fs tune2fs [options] device
System administration command. Tune the parameters of a Linux Second Extended Filesystem by adjusting
various parameters. You must specify the device on which the filesystem resides; it must not be mounted
read/ write when you change its parameters.

Options
-c mount-counts
Specify the maximum number of mount counts between two checks on the filesystem.
-e behavior
Specify the kernel's behavior when encountering errors. behavior must be one of:
continue
Continue as usual.
remount-ro
Remount the offending filesystem in read-only mode.
panic
Cause a kernel panic.
-g group
Allow group (a group ID or name) to use reserved blocks.
-i interval[ d| w| m]
Specify the maximum interval between filesystem checks. Units may be in days (d), weeks (w), or
months (m). If interval is 0, checking will not be time-dependent.

-l
Display a list of the superblock's contents.
-m percentage
Specify the percentage of blocks that will be reserved for use by privileged users.
-r num
Specify the number of blocks that will be reserved for use by privileged users.
-u user

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Allow user (a user ID or name) to use reserved blocks.

tunelp tunelp device [options]
System administration command. Control a lineprinter's device parameters. Without options, print information
about device( s).

Options
-a [on| off]
Specify whether or not to abort if the printer encounters an error. By default, do not abort.
-c n
Retry device n times if it refuses a character. (Default is 250.) After exhausting n, sleep before retrying.
-i irq
Use irq for specified parallel port. Ignore -t and -c. If 0, restore noninterrupt driven (polling) action.
-o [on| off]
Specify whether to abort if device is not online or is out of paper.
-q [on| off]
Specify whether to print current IRQ setting.
-r
Reset port.
-s
Display printer's current status.
-t time
Specify a delay of time in jiffies to sleep before resending a refused character to the device. A jiffy is
defined as either one tick of the system clock or one AC cycle time; it should be approximately 1/ 100th
of a second.

-w time
Specify a delay of time in jiffies to sleep before resending a strobe signal.
-C [on| off]
Specify whether to be extremely careful in checking for printer error.

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ul ul [options] [names]
Translate underscores to underlining. The correct sequence with which to do this will vary by terminal type.
Some terminals are unable to handle underlining.

Options
-i
Translate -, when on a separate line, to underline, instead of translating underscores.
-t terminal-type
Specify terminal type. By default, TERM is consulted.

umount umount [options] [special-device/ directory]
System administration command. Unmount a filesystem. umount announces to the system that the removable
file structure previously mounted on device special-device is to be removed. umount also works by specifying
the directory. Any pending I/ O for the filesystem is completed, and the file structure is flagged as clean.

Options
-a
Unmount all filesystems that are listed in /etc/ mtab.
-n
Unmount, but do not record changes in /etc/ mtab.
-t type
Unmount only filesystems of type type.

uname uname [options]
Print information about the machine and operating system. Without options, print the name of the operating
system (Linux).

Options
-a, --all
Combine all the system information from the other options.
-m, --machine

Print the hardware the system is running on.
-n, --nodename

Print the machine's hostname.
-r, --release

Print the release number of the kernel.
-s, --sysname

Print the name of the operating system (Linux).
-p, --processor

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Print the type of processor (not available on all versions).
-v

Print build information about the kernel.
--help

Display a help message and then exit.
--version

Print version information and then exit.

uncompress uncompress [options] files
Uncompress files that were compressed (i. e., whose names end in .Z). See compress for the available options;
uncompress takes all the same options except -r and -b.

unexpand unexpand [options] [files]
Convert strings of initial whitespace, consisting of at least two spaces and/ or tabs to tabs. Read from standard
input if given no file or a file named -.

Options
-a, --all
Convert all, not just initial, strings of spaces and tabs.
-nums, -t nums, --tabs nums
nums is a comma-separated list of integers that specify the placement of tab stops. If a single integer is
provided, the tab stops are set to every integer spaces. By default, tab stops are 8 spaces apart. With -t
and --tabs, the list may be separated by whitespace instead of commas. This option implies -a.

--help
Print help message and then exit.
--version
Print the version number and then exit.

uniq uniq [options] [file1 [file2]]
Remove duplicate adjacent lines from sorted file1, sending one copy of each line to file2 (or to standard output).
Often used as a filter. Specify only one of -d or -u. See also comm and sort.

Options
-n, -f n, --skip-fields= n
Ignore first n fields of a line. Fields are separated by spaces or by tabs.
+n, -s n, --skip-chars= n
Ignore first n characters of a field.
-c, --count
Print each line once, prefixing number of instances.

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-d, --repeated
Print duplicate lines once but no unique lines.
-i, --ignore-case
Ignore case differences when checking for duplicates.
-u, --unique
Print only unique lines (no copy of duplicate entries is kept).
-w n, --check-chars= n
Compare only first n characters per line (beginning after skipped fields and characters).
--help
Print a help message and then exit.
--version
Print version information and then exit.
Examples
Send one copy of each line from list to output file list. new:
uniq list list. newShow which names appear more than once:
sort names | uniq -d

unshar unshar [options] [files]
Unpack a shell archive (shar file). unshar scans mail messages looking for the start of a shell archive. It then
passes the archive through a copy of the shell to unpack it. unshar accepts multiple files. If no files are given,
standard input is used.

Options
-c, --overwrite
Overwrite existing files.
-d directory, --directory= directory
Change to directory before unpacking any files.
-e, --exit-0
Sequentially unpack multiple archives stored in same file; uses clue that many shar files are terminated
by an exit 0 at the beginning of a line. (Equivalent to -E "exit 0".)

-E string, --split-at= string
Like -e, but allows you to specify the string that separates archives.

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-f, --force

Same as -c.
--help
Print help message and then exit.
--version
Print the version number and then exit.

update update [options]
System administration command. update is a daemon that controls how often the kernel's disk buffers are
flushed to disk. update is also known as bdflush. The daemon forks a couple of processes to call system
functions flush() and sync(). When called by an unprivileged user, no daemon is created. Instead, update calls
sync() and then exits. By default, update will wake up every 5 seconds and flush() some dirty buffers. If that
doesn't work, it will try waking up every 30 seconds to sync() the buffers to disk. Not all of the listed options are
available in every version of update.

Options
-d
Display the kernel parameters. This does not start the update daemon.
-f seconds
Call flush() at this interval. Default is 5.
-h
Help. Print a command summary.
-s seconds
Call sync() at this interval. Default is 30.
-S
Always use sync() instead of flush.
-0 percent
Flush buffers when the specified percent of the buffer cache is dirty.
-1 blocks
The maximum number of dirty blocks to write out per wake cycle.
-2 buffers
The number of clean buffers to try to obtain each time the free buffers are refilled.
-3 blocks
Flush buffers if dirty blocks exceed blocks when trying to refill the buffers.
-4 percent

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Percent of buffer cache to scan when looking for free clusters.
-5 seconds
Time for a data buffer to age before being flushed.
-6 seconds
Time for a nondata buffer to age before being flushed.
-7 constant
The time constant to use for load average.
-8 ratio
How low the load average can be before trimming back the number of buffers.

uptime uptime
Print the current time, amount of time logged in, number of users currently logged in (which may include the
same user multiple times), and system load averages. This output is also produced by the first line of the w
command.

useradd useradd [options] [user]
System administration command. Create new user accounts or update default account information. Unless
invoked with the -D option, user must be given. useradd will create new entries in system files. Home
directories and initial files may also be created as needed.

Options
-c comment
Comment field.
-d dir
Home directory. The default is to use user as the directory name under the home directory specified with
the -D option.

-e date
Account expiration date. date is in the format MM/ DD/ YYYY. Two-digit year fields are also accepted.
The value is stored as the number of days since January 1, 1970. This option requires the use of shadow
passwords.

-f days
Permanently disable account this many days after the password has expired. A value of -1 disables this
feature. This option requires the use of shadow passwords.

-g group
Initial group name or ID number. If a different default group has not been specified using the -D option,
the default group is 1.

-G groups

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Supplementary groups given by name or number in a comma-separated list with no whitespace.

-k [dir]
Copy default files to user's home directory. Meaningful only when used with the -m option. Default files
are copied from /etc/ skel/ unless an alternate dir is specified.

-m
Make user's home directory if it does not exist. The default is not to make the home directory.
-o
Override. Accept a nonunique uid with the -u option. (Probably a bad idea.)
-s shell
Login shell.
-u uid
Numerical user ID. The value must be unique unless the -o option is used. The default value is the
smallest ID value greater than 99 and greater than every other uid.

-D [options]
Set or display defaults. If options are specified, set them. If no options are specified, display current
defaults. The options are:

-b dir
Home directory prefix to be used in creating home directories. If the -d option is not used when
creating an account, the user name will be appended to dir.

-e date
Expire date. Requires the use of shadow passwords.
-f days
Number of days after a password expires to disable an account. Requires the use of shadow
passwords.

-g group
Initial group name or ID number.
-s shell
Default login shell.

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userdel userdel [option] user
System administration command. Delete all entries for user in system account files.
Option
-r
Remove the home directory of user and any files contained in it.

usermod usermod [options] user
System administration command. Modify user account information.
Options
-c comment
Comment field.
-d dir
Home directory.
-e date
Account expiration date. date is in the format MM/ DD/ YYYY. Two-digit year fields are also accepted,
but the value is stored as the number of days since January 1, 1970. This option requires the use of
shadow passwords.

-f days
Permanently disable account this many days after the password has expired. A value of -1 disables this
feature. This option requires the use of shadow passwords.

-g group
Initial group name or number.
-G groups
Supplementary groups given by name or number in a comma-separated list with no whitespace. user will
be removed from any groups to which they currently belong that are not included in groups.

-l name
Login name. This cannot be changed while the user is logged in.
-o
Override. Accept a nonunique uid with the -u option.
-s shell
Login shell.
-u uid
Numerical user ID. The value must be unique unless the -o option is used. Any files owned by user in the
user's home directory will have their user ID changed automatically. Files outside of the home directory

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will not be changed. user should not be executing any processes while this is changed.

users users [file]
Print a space-separated list of each login session on the host. Note that this may include the same user multiple
times. Consult file or, by default, /etc/ utmp.

usleep usleep [microseconds]
usleep [options]
Sleep some number of microseconds (default is 1).
Options
--help
Print help information and then exit.
--usage
Print usage message and then exit.
-v, --version
Print version information.

uudecode uudecode [-o outfile] [file]
Read a uuencoded file and re-create the original file with the permissions and name set in the file (see
uuencode). The -o option specifies an alternate output file.

uuencode uuencode [-m] [file] name
Encode a binary file. The encoding uses only printable ASCII characters and includes the permissions and name
of the file. When file is reconverted via uudecode, the output is saved as name. If the file argument is omitted,
uuencode can take standard input, so a single argument is taken as the name to be given to the file when it is
decoded. With the -m option, base64 encoding is used.

Example
It's common to encode a file and save it with an identifying extension, such as .uue. This example encodes the
binary file flower12. jpg, names it rose. jpg, and saves it to a .uue file:

% uuencode flower12. jpg rose. jpg > rose. uueEncode flower12. jpg and mail it:
% uuencode flower12. jpg flower12. jpg | mail ellen@ oreilly. com

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vacation vacation
vacation [options] [user]
Automatically return a mail message to the sender announcing that you are on vacation.
Use vacation with no options to initialize the vacation mechanism. The process performs several steps.
1. Creates a .forward file in your home directory. The .forward file contains:
\user, "|/ usr/ bin/ vacation user"user is your login name. The action of this file is to actually deliver the mail to user (i. e., you) and to run
the incoming mail through vacation.

2. Creates the .vacation. pag and .vacation. dir files. These files keep track of who has sent you messages, so
that they receive only one "I'm on vacation" message from you per week.

3. Starts an editor to edit the contents of .vacation. msg. The contents of this file are mailed back to
whomever sends you mail. Within its body, $subject is replaced with the contents of the incoming
message's Subject line.

Remove or rename the .forward file to disable vacation processing.
Options
The -a and -r options are used within a .forward file; see the example.
-a alias
Mail addressed to alias is actually mail for the user and should produce an automatic reply.
-i
Reinitialize the .vacation. pag and .vacation. dir files. Use this right before leaving for your next vacation.
-r interval
By default, no more than one message per week is sent to any sender. This option changes that interval.
interval is a number with a trailing s, m, h, d, or w indicating seconds, minutes, hours, days, or weeks,
respectively. If interval is infinite, only one reply is sent to each sender.

Example
Send no more than one reply every three weeks to any given sender:
$ cd$ vacation -I$ cat .forward\jp, "|/ usr/ bin/ vacation -r3w jp" $cat .vacation. msgFrom: jp@ wizard-corp. com (J. Programmer, via the vacation program) Subject: I'm out of the office ...

Hi. I'm off on a well-deserved vacation after finishing up whizprog 1.0. I will read and reply to your mail regarding "$ SUBJECT" when I return.

Have a nice day.

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vi vi [options] [files]
A screen-oriented text editor based on ex. For more information on vi, see Chapter 11, "The vi Editor".

vidmode vidmode [option] image [mode [offset]]
System administration command. Sets the video mode for a kernel image. If no arguments are specified, print
current mode value. mode is a 1-byte value located at offset 506 in a kernel image. You may change the mode by
specifying the kernel image to change, the new mode, and the byte offset at which to place the new information
(the default is 506). Note that rdev -v is a synonym for vidmode. If LILO is used, vidmode is not needed. The
video mode can be set from the LILO prompt during a boot.

Modes
-3
Prompt
-2
Extended VGA
-1
Normal VGA
0
Same as entering 0 at the prompt
1
Same as entering 1 at the prompt
2
Same as entering 2 at the prompt
3
Same as entering 3 at the prompt
n
Same as entering n at the prompt
Option
-o offset
Same as specifying an offset as an argument.

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w w [options] [user]
Print summaries of system usage, currently logged-in users, and what they are doing. w is essentially a
combination of uptime, who, and ps -a. Display output for one user by specifying user.

Options
-f
Toggle printing the from (remote hostname) field.
-h
Suppress headings and uptime information.
-s
Use the short format.
-u
Ignore the username while figuring out the current process and CPU times.
-V
Display version information.
File
/var/ run/ utmp
List of users currently logged on.

wall wall [file]
System administration command. Write to all users. wall reads a message from the standard input until an end-of-file.
It then sends this message to all users currently logged in, preceded by "Broadcast Message from..." If file is
specified, read input from that, rather than from standard input.

wc wc [options] [files]
Print character, word, and line counts for each file. Print a total line for multiple files. If no files are given, read
standard input. See other examples under ls and sort.

Options
-c, -bytes, --chars
Print character count only.
-l, --lines
Print line count only.
-w, --words
Print word count only.
--help

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Print help message and then exit.
--version
Print the version number and then exit.
Examples
Count the number of users logged in:
who | wc -lCount the words in three essay files:
wc -w essay.[ 123]Count lines in the file named by variable $file (don't display filename):
wc -l < $file

whatis whatis keywords
Search the short manual page descriptions in the whatis database for each keyword and print a one-line
description to standard output for each match. Like apropos, except that it only searches for complete words.
Equivalent to man -f.

whereis whereis [options] files
Locate the binary, source, and manual page files for specified commands/ files. The supplied filenames are first
stripped of leading pathname components and any (single) trailing extension of the form .ext (for example, .c).
Prefixes of s. resulting from use of source code control are also dealt with. whereis then attempts to locate the
desired program in a list of standard Linux directories (e. g., /bin, /etc, /usr/ bin, /usr/ local/ bin/, etc.).

Options
-b
Search only for binaries.
-f
Terminate the last directory list and signal the start of filenames; required when any of the -B, -M, or -S
options are used.

-m
Search only for manual sections.
-s
Search only for sources.
-u
Search for unusual entries, that is, files that do not have one entry of each requested type. Thus, the
command whereis -m -u * asks for those files in the current directory that have no documentation.

-B directories

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Change or otherwise limit the directories to search for binaries.

-M directory
Change or otherwise limit the directories to search for manual sections.
-S directory
Change or otherwise limit the directories to search for sources.
Example
Find all files in /usr/ bin that are not documented in /usr/ man/ man1 but that have source in /usr/ src:
% cd /usr/ bin% whereis -u -M /usr/ man/ man1 -S /usr/ src -f *

which which [options] [--] [command] [...]
List the full pathnames of the files that would be executed if the named commands had been run. which searches
the user's $PATH environment variable. The C shell and tcsh have a built-in which command that has no
options. To use the options, specify the full pathname (e. g., /usr/ bin/ which).

Options
-a, --all
Print all matches, not just the first.
-i, --read-alias
Read aliases from standard input and write matches to standard output. Useful for using an alias for
which.

--skip-alias
Ignore --read-alias if present. Useful for finding normal binaries while using --read-alias in an alias for
which.

--skip-dot
Skip directories that start with a dot.
--skip-tilde
Skip directories that start with a tilde (~) and executables in $HOME.
--show-dot
If a matching command is found in a directory that starts with a dot, print ./ cmdname instead of the full
pathname.

--show-tilde
Print a tilde (~) to indicate the user's home directory. Ignored if the user is root.
--tty-only
Stop processing options on the right if not on a tty.

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-v, -V, --version

Print version information and then exit.
Example
$ which cc ls/usr/ bin/ cc ls: aliased to ls -sFC

who who [options] [file]
who am i
Show who is logged in to the system. With no options, list the names of users currently logged in, their terminal,
the time they have been logged in, and the name of the host from which they have logged on. An optional system
file (default is /etc/ utmp) can be supplied to give additional information.

Options
am i
Print the username of the invoking user.
--help
Print a help message and then exit.
-i, -u, --idle
Include idle times. An idle time of . indicates activity within the last minute; one of old indicates no
activity in more than a day.

-l, --lookup
Attempt to include canonical hostnames via DNS.
-m
Same as who am i.
-q, --count
"Quick." Display only the usernames and total number of users.
--version
Print version information and then exit.
-w, -T, --mesg, --message, --writable
Include user's message status:
+
mesg y (write messages allowed)
-mesg
n (write messages refused)

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?
Cannot find terminal device
-H, --heading
Print headings.
Example
This sample output was produced at 8 a. m. on April 17:
$ who -uHNAME LINE TIME IDLE PID COMMENTS Earvin ttyp3 Apr 16 08: 14 16: 25 2240 Larry ttyp0 Apr 17 07: 33 . 15182

Since Earvin has been idle since yesterday afternoon (16 hours), it appears that he isn't at work yet. He simply
left himself logged in. Larry's terminal is currently in use.

whoami whoami
Print current user ID. Equivalent to id -un.

write write user [tty]
message
Initiate or respond to an interactive conversation with user. A write session is terminated with EOF. If the user
is logged in to more than one terminal, specify a tty number. See also talk; use mesg to keep other users from
writing to your terminal.

xargs xargs [options] [command]
Execute command (with any initial arguments), but read remaining arguments from standard input instead of
specifying them directly. xargs passes these arguments in several bundles to command, allowing command to
process more arguments than it could normally handle at once. The arguments are typically a long list of
filenames (generated by ls or find, for example) that get passed to xargs via a pipe.

Options
-0, --null
Expect filenames to be terminated by NULL instead of whitespace. Do not treat quotes or backslashes
specially.

-e[ string], --eof[= string]
Set EOF to _ or, if specified, to string.
--help
Print a summary of the options to xargs and then exit.
-i[ string], --replace[= string]
Edit all occurrences of {}, or string, to the names read in on standard input. Unquoted blanks are not
considered argument terminators. Implies -x and -l 1.

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-l[ lines], --max-lines[= lines]
Allow no more than 1, or lines, nonblank input lines on the command line. Implies -x.
-n args, --max-args= args
Allow no more than args arguments on the command line. May be overridden by -s.
-p, --interactive
Prompt for confirmation before running each command line. Implies -t.
-P max, --max-procs= max
Allow no more than max processes to run at once. The default is 1. A maximum of 0 allows as many as
possible to run at once.

-r, --no-run-if-empty
Do not run command if standard input contains only blanks.
-s max, --max-chars= max
Allow no more than max characters per command line.
-t, --verbose
Verbose mode. Print command line on standard error before executing.
-x, --exit
If the maximum size (as specified by -s) is exceeded, exit.
--version
Print the version number of xargs and then exit.
Examples
grep for pattern in all files on the system:
find / -print | xargs grep pattern > out &Run diff on file pairs (e. g., f1. a and f1. b, f2. a and f2. b ...):
echo $* | xargs -n2 diffThe previous line would be invoked as a shell script, specifying filenames as arguments. Display file, one word
per line (same as deroff -w):

cat file | xargs -n1Move files in olddir to newdir, showing each command:
ls olddir | xargs -i -t mv olddir/{} newdir/{}

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yacc yacc [options] file
Given a file containing context-free grammar, convert file into tables for subsequent parsing and send output to
y. tab. c. This command name stands for yet another compiler-compiler. See also flex, bison, and lex & yacc by
John Levine, Tony Mason, and Doug Brown.

Options
-b prefix
Prepend prefix, instead of y, to the output file.
-d
Generate y. tab. h, producing #define statements that relate yacc's token codes to the token names declared
by the user.

-l
Exclude #line constructs from code produced in y. tab. c. (Use after debugging is complete.)
-t
Compile runtime debugging code.
-v
Generate y. output, a file containing diagnostics and notes about the parsing tables.

yes yes [strings]
yes [option]
Print the command-line arguments, separated by spaces and followed by a newline, until killed. If no arguments
are given, print y followed by a newline until killed. Useful in scripts and in the background; its output can be
piped to a program that issues prompts.

Options
--help
Print a help message and then exit.
--version
Print version information and then exit.

ypbind ypbind [options]
NFS/ NIS command. NIS binder process. ypbind is a daemon process typically activated at system startup time.
Its function is to remember information that lets client processes on a single node communicate with some
ypserv process. The information ypbind remembers is called a binding --the association of a domain name with
the Internet address of the NIS server and the port on that host at which the ypserv process is listening for
service requests. This information is cached in the file /var/ yp/ bindings/ domainname. version.

Options
-ypset

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May be used to change the binding. This option is very dangerous and should be used only for debugging
the network from a remote machine.

-ypsetme
ypset requests may be issued from this machine only. Security is based on IP address checking, which
can be defeated on networks on which untrusted individuals may inject packets. This option is not
recommended.

ypcat ypcat [options] mname
NFS/ NIS command. Print values in an NIS database specified by mname, which may be either a map name or a
map nickname.

Options
-d domain
Specify domain other than default domain.
-k
Display keys for maps in which values are null or key is not part of value.
-t
Do not translate mname to map name.
-x
Display map nickname table listing the nicknames (mnames) known and map name associated with each
nickname. Do not require an mname argument.

ypchfn ypchfn [option] [user]
NFS/ NIS command. Change your information stored in /etc/ passwd and displayed when you are fingered;
distribute the change over NIS. Without options, ypchfn enters interactive mode and prompts for changes. To
make a field blank, enter the keyword none. The superuser can change the information for any user. See also
yppasswd and ypchsh.

Options
-f
Behave like ypchfn (default).
-l
Behave like ypchsh.
-p
Behave like yppasswd.

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ypchsh ypchsh [option] [user]
NFS/ NIS command. Change your login shell and distribute this information over NIS. Warn if shell does not
exist in /etc/ shells. The superuser can change the shell for any user. See also yppasswd and ypchfn.

Options
-f
Behave like ypchfn.
-l
Behave like ypchsh (default).
-p
Behave like yppasswd.

ypinit ypinit [options]
NFS/ NIS command. Build and install an NIS database on an NIS server. ypinit can be used to set up a master or
a slave server or slave copier. Only a privileged user can run ypinit.

Options
-c master_ name
Set up a slave copier database. master_ name should be the hostname of an NIS server, either the master
server for all the maps or a server on which the database is up-to-date and stable.

-m
Indicates that the local host is to be the NIS server.
-s master_ name
Set up a slave server database. master_ name should be the hostname of an NIS server, either the master
server for all the maps or a server on which the database is up-to-date and stable.

ypmatch ypmatch [options] key... mname
NFS/ NIS command. Print value of one or more keys from an NIS map specified by mname. mname may be
either a map name or a map nickname.

Options
-d domain
Specify domain other than default domain.
-k
Before printing value of a key, print key itself, followed by a colon (:).
-t
Do not translate nickname to map name.

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-x

Display map nickname table listing the nicknames (mnames) known, and map name associated with each
nickname. Do not require an mname argument.

yppasswd yppasswd [option] [name]
NFS/ NIS command. Change login password in Network Information Service. Create or change your password,
and distribute the new password over NIS. The superuser can change the password for any user. See also ypchfn
and ypchsh.

Options
-f
Behave like ypchfn.
-l
Behave like ypchsh.
-p
Behave like yppasswd (default).

yppasswdd rpc. yppasswdd [option]
NFS/ NIS command. Server for modifying the NIS password file. yppasswdd handles password change requests
from yppasswd. It changes a password entry only if the password represented by yppasswd matches the
encrypted password of that entry and if the user ID and group ID match those in the server's /etc/ passwd file.
Then it updates /etc/ passwd and the password maps on the local server.

Option
-s
Support shadow password functions.

yppoll yppoll [options] mapname
NFS/ NIS command. Determine version of NIS map at NIS server. yppoll asks a ypserv process for the order
number and the hostname of the master NIS server for the named map.

Options
-h host
Ask the ypserv process at host about the map parameters. If host is not specified, the hostname of the
NIS server for the local host (the one returned by ypwhich) is used.

-d domain
Use domain instead of the default domain.

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yppush yppush [options] mapnames
NFS/ NIS command. Force propagation of changed NIS map. yppush copies a new version of an NIS map,
mapname, from the master NIS server to the slave NIS servers. It first constructs a list of NIS server hosts by
reading the NIS map ypservers with the -d option's domain argument. Keys within this map are the ASCII
names of the machines on which the NIS servers run. A "transfer map" request is sent to the NIS server at each
host, along with the information needed by the transfer agent to call back the yppush. When the attempt has
been completed and the transfer agent has sent yppush a status message, the results may be printed to stdout.
Normally invoked by /var/ yp/ Makefile.

Options
-d domain
Specify a domain.
-v
Verbose --print message when each server is called and for each response.

ypserv ypserv [options]
NFS/ NIS command. NIS server process. ypserv is a daemon process typically activated at system startup time. It
runs only on NIS server machines with a complete NIS database. Its primary function is to look up information
in its local database of NIS maps. The operations performed by ypserv are defined for the implementor by the
NIS protocol specification and for the programmer by the header file <rpcvc/ yp_ prot. h>. Communication to and
from ypserv is by means of RPC calls.

Options
-d
NIS service should go to the DNS for more host information.
-localonly
Indicates ypserv should not respond to outside requests.
Files and directories
/var/ yp/[ domainname]/
Location of NIS databases.
/var/ yp/ Makefile
Makefile that is responsible for creating NIS databases.

ypset ypset [options] server
NFS/ NIS command. Point ypbind at a particular server. ypset tells ypbind to get NIS services for the specified
domain from the ypserv process running on server. server indicates the NIS server to bind to and can be
specified as a name or an IP address.

Options
-d domain
Use domain instead of the default domain.

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-h host
Set ypbind's binding on host, instead of locally. host can be specified as a name or an IP address.

ypwhich ypwhich [options] [host]
NFS/ NIS command. Return hostname of NIS server or map master. Without arguments, ypwhich cites the NIS
server for the local machine. If host is specified, that machine is queried to find out which NIS master it is using.

Options
-d domain
Use domain instead of the default domain.
-m map
Find master NIS server for a map. No host can be specified with -m. map may be a map name or a
nickname for a map.

-t mapname
Inhibit nickname translation.
-x
Display map nickname table. Do not allow any other options.

ypxfr ypxfr [options] mapname
NFS/ NIS command. Transfer an NIS map from the server to the local host by making use of normal NIS
services. ypxfr creates a temporary map in the directory /etc/ yp/ domain (where domain is the default domain for
the local host), fills it by enumerating the map's entries, and fetches the map parameters and loads them. If run
interactively, ypxfr writes its output to the terminal. However, if it is invoked without a controlling terminal, and
if the log file /usr/ admin/ nislog exists, it appends all its output to that file.

Options
-b
Preserve the resolver flag in the map during the transfer.
-C tid prog ipadd port
This option is for use only by ypserv. When ypserv invokes ypxfr, it specifies that ypxfr should call
back a yppush process at the host with IP address ipadd, registered as program number prog, listening on
port port, and waiting for a response to transaction tid.

-c
Do not send a "Clear current map" request to the local ypserv process.
-d domain
Specify a domain other than the default domain.
-f
Force the transfer to occur even if the version at the master is older than the local version.

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-h host
Get the map from host, regardless of what the map says the master is. If host is not specified, ypxfr asks
the NIS service for the name of the master and tries to get the map from there. host may be a name or an
Internet address in the form h. h. h. h.

-S
Use only NIS servers running as root and using a reserved port.
-s domain
Specify a source domain from which to transfer a map that should be the same across domains (such as
the services. byname map).

zcat zcat [options] [files]
Read one or more files that have been compressed with gzip or compress and write them to standard output.
Read standard input if no files are specified or if -is specified as one of the files; end input with EOF. zcat is
identical to gunzip -c and takes the options -fhLV described for gzip/ gunzip.

zcmp zcmp [options] files
Read compressed files and pass them, uncompressed, to the cmp command, along with any command-line
options. If a second file is not specified for comparison, look for a file called file. gz.

zdiff zdiff [options] files
Read compressed files and pass them, uncompressed, to the diff command, along with any command-line
options. If a second file is not specified for comparison, look for a file called file. gz.

zdump zdump [options] [zones]
System administration command. Dump a list of all known time zones or, if an argument is provided, a specific
zone or list of zones. Include each zone's current time with its name.

Options
-c year
Specify a cutoff year to limit verbose output. Meaningful only with -v.
-v
Verbose mode. Include additional information about each zone.

zforce zforce [names]
Rename all gzipped files to filename. gz, unless file already has a .gz extension.

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zgrep zgrep [options] [files]
Uncompress files and pass to grep, along with any command-line arguments. If no files are provided, read from
(and attempt to uncompress) standard input. May be invoked as zegrep or zfgrep and will in those cases invoke
egrep or fgrep.

zic zic [options] [files]
System administration command. Create time conversion information files from the file or files specified. If the
specified file is -, read information from standard input.

Options
-d directory
Place the newly created files in directory. Default is /usr/ local/ etc/ zoneinfo.
-l timezone
Specify a timezone to use for local time. zic links the zone information for timezone with the zone
localtime.

-p timezone
Set the default rules for handling POSIX-format environment variables to the zone name specified by
timezone.

-s
Store time values only if they are the same when signed as when unsigned.
-v
Verbose mode. Include extra error checking and warnings.
-y command
Check year types with command. Default is yearistype.
-L file
Consult file for information about leap seconds.
The source file( s) for zic should be formatted as a sequence of rule lines, zone lines, and link lines. An optional
file containing leap second rules can be specified on the command line. Rule lines describe how time should be
calculated. They describe changes in time, daylight savings time, war time, and any other changes that might
affect a particular time zone. Zone lines specify which rules apply to a given zone. Link lines link similar zones
together. Leap lines describe the exact time when leap seconds should be added or subtracted. Each of these
lines is made up of fields. Fields are separated from one another by any number of whitespace characters.
Comment lines are preceded by a #. The fields used in each line are listed next.

Rule line fields
The format of a rule line is:
Rule NAME FROM TO TYPE IN ON AT SAVE LETTERSNAME
Name this set of rules.

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FROM
Specify the first year to which this rule applies. Gregorian calendar dates are assumed. Instead of
specifying an actual year, you may specify minimum or maximum for the minimum or maximum year
representable as an integer.

TO
Specify the last year to which this rule applies. Syntax is the same as for the FROM field.
TYPE
Specify the type of year to which this rule should be applied. The wildcard -instructs that all years be
included. Any given year's type will be checked with the command given with the -y option or the default
yearistype year type. An exit status of 0 is taken to mean the year is of the given type; an exit status of 1
means that it is not of the given type (see -y option).

IN
Specify month in which this rule should be applied.
ON
Specify day in which this rule should be applied. Whitespace is not allowed. For example:
1
The 1st
firstSun
The first Sunday
Sun>= 3
The first Sunday to occur before or on the 3rd
AT
Specify the time after which the rule is in effect. For example, you may use 13, 13: 00, or 13: 00: 00 for
1: 00 p. m.. You may include one of several suffixes (without whitespace between):

s
Local standard time.
u, g, z
Universal time.
w
Wall clock time (default).
SAVE
Add this amount of time to the local standard time. Formatted like AT, without suffixes.
LETTERS

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Specify letter or letters to be used in time zone abbreviations (for example, S for EST). For no
abbreviation, enter -.

Zone line fields
The format of a zone line is:
Zone NAME GMTOFF RULES/ SAVE FORMAT [UNTIL]NAME
Time zone name.
GMTOFF
The amount of hours by which this time zone differs from GMT. Formatted like AT. Negative times are
subtracted from GMT; by default, times are added to it.

RULES/ SAVE
Either the name of the rule to apply to this zone or the amount of time to add to local standard time. To
make the zone the same as local standard time, specify -.

FORMAT
How to format time zone abbreviations. Specify the variable part with %s.
UNTIL
Change the rule for the zone at this date. The next line must specify the new zone information and
therefore must omit the string "Zone" and the NAME field.

Link line fields
The format of a link line is:
Link LINK-FROM LINK-TOLINK-FROM
The name of the zone that is being linked.
LINK-TO
An alternate name for the zone that was specified as LINK-FROM.
Leap line fields
The format of a leap line is:
Leap YEAR MONTH DAY HH: MM: SS CORR R/ SYEAR MONTH DAY HH: MM: SS
Specify when the leap second happened.
CORR
Uses a + or a -to show whether the second was added or skipped.
R/ S

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An abbreviation of Rolling or Stationary to describe whether the leap second should be applied to local
wall clock time or to GMT.

zmore zmore [files]
Similar to more. Uncompress files and print them, one screenful at a time. Works on files compressed with
compress, gzip, or pack and with uncompressed files.

Commands
space
Print next screenful.
i[ number]
Print next screenful, or number lines. Set i to number lines.
d, ^D
Print next i, or 11, lines.
iz
Print next i lines or a screenful.
is
Skip i lines. Print next screenful.
if
Skip i screens. Print next screenful.
q, Q, :q, :Q
Go to next file, or, if current file is the last, exit zmore.
e, q
Exit zmore when the prompt "--More--( Next file: file)" is displayed.
s
Skip next file and continue.
=
Print line number.
i/ expr
Search forward for ith occurrence (in all files) of expr, which should be a regular expression. Display
occurrence, including the two previous lines of context.

in
Search forward for the ith occurrence of the last regular expression searched for.

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!command

Execute command in shell. If command is not specified, execute last shell command. To invoke a shell
without passing it a command, enter \!.

.Repeat the previous command.

znew znew [options] [files]
Uncompress .Z files and recompress them in .gz format.
Options
-9
Optimal (and slowest) compression method.
-f
Recompress even if filename. gz already exists.
-t
Test new .gz files before removing .Z files.
-v
Verbose mode.
-K
If the original .Z file is smaller than the .gz file, keep it.
-P
Pipe data to conversion program. This saves disk space.

2.8. RPC and XDR 4. Boot Methods
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Linux in a Nutshell, 3rd
Edition

Chapter 4. Boot Methods
Contents:
The Boot Process
LILO: The Linux Loader
Loadlin: Booting from MS-DOS
Dual Booting Linux and Windows NT/ 2000
Boot-time Kernel Options
initrd: Using a RAM Disk

This chapter describes some techniques for booting your Linux system. Depending on your
hardware and whether you want to run any other operating systems, you can configure the
system to boot Linux automatically or to provide a choice between several operating systems.
Choosing between operating systems is generally referred to as dual booting, but you can boot
more than two (e. g., Linux and Windows 95/ 98/ NT/ 2000). This chapter covers the following
topics:

l The boot process

l LILO: the Linux loader
l Loadlin: booting from MS-DOS
l Dual booting Linux and Windows NT/ 2000
l Boot-time kernel options
l initrd: using a RAM disk

4.1. The Boot Process
Once your Linux system is up and running, booting the system generally is pretty
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straightforward. But with the wide variety of hardware and software in use, there are many
possibilities for configuring your boot process. The three most common choices are:

l Boot Linux from a floppy, leaving any other operating system to boot from the hard
drive.

l Use the Linux Loader, LILO.[ 2] This is probably the most common method of booting
and lets you boot both Linux and other operating systems.

[2] LILO is the standard boot program for i386-architecture machines.
On the Alpha, the equivalent boot program is called MILO (Mini
Loader), and on the SPARC, it is SILO.

l Run Loadlin, which is an MS-DOS program that boots Linux from within DOS.

Other boot managers that can load Linux are available, but we don't discuss them in this
chapter. We also won't talk further about booting from a floppy except to say that whatever
method you choose for booting, you should be sure to have a working boot floppy available
for emergency use. In particular, don't experiment with the files and options in this chapter
unless you have a boot floppy, because any error could leave you unable to boot from the hard
disk.

On an Intel-based PC, the first sector of every hard disk is known as the boot sector and
contains the partition table for that disk and possibly also code for booting an operating
system. The boot sector of the first hard disk is known as the master boot record (MBR),
because when you boot the system, the BIOS transfers control to a program that lives on that
sector along with the partition table. That code is the boot loader, the code that initiates an
operating system. When you add Linux to the system, you need to modify the boot loader,
replace it, or boot from a floppy disk to start Linux.

In Linux, each disk and each partition on the disk is treated as a device. So, for example, the
entire first hard disk is known as /dev/ hda and the entire second hard disk, if there is one, is
/dev/ hdb. The first partition of the first hard drive is /dev/ hda1, and the second partition is
/dev/ hda2; the first partition of the second hard drive is /dev/ hdb1; and so on. If your drives
are SCSI instead of IDE, the naming works the same way except that the devices are /dev/ sda,
/dev/ sda1, and so on. Thus, if you want to specify that the Linux partition is the second
partition of the first hard drive (as in the examples in this chapter), you refer to it as /dev/ hda2.

The rest of the chapter describes the various techniques for booting Linux and the options that
you can specify to configure both the boot loader that you use and the Linux kernel. Both
LILO and Loadlin let you pass options to the loader and they also let you specify options for
the kernel.

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3. Linux Commands 4.2. LILO: The Linux Loader

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Linux in a Nutshell, 3rd
Edition

4.2. LILO: The Linux Loader
Once you've made the decision to install LILO, you still need to decide how it should be configured. If you want your
system to dual boot Linux and Windows 95/ 98, you can install LILO on the master boot record (MBR) and set it up to let
you select the system to boot. Dual booting Linux and Windows NT is not quite as straightforward, because Windows NT
has its own loader on the MBR, and it expects to be the one in charge. Therefore, you need to make Linux an option in the
NT loader and install LILO in the Linux partition as a secondary boot loader. The result is that the Windows NT loader
transfers control to LILO, which then boots Linux. The same applies to Windows 2000, which uses the NT loader. See
Section 4.4, "Dual Booting Linux and Windows NT/ 2000" later in this chapter for more information.

In addition to booting Linux, LILO can boot other operating systems, such as MS-DOS, Windows 95/ 98, or OS/ 2. During
installation, the major Linux distributions provide the opportunity to install LILO; it can also be installed later if necessary.
LILO can be installed on the master boot record (MBR) of your hard drive or as a secondary boot loader on the Linux
partition. LILO consists of several pieces, including the boot loader itself, a configuration file (/ etc/ lilo. conf), a map file
(/ boot/ map) containing the location of the kernel, and the lilo command (/ sbin/ lilo), which reads the configuration file and
uses the information to create or update the map file and to install the files LILO needs.

If LILO is installed on the MBR, it replaces the MS-DOS boot loader. If you have problems with your installation or you
simply want to uninstall LILO and restore the original boot loader, you can do one of the following:

l Boot Linux from a floppy disk and restore the backed-up boot sector:

% /sbin/ lilo -ul Boot to DOS and run a special version of the fdisk command that rebuilds the MBR:

C:> fdisk /mbrOne thing to remember about LILO is that it has two aspects: the boot loader and the lilo command. The lilo command
configures and installs the boot loader and updates it as necessary. The boot loader is the code that executes at system boot
time and boots Linux or another operating system.

4.2.1. The LILO Configuration File
The lilo command reads the LILO configuration file, /etc/ lilo. conf, to get the information it needs to install LILO. Among
other things, it builds a map file containing the locations of all disk sectors needed for booting.

Note that any time you change /etc/ lilo. conf or rebuild or move a kernel image, you need to rerun lilo to rebuild the map file
and update LILO.

The configuration file starts with a section of global options, described in the next section. Global options are those that
apply to every system boot, regardless of what operating system you are booting. Here is an example of a global section (a
hash sign, #, begins a comment):

boot = /dev/ hda # The boot device is /dev/ hda map = /boot/ map # Save the map file as /boot/ map install = /boot/ boot. b # The file to install as the new boot sector

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prompt # Always display the boot prompt timeout = 30 # Set a 3-second (30 tenths of a second) timeout

Following the global section, there is one section of options for each Linux kernel and for each non-Linux operating system
that you want LILO to be able to boot. Each of those sections is referred to as an image section, because each boots a
different kernel image (shorthand for a binary file containing a kernel) or another operating system. Each Linux image
section begins with an image= line.

image = /boot/ vmlinuz # Linux image file label = linux # Label that appears at the boot prompt root = /dev/ hda2 # Location of the root filesystem vga = ask # Always prompt the user for VGA mode read-only # Mount read-only to run fsck for a filesystem check

The equivalent section for a non-Linux operating system begins with other= instead of image=. For example:
other = /dev/ hda1 # Location of the partition label = dos table = /dev/ hda # Location of the partition table

Put LILO configuration options that apply to all images into the global section of /etc/ lilo. conf and options that apply to a
particular image into the section for that image. If an option is specified in both the global section and an image section, the
setting in the image section overrides the global setting for that image.

Here is an example of a complete /etc/ lilo. conf file for a system that has the Linux partition on /dev/ hda2:
## Global section boot=/ dev/ hda2 map=/ boot/ map delay= 30 timeout= 50 prompt vga= ask

## Image section: For regular Linux image=/ boot/ vmlinuz label= linux root=/ dev/ hda2 install=/ boot/ boot. b map=/ boot/ map read-only

## Image section: For testing a new Linux kernel image=/ testvmlinuz label= testlinux root=/ dev/ hda2 install=/ boot/ boot. b map=/ boot/ map read-only optional # Omit image if not available when map is built

## Image section: For booting DOS other=/ dev/ hda1 label= dos loader=/ boot/ chain. b table=/ dev/ hda # The current partition table

## Image section: For booting Windows 95 other=/ dev/ hda1

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label= win95 loader=/ boot/ chain. b table=/ dev/ hda

4.2.1.1. Global options
In addition to the options listed here, the kernel options append, read-only, read-write, root, and vga (described in
Section 4.2.1.3, "Kernel options" later) also can be set as global options.

backup= backup-file
Copies the original boot sector to backup-file instead of to the file /boot/ boot. nnnn, where nnnn is a number that
depends on the disk device type.
boot= boot-device

Sets the name of the device that contains the boot sector. boot defaults to the device currently mounted as root, such
as /dev/ hda2. Specifying a device such as /dev/ hda (without a number) indicates that LILO should be installed in the
master boot record; the alternative is to set it up on a particular partition such as /dev/ hda2.
compact

Merges read requests for adjacent disk sectors to speed up booting. Use of compact is particularly recommended
when booting from a floppy disk. Use of compact may conflict with linear.
default= name

Uses the image name as the default boot image. If default is omitted, the first image specified in the configuration
file is used.
delay= tsecs

Specifies, in tenths of a second, how long the boot loader should wait before booting the default image. If serial is
set, delay is set to 20 at a minimum. The default is to not wait.
disk= device-name

Defines parameters for the disk specified by device-name if LILO can't figure them out. Normally, LILO can
determine the disk parameters itself and this option isn't needed. When disk is specified, it is followed by one or
more parameter lines, such as:

disk=/ dev/ sda bios= 0x80 # First disk is usually 0x80, second is usually 0x81 sectors= ... heads= ...

Note that this option is not the same as the disk geometry parameters you can specify with the hd boot command-line
option. With disk, the information is given to LILO; with hd, it is passed to the kernel. The parameters that can be
specified with disk are listed briefly here. They are described in detail in the LILO User's Guide, which comes with the
LILO distribution.

bios= bios-device-code
The number the BIOS uses to refer to the device. See the previous example.
cylinders= cylinders
The number of cylinders on the disk.
heads= heads
The number of heads on the disk.

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inaccessible
Tells LILO that the BIOS can't read the disk; used to prevent the system from becoming unbootable if LILO thinks
the BIOS can read it.

partition= partition-device
Starts a new section for a partition. The section contains one variable, start= partition-offset, which specifies the
zero-based number of the first sector of the partition:

partition=/ dev/ sda1 start= 2048

sectors= sectors
The number of sectors per track.
disktab= disktab-file
This option has been superseded by the disk= option.
fix-table
If set, allows lilo to adjust 3D addresses (addresses specified as sector/ head/ cylinder) in partition tables. This is
sometimes necessary if a partition isn't track-aligned and another operating system such as MS-DOS is on the same
disk. See the lilo. conf manpage for details.

force-backup= backup-file
Like backup but overwrites an old backup copy if one exists.
ignore-table
Tells lilo to ignore corrupt partition tables.
install= boot-sector
Installs the specified file as the new boot sector. If install is omitted, the boot sector defaults to /boot/ boot. b.
lba32
Generates 32-bit Logical Block Addresses instead of sector/ head/ cylinder addresses, allowing booting from any
partition on hard disks greater than 8.4GB (i. e., it removes the 1024-cylinder limit). Requires BIOS support for the
EDD packet call interface[ 3] and at least LILO Version 21-4.

[3] If your BIOS is dated after 1998, it should include EDD packet call interface support.
linear
Generates linear sector addresses, which do not depend on disk geometry, instead of 3D (sector/ head/ cylinder)
addresses. If LILO can't determine your disk's geometry itself, you can try using linear; if that doesn't work, then
you need to specify the geometry with disk=. Note, however, that linear sometimes doesn't work with floppy disks,
and it may conflict with compact.

lock

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Tells LILO to record the boot command line and use it as the default for future boots until it is overridden by a new
boot command line. lock is useful if there is a set of options that you need to enter on the boot command line every
time you boot the system.

map= map-file
Specifies the location of the map file. Defaults to /boot/ map.
message= message-file
Specifies a file containing a message to be displayed before the boot prompt. The message can include a formfeed
character (Ctrl-L) to clear the screen. The map file must be rebuilt by rerunning the lilo command if the message file
is changed or moved. The maximum length of the file is 65,535 bytes.

nowarn
Disables warning messages.
optional
Specifies that any image that is not available when the map is created should be omitted and not offered as an option
at the boot prompt. Like the per-image option optional but applies to all images.

password= password
Specifies a password that the user is prompted to enter when trying to load an image. The password is not encrypted
in the configuration file, so if passwords are used, permissions should be set so that only the superuser is able to read
the file. This option is like the per-image version, except that all images are password-protected and they all have the
same password.

prompt
Automatically displays the boot prompt without waiting for the user to press the Shift, Alt, or Scroll Lock key. Note
that setting prompt without also setting timeout prevents unattended reboots.

restricted
Can be used with password to indicate that a password needs to be entered only if the user specifies parameters on
the command line. Like the per-image restricted option but applies to all images.

serial= parameters
Allows the boot loader to accept input from a serial line as well as from the keyboard. Sending a break on the serial
line corresponds to pressing a Shift key on the console to get the boot loader's attention. All boot images should be
password-protected if serial access is insecure (e. g., if the line is connected to a modem). Setting serial
automatically raises the value of delay to 20 (i. e., 2 seconds) if it is less than that. The parameter string parameters
has the following syntax:

port[, bps[ parity[ bits]]]For example, to initialize COM1 with the default parameters:
serial= 0,2400n8The parameters are:

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port

The port number of the serial port. The default is 0, which corresponds to COM1 (/ dev/ ttys0). The value can be one
of 0 through 3, for the four possible COM ports.

bps
The baud rate of the serial port. Possible values of bps are 110, 300, 1200, 2400, 4800, 9600, 19200, and 38400. The
default is 2400 bps.

parity
The parity used on the serial line. Parity is specified as: n or N for no parity, e or E for even parity, and o or O for
odd parity. However, the boot loader ignores input parity and strips the 8th bit.

bits
Specifies whether a character contains 7 or 8 bits. Default is 8 with no parity and 7 otherwise.
timeout= tsecs
Sets a timeout (specified in tenths of a second) for keyboard input. If no key has been pressed after the specified
time, the default image is booted automatically. timeout is also used to determine when to stop waiting for password
input. The default timeout is infinite.

verbose= level
Turns on verbose output, where higher values of level produce more output. If -v is also specified on the lilo
command line, the level is incremented by 1 for each occurrence of -v. The maximum verbosity level is 5.

4.2.1.2. Image options
The following options are specified for a particular image.
alias= name
Provides an alternate name for the image that can be used instead of the name specified with the label option.
image= pathname
Specifies the file or device containing the boot image of a bootable Linux kernel. Each per-image section that
specifies a bootable Linux kernel starts with an image option. See also the range option.

label= name
Specifies the name that is used for the image at the boot prompt. Defaults to the filename of the image file (without
the path).

loader= chain-loader
For a non-Linux operating system, specifies the chain loader to which LILO should pass control for booting that
operating system. The default is /boot/ chain. b. If the system will be booted from a drive that is neither the first hard
disk or a floppy, the chain loader must be specified.

lock

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Like lock as described in the global options section; it can also be specified in an image section.

optional
Specifies that the image should be omitted if it is not available when the map is created by the lilo command. Useful
for specifying test kernels that are not always present.

password= password
Specifies that the image is password-protected and provides the password that the user is prompted for when
booting. The password is not encrypted in the configuration file, so if passwords are used, only the superuser should
be able to read the file.

range= sectors
Used with the image option, when the image is specified as a device (e. g., image=/ dev/ fd0), to indicate the range of
sectors to be mapped into the map file. sectors can be given as the range start-end or as start+ number, where start
and end are zero-based sector numbers and number is the increment beyond start to include. If only start is
specified, only that one sector is mapped. For example:

image = /dev/ fd0 range = 1+ 512 # take 512 sectors, starting with sector 1

restricted
Specifies that a password is required for booting the image only if boot parameters are specified on the command
line.

table= device
Specifies, for a non-Linux operating system, the device that contains the partition table. If table is omitted, the boot
loader does not pass partition information to the operating system being booted. Note that /sbin/ lilo must be rerun if
the partition table is modified. This option cannot be used with unsafe.

unsafe
Can be used in the per-image section for a non-Linux operating system to indicate that the boot sector should not be
accessed when the map is created. If unsafe is specified, then some checking isn't done, but the option can be useful
for running the lilo command without having to insert a floppy disk when the boot sector is on a fixed-format floppy
disk device. This option cannot be used with table.

4.2.1.3. Kernel options
The following kernel options can be specified in /etc/ lilo. conf as well as on the boot command line:
append= string
Appends the options specified in string to the parameter line passed to the kernel. This typically is used to specify
certain hardware parameters. For example, if your system has more than 64 MB of memory (i. e., more than your
BIOS can recognize), you can use append:

append = "mem= 128M"initrd= filename
Specifies the file to load into /dev/ initrd when booting with a RAM disk. See also the options load_ ramdisk (in

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Section 4.5, "Boot-time Kernel Options"), prompt_ ramdisk, ramdisk_ size, and ramdisk_ start (in Section 4.6,
"initrd: Using a RAM Disk").
literal= string

Like append but replaces all other kernel boot options.
noinitrd

Preserves the contents of /dev/ initrd so they can be read once after the kernel is booted.
prompt_ ramdisk= n

Specifies whether the kernel should prompt you to insert the floppy disk that contains the RAM disk image, for use
during Linux installation. Values of n are:

0
Don't prompt. Usually used for an installation in which the kernel and the RAM disk image both fit on one
floppy.
1

Prompt. This is the default.
ramdisk= size

Obsolete; use only with kernels older than Version 1.3.48. For newer kernels, see the option load_ ramdisk in
Section 4.5, "Boot-time Kernel Options" as well as prompt_ ramdisk, ramdisk_ size, and ramdisk_ start, elsewhere

in this section.
ramdisk_ size= n

Specifies the amount of memory, in kilobytes, to be allocated for the RAM disk. The default is 4096, which
allocates 4 megabytes.
ramdisk_ start= offset

Used for a Linux installation in which both the kernel and the RAM disk image are on the same floppy. offset
indicates the offset on the floppy where the RAM disk image begins; it is specified in kilobytes.
root= root-device

Specifies the device that should be mounted as root. If the special name current is used as the value, the root device
is set to the device on which the root filesystem currently is mounted. Defaults to the root-device setting contained
in the kernel image.
vga= mode

Specifies the VGA text mode that should be selected when booting. mode defaults to the VGA mode setting in the
kernel image. The values are case-insensitive. They are:

ask
Prompts the user for the text mode. Pressing Enter in response to the prompt displays a list of the available
modes.
extended (or ext)

Selects 80x50 text mode.
normal

Selects normal 80x25 text mode.
number

Use the text mode that corresponds to number. A list of available modes for your video card can be obtained
by booting with vga= ask and pressing Enter.

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4.2.2. The lilo Command
You need to run the lilo command to install the LILO boot loader and to update it whenever the kernel changes or to reflect
changes to /etc/ lilo. conf.

The path to the lilo command is usually /sbin/ lilo. The syntax of the command is:
lilo [options]Some of the options correspond to /etc/ lilo. conf keywords:

Configuration Keyword Command Option
boot= bootdev -b bootdev
compact -c
delay= tsecs -d tsecs
default= label -D label
disktab= file -f file
install= bootsector -i bootsector
lba32 -L
linear -l
map= mapfile -m mapfile
fix-table -P fix
ignore-table -P ignore
backup= file -s file
force-backup= file -S file
verbose= level -v

These options should be put in the configuration file whenever possible; putting them on the lilo command line instead of
in /etc/ lilo. conf is now deprecated. The next section describes those options that can be given only on the lilo command
line; the others are described earlier in this section.

4.2.3. lilo Command Options
The following list describes those lilo command options that are available only on the command line. Multiple options are
given separately:

% lilo -q -v-C config-file
Specifies an alternative to the default configuration file (/ etc/ lilo. conf). lilo uses the configuration file to determine
what files to map when it installs LILO.

-I label

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Prints the path to the kernel specified by label to standard output or an error message if no matching label is found.
For example:

% lilo -I linux/boot/ vmlinuz-2.0.34-0.6

-q
Lists the currently mapped files. lilo maintains a file (by default /boot/ map), containing the name and location of the
kernel( s) to boot. Running lilo with this option prints the names of the files in the map file to standard output, as in
this example (in which the asterisk indicates that linux is the default):

% lilo -qlinux * test

-r root-directory
Specifies that before doing anything else, lilo should chroot to the indicated directory. Used for repairing a setup
from a boot floppy --you can boot from a floppy but have lilo use the boot files from the hard drive. For example, if
you issue the following commands, lilo will get the files it needs from the hard drive:

% mount /dev/ hda2 /mnt% lilo -r /mnt

-R command-line
Sets the default command for the boot loader the next time it executes. The command executes once and then is
removed by the boot loader. This option typically is used in reboot scripts, just before calling shutdown -r.

-t
Indicates that this is a test. Does not really write a new boot sector or map file. Can be used with -v to find out what
lilo would do during a normal run.

-u device-name
Uninstalls lilo by restoring the saved boot sector from /boot/ boot. nnnn, after validating it against a timestamp.
device-name is the name of the device on which LILO is installed, such as /dev/ hda2.

-U device-name
Like -u but does not check the timestamp.
-V
Prints the lilo version number.

4. Boot Methods 4.3. Loadlin: Booting from
MS-DOS

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Linux in a Nutshell, 3rd
Edition

4.3. Loadlin: Booting from MS-DOS
Loadlin is a Linux boot loader that you run from within a bootable MS-DOS partition; the
system must be in real DOS mode, not in an MS-DOS window running under Windows. No
installation is required; you just need to copy the executable file loadlin. exe from the Loadlin
distribution to your MS-DOS partition.[ 4] You also need a compressed Linux kernel (e. g.,

vmlinuz), which you can load from a floppy, from the DOS partition, or from a RAM disk. For
example:

[4] If Loadlin didn't come with your Linux distribution, you can download it
from any of the major Linux sites, such as the Metalab site at
http:// metalab. unc. edu/ pub/ Linux.

C:> loadlin c:\ vmlinuz root=/ dev/ hda2This example loads the Linux kernel image vmlinuz, passing it the boot parameter
root=/ dev/ hda2, telling the kernel that the Linux root partition is /dev/ hda2. (If you are using
a RAM disk, see Section 4.6, "initrd: Using a RAM Disk" later in this chapter.)

If you want to use Loadlin with Windows 95/ 98, see the Loadlin User Guide and the
Loadlin+ Win95 mini-HOWTO for how to do that. Note that if your disk uses the FAT32
filesystem, the standard techniques for using Loadlin and Windows 95 won't work; if this is
the case or if you aren't sure whether you have FAT16 or FAT32, it's important to read the
mini-HOWTO before you proceed.

Loadlin can be run directly from the DOS prompt, as in the example, or it can be invoked
from CONFIG. SYS or AUTOEXEC. BAT. Like LILO, Loadlin takes both options that direct
its operation and options (also referred to as parameters) that it passes to the kernel.

There are two forms of the Loadlin syntax:
LOADLIN @params LOADLIN [zimage_file] [options] [boot_ params]

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4.3.1. Using a Parameter File

In the first form of the preceding syntax, params is a DOS file that contains the options you
want Loadlin to run with. The Loadlin distribution comes with a sample parameter file,
test. par, that you can use as a basis for creating your own. Each line in a parameter file
contains one parameter. If you want to specify the name of the Linux kernel to use (the
image= parameter), it must be the first entry in the file. Comments start with a hash sign (#).
The entries in the parameter file can be overridden or appended on the command line. For
example, to override the value of vga set in the parameter file:

C:> LOADLIN @myparam vga= normal

4.3.2. Putting Parameters on the Command Line
In the second form of the preceding Loadlin syntax, zimage_ file is the name of a Linux kernel
to run, followed by a list of Loadlin options and/ or boot options. Specifying LOADLIN with
no parameters gives a help message listing the Loadlin options and some of the possible
kernel boot options. The message is long enough that you probably want to pipe the output
through a pager like more:

C:> LOADLIN | moreThe Loadlin options are:
-clone
Bypasses certain checks --read the LOADLIN User Guide that comes with the Loadlin
distribution before using.

-d file
Debug mode. Like -t but sends output to file as well as to standard output.
-dskreset
Causes disks to be reset after loading but before booting Linux.
-noheap
For use by serious Linux hackers only; disables use of the setup heap.
-t

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Test mode. Goes through the loading process but doesn't actually start Linux. Also sets
-v.

-txmode
Sets the screen to text mode (80x25) on startup.
-v
Verbose. Prints parameter and configuration information to standard output.
-wait= nn
After loading, waits nn (DOS) ticks before booting Linux.
In addition to these Loadlin options, the help message prints a number of kernel boot options
that you can specify. The boot options that it prints are only a few of the many available boot
options. See also the BootPrompt-HOWTO for a more complete list.

4.2. LILO: The Linux Loader 4.4. Dual Booting Linux and
Windows NT/ 2000

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4.4. Dual Booting Linux and Windows NT/ 2000
As we said earlier, when you run Windows NT, its boot loader expects to be the one in charge; therefore, the normal way to
dual boot Windows NT and Linux is to add Linux as an option on the NT boot menu. The information in this section also
applies to Windows 2000, which uses the NT loader.

To accomplish this, you need to provide the NT loader with a copy of the Linux boot sector. Here's how you do that on a
computer running Windows NT with an NTFS filesystem (note that Windows NT should be installed on your system
already). See the NT OS Loader+ Linux mini-HOWTO for more information and other alternatives.

You should have a Linux boot floppy available so that, if necessary, you can boot Linux before the NT boot loader has been
modified. You also should have a DOS-formatted floppy to transfer the boot sector to the Windows NT partition. If LILO is
already installed, you may need to modify /etc/ lilo. conf as described later. Otherwise, you'll either install LILO as part of the
Linux installation, or you can install it with the QuickInst script that comes with LILO. Once LILO is installed, and you have
a configuration file, you can set up the system for dual booting.

Note that the following instructions assume your Linux partition is on /dev/ hda2. If Linux is on another partition, be sure to
replace /dev/ hda2 in the following examples with the correct partition.

1. Specify the Linux root partition as your boot device. If you are editing /etc/ lilo. conf manually, your entry will look
like this:

boot=/ dev/ hda2and will be the same as the root= entry.
2. Run the lilo command to install LILO on the Linux root partition.
3. At this point, if you need to reboot Linux, you'll have to use the boot floppy, because the NT loader hasn't been set up
yet to boot Linux.

4. From Linux, run the dd command to make a copy of the Linux boot sector:
% dd if=/ dev/ hda2 of=/ bootsect. lnx bs= 512 count= 1This command copies one block, with a blocksize of 512 bytes, from the input file /dev/ hda2 to the output file
/bootsect. lnx. (The output filename can be whatever makes sense to you; it doesn't have to be bootsect. lnx.)

5. Copy bootsect. lnx to a DOS-formatted floppy disk:
% mount -t msdos /dev/ fd0 /mnt% cp /bootsect. lnx /mnt% umount /mnt

6. Reboot the system to Windows NT and copy the boot sector from the floppy disk to the hard disk. For example, using
the command line to copy the file:

C:> copy a:\ bootsect. lnx c:\ bootsect. lnx

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It doesn't matter where on the hard drive you put the file because you'll tell the NT loader where to find it in step 8.
7. Modify the attributes of the file boot. ini[ 5] to remove the system and read-only attributes so you can edit it:

[5] boot. ini is the Windows NT counterpart to /etc/ lilo. conf. It defines what operating systems the NT
loader can boot.

C:> attrib -s -r c:\ boot. ini8. Edit boot. ini with a text editor to add the line:
C:\ bootsect. lnx=" Linux"This line adds Linux to the boot menu and tells the Windows NT boot loader where to find the Linux boot sector.
You can insert the line anywhere in the [operating systems] section of the file. Its position in the file determines
where it will show up on the boot menu when you reboot your computer. Adding it at the end, for example, results in
a boot. ini file that looks something like this (the second multi( 0) entry is wrapped to fit in the margins of this page):

[boot loader] timeout= 30 default= multi( 0) disk( 0) rdisk( 0) partition( 1)\ WINNT [operating systems] multi( 0) disk( 0) rdisk( 0) partition( 1)\ WINNT=" Windows NT Server Version 4.00" multi( 0) disk( 0) rdisk( 0) partition( 1)\ WINNT=" Windows NT Server Version 4.00 [VGA mode]" /basevideo /sos C:\ bootsect. lnx=" Linux"

If you want Linux to be the default operating system, modify the default= line to say:
default= C:\ bootsect. lnx9. Rerun attrib to restore the system and read-only attributes:
C:> attrib +s +r c:\ boot. iniNow you can shut down Windows NT and reboot; NT will prompt you with a menu that looks something like this:
OS Loader V4.00 Please select the operating system to start: Windows NT Workstation Version 4.00 Windows NT Workstation Version 4.00 [VGA mode] Linux

Select Linux, and the NT loader reads the Linux boot sector and transfers control to LILO, on the Linux partition.
If you later modify /etc/ lilo. conf or rebuild the kernel, you need to rerun the lilo command, create a new bootsect. lnx file, and
replace the version of bootsect. lnx on the Windows NT partition with the new version. That is, you need to rerun steps 2-6.

NOTE
If you have any problems or you simply want to remove LILO later, you can reverse the installation
procedure: boot to Windows NT, change the system and read-only attributes on boot. ini, reedit boot. ini to
remove the Linux entry, save the file, restore the system and read-only attributes, and remove the Linux boot
sector from the NT partition.

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4.3. Loadlin: Booting from
MS-DOS
4.5. Boot-time Kernel
Options

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Linux in a Nutshell, 3rd
Edition

4.5. Boot-time Kernel Options
The Loadlin and LILO sections of this chapter described some of the options you can specify
when you boot Linux. There are many more options that can be specified. This section
touches on the ways to pass options to the kernel and then describes some of the kinds of
parameters you might want to use. The parameters in this section affect the kernel and
therefore apply regardless of which boot loader you use.

As always with Unix systems, there are a number of choices for the boot process itself. If you
are using Loadlin, you can pass parameters to the kernel on the command line or in a file.

If LILO is your boot loader, you can add to or override the parameters specified in
/etc/ lilo. conf during the boot process as follows:

l If prompt is set in /etc/ lilo. conf, LILO always presents the boot prompt and waits for
input. At the prompt, you can choose the operating system to be booted. If you choose
Linux, you also can specify parameters.

l If prompt isn't set, when the word "LILO" appears, press Control, Shift, or Alt, and
the boot prompt appears. You also can press the Scroll Lock key before LILO is
printed and not have to wait poised over the keyboard for the right moment.

l At the boot prompt, specify the system you want to boot or press Tab to get a list of the
available choices. You then can enter the name of the image to boot. For example:

LILO boot: <press Tab> linux test dos boot:linux

You also can add boot command options:
boot: linux singlel If you don't provide any input, LILO waits the amount of time specified in the delay
parameter and then boots the default operating system with the default parameters as

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set in /etc/ lilo. conf.

Some of the boot parameters have been mentioned earlier. Many of the others are hardware-specific
and are too numerous to mention here. For a complete list of parameters and a
discussion of the booting process, see the BootPrompt-HOWTO. Some of the parameters not
shown earlier that you might find useful are listed next; many more are covered in the
HOWTO. Most of the following parameters are used to provide information or instructions
for the kernel, rather than to LILO.

debug
Prints all kernel messages to the console.
hd= cylinders, heads, sectors
Specifies the hard drive geometry to the kernel. Useful if Linux has trouble
recognizing the geometry of your drive, especially if it's an IDE drive with more than
1024 cylinders.

load_ ramdisk= n
Tells the kernel whether to load a RAM disk image for use during Linux installation.
Values of n are:

0
Don't try to load the image. This is the default.
1
Load the image from a floppy disk to the RAM disk.
mem= size
Specifies the amount of system memory installed. Useful if your BIOS reports memory
only up to 64 MB and your system has more memory installed. Specify as a number
with M or k (case-insensitive) appended:

mem= 128MBecause mem would have to be included on the command line for every boot, it often is
specified on a command line saved with lock or with append to be added to the parameters
passed to the kernel.

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noinitrd

When set, disables the two-stage boot and preserves the contents of /dev/ initrd so the
data is available after the kernel has booted. /dev/ initrd can be read only once, and then
its contents are returned to the system.

number
Starts Linux at the runlevel specified by number. A runlevel is an operating state that
the system can be booted to, such as a multiuser system or a system configuration
running the X Window System. A runlevel is generally one of the numbers from 1 to
6; the default usually is 3. The runlevels and their corresponding states are defined in
the file /etc/ inittab. See the manpage for /etc/ inittab for more information.

ro
Mounts the root filesystem read-only. Used for doing system maintenance, such as
checking the filesystem integrity, when you don't want anything written to the
filesystem.

rw
Mounts the root filesystem read-write. If neither ro nor rw is specified, the default
value (usually rw) stored in the kernel image is used.

single
Starts Linux in single-user mode. This option is used for system administration and
recovery. It gives you a root prompt as soon as the system boots, with minimal
initialization. No other logins are allowed.

4.4. Dual Booting Linux and
Windows NT/ 2000
4.6. initrd: Using a RAM
Disk

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4.6. initrd: Using a RAM Disk
Modern Linux distributions use a modular kernel, which allows modules to be added without requiring that the kernel be
rebuilt. If your root filesystem is on a device whose driver is a module, as is frequently true of SCSI disks, you can use the
initrd facility, which provides a two-stage boot process, to first set up a temporary root filesystem in a RAM disk containing
the modules you need to add (e. g., the SCSI driver) and then load the modules and mount the real root filesystem. The RAM
disk containing the temporary filesystem is the special device file /dev/ initrd.

Before you can use initrd, both RAM disk support (CONFIG_ BLK_ DEV_ RAM= y) and initial RAM disk support
(CONFIG_ BLK_ DEV_ INITRD= y) must be compiled into the Linux kernel. Then you need to prepare the normal root
filesystem and create the RAM disk image. Your Linux distribution may have utilities to do some of the setup for you; for
example, the Red Hat distribution comes with the mkinitrd command, which builds the initrd image. For detailed
information, see the initrd manpage and the file initrd. txt (the path may vary but is usually something like
/usr/ src/ linux/ Documentation/ initrd. txt).

Once your Linux system has been set up for initrd, you can do one of the following, depending on which boot loader you
are using:

l If LILO is your boot loader, add the initrd option to the appropriate image section:

image = /vmlinuz initrd = /boot/ initrd # The file to load as the contents of /dev/ initrd ...

Run the /sbin/ lilo command, and you can reboot with initrd.
l If you are using Loadlin, add the initrd option to the command line:

loadlin c:\ linux\ vmlinuz initrd= c:\ linux\ initrd

4.5. Boot-time Kernel
Options
5. Red Hat and Debian
Package Managers

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Linux in a Nutshell, 3rd
Edition

Chapter 5. Red Hat and Debian Package
Managers
Contents:
The Red Hat Package Manager
The Debian Package Manager

This chapter describes the two major Linux packaging systems, the Red Hat Package Manager (RPM) and the
Debian GNU/ Linux Package Manager.

When you want to install applications on your Linux system, most often you'll find a binary or a source package
containing the application you want, instead of (or in addition to) a .tar. gz file. A package is a file containing the
files necessary to install an application. But note that while the package contains the files you need for installation,
the application might require the presence of other files or packages that are not included, such as particular
libraries (and even specific versions of the libraries), in order to be able to run. Such requirements are known as
dependencies.

Package management systems offer many benefits. As a user, you may find you want to query the package
database to find out what packages are installed on the system and their versions. As a system administrator, you
need tools to install and manage the packages on your system. And, if you are also a developer, you need to know
how to build a package for distribution.

Among other things, package managers:
l Provide tools for installing, updating, removing, and managing the software on your system.

l Let you install new or upgraded software directly across a network.
l Tell you what software package a particular file belongs to or what files a package contains.
l Maintain a database of packages on the system and their state, so you can find out what packages or
versions are installed on your system.

l Provide dependency checking, so you don't mess up your system with incompatible software.

l Provide PGP, MD5, or other signature verification tools.
l Provide tools for building packages.

Any user can list or query packages. However, installing, upgrading, or removing packages generally requires
superuser privileges. This is because the packages normally are installed in systemwide directories that are

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writable only by root. Sometimes you can specify an alternate directory, to install, for example, a package into
your home directory or into a project directory where you have write permission.

Both RPM and the Debian Package Manager back up old files before installing an updated package. Not only does
this let you go back if there is a problem, but also if you've made changes (to configuration files, for example),
they aren't completely lost.

5.1. The Red Hat Package Manager
The Red Hat Package Manager (RPM) is a freely available packaging system for software distribution and
installation. In addition to Red Hat and Red Hat-based distributions, both SuSE and Caldera are among the Linux
distributions that use RPM.

Using RPM is straightforward. A single command, rpm, has options to perform all the package functions. For
example, to find out if the Emacs editor is installed on your system, you could say:

% rpm -q emacsemacs-20.4-4

In addition, the GNOME-RPM program provides an X-based graphical frontend to RPM (that can be run even if
you are not running GNOME). This section describes the rpm command and then the gnorpm command that runs
GNOME-RPM.

5.1.1. The rpm Command
RPM packages are built, installed, and queried with the rpm command. RPM package names usually end with a
.rpm extension. rpm has a set of modes, each with its own options. The format of the rpm command is:

rpm [options] [packages]With a few exceptions, as noted in the lists of options that follow, the first option specifies the rpm mode (e. g.,
install, query, update, build, etc.), and any remaining options affect that mode.

In the option descriptions that refer to packages, you'll sometimes see them specified as package-name and
sometimes as package-file. The package name is the name of the program or application, such as gif2png. The
package file is the name of the RPM file: gif2png-2.2.5-1. i386. rpm.

RPM provides a configuration file for specifying frequently used options. The system configuration file is usually
/etc/ rpmrc, and users can set up their own $HOME/. rpmrc file. You can use the --showrc option to show the
values RPM will use for all the options that may be set in an rpmrc file:

rpm --showrcThe rpm command includes FTP and HTTP clients, so you can specify an ftp:// or http:// URL to install or query
a package across the Internet. You can use an FTP or HTTP URL wherever package-file is specified in the
commands presented here.

Any user can query the RPM database. Most of the other functions require superuser privileges.

5.1.1.1. General options
The following options can be used with all modes:
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--dbpath path
Use path as the path to the RPM database.
--ftpport port
Use port as the FTP port.
--ftpproxy host
Use host as a proxy server for all transfers. Specified if you are FTPing through a firewall system that uses
a proxy.

--help
Print a long usage message (running rpm with no options gives a shorter usage message).
--justdb
Update only the database; don't change any files.
--pipe command
Pipe the rpm output to command.
--quiet
Display only error messages.
--rcfile filename
Use filename as the configuration file instead of the system configuration file /etc/ rpmrc or
$HOME/. rpmrc.

--root dir
Perform all operations within directory dir.
--version
Print the version number of rpm.
-vv
Print debugging information.

5.1.1.2. Install, upgrade, and freshen options
Install or upgrade an RPM package. The syntax of the install command is:
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rpm --install [install-options] package_ file ...

To install a new version of a package and remove an existing version at the same time, use the upgrade command
instead:

rpm -U [install-options] package_ file ...rpm --upgrade [install-options] package_ file ...

One feature of -U is that if the package doesn't already exist on the system, it acts like -i and installs it. To prevent
that behavior, you can freshen a package instead; in that case, rpm upgrades the package only if an earlier version
is already installed. The freshen syntax is:

rpm -F [install-options] package_ file ...rpm --freshen [install-options] package_ file ...

Installation and upgrade options are:
--allfiles
Install or upgrade all files.
--badreloc
Used with --relocate to force relocation even if the package is not relocatable.
--excludedocs
Don't install any documentation files.
--excludepath path
Don't install any file whose filename begins with path.
--force
Force the installation. Equivalent to using --replacepkgs, --replacefiles, and --oldpackage.
-h, --hash
Print 50 hash marks as the package archive is unpacked. Use with --version for a nicer display.
--ignorearch
Install even if the binary package is intended for a different architecture.
--ignoreos
Install binary package even if the operating systems don't match.
--ignoresize
Don't check disk space availability before installing.

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--includedocs
Install documentation files. This is needed only if excludedocs: 1 is specified in an rpmrc file.
--nodeps
Don't check whether this package depends on the presence of other packages.
--noorder
Don't reorder packages to satisfy dependencies before installing.
--noscripts
Don't execute any preinstall or postinstall scripts.
--notriggers
Don't execute any scripts triggered by package installation.
--oldpackage
Allow an upgrade to replace a newer package with an older one.
--percent
Print percent-completion messages as files are unpacked.
--prefix path
Set the installation prefix to path for relocatable packages.
--replacefiles
Install the packages even if they replace files from other installed packages.
--replacepkgs
Install the packages even if some of them are already installed.
--test
Go through the installation to see what it would do, but don't actually install the package.

5.1.1.3. Query options
The syntax for the query command is:
rpm -q[ information-options] [package-options]rpm --query[ information-options] [package-options]

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There are two subsets of query options: package selection options that determine what packages to query and
information selection options that determine what information to provide.

5.1.1.3.1. Package selection options
package_ name
Query the installed package package_ name.
-a, --all
Query all installed packages.
-f file, --file file
Find out what package owns file.
-g group, --group group
Find out what packages have group group.
-p package_ file
Query the uninstalled package package_ file.
--querybynumber num
Query the numth database entry. Primarily useful for debugging.
-qf, --queryformat num
Specify the format for displaying the query output, using tags to represent different types of data (e. g.,
NAME, FILENAME, DISTRIBUTION). The format specification is a variation of the standard printf
formatting. (Use --querytags in Section 5.1.1.8, "Miscellaneous options" to view a list of available tags.

--specfile specfile

Query specfile as if it were a package.
--triggeredby pkg

List packages that trigger installation of package pkg.
--whatrequires capability

List packages that require the given capability to function.
--whatprovides capability

List packages that provide the given capability.
5.1.1.3.2. Information selection options
-c, --configfiles
List configuration files in the package.

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--changelog
Display the log of change information for the package.
-d, --docfiles
List documentation files in the package.
--dump
Dump information for each file in the package. This option must be used with at least one of -l, -c, or -d.
The output includes the following information in this order:

path size mtime md5sum mode owner group isconfig isdoc rdev symlink--filesbypkg
List all files in each package.
-i
Display package information, including the name, version, and description.
-l, --list
List all files in the package.
--last
List packages by install time, with the latest packages listed first.
--provides
List the capabilities this package provides.
-R, --requires
List any packages this package depends on.
-s, --state
List each file in the package and its state. The possible states are normal, not installed, or replaced.
--scripts
List any package-specific shell scripts used during installation and uninstallation of the package.

5.1.1.4. Uninstall options
The syntax for the uninstall command is:

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rpm -e package_ namerpm --erase package_ name

The uninstall options are:
--allmatches
Remove all versions of the package. Only one package should be specified; otherwise, an error results.
--nodeps
Don't check dependencies before uninstalling the package.
--noscripts
Don't execute any preuninstall or postuninstall scripts.
--notriggers
Don't execute any scripts triggered by the removal of this package.
--test
Don't really uninstall anything; just go through the motions.

5.1.1.5. Verify options
The syntax for the verify command is:
rpm -V|-y| --verify[ package-selection-options]Verify mode compares information about the installed files in a package with information about the files that
came in the original package and displays any discrepancies. The information compared includes the size, MD5
sum, permissions, type, owner, and group of each file. Uninstalled files are ignored.

The package selection options include those available for query mode, as well as the following:
--nofiles
Ignore missing files.
--nomd5
Ignore MD5 checksum errors.
--nopgp
Ignore PGP checking errors.
The output is formatted as an eight-character string, possibly followed by a "c" to indicate a configuration file, and
then the filename. Each of the eight characters in the string represents the result of comparing one file attribute to
the value of that attribute from the RPM database. A period (.) indicates that the file passed that test. The

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following characters indicate failure of the corresponding test:

5 MD5 sum
D Device
G Group
L Symlink
M Mode (includes permissions and file type)
S File size
T Mtime
U User

5.1.1.6. Database rebuild options
The syntax of the command to rebuild the RPM database is:
rpm --rebuilddb [options]You also can build a new database:
rpm --initdb [options]The options available with the database rebuild mode are the --dbpath and --root options described earlier under
Section 5.1.1.1, "General options".

5.1.1.7. Signature check options
RPM packages may have a PGP signature built into them. PGP configuration information is read from /etc/ rpmrc.
The syntax of the signature-check mode is:

rpm --checksig package_ file...rpm -K package_ file...

The signature-checking options are:
--nogpg
Don't check any GPG signatures.
--nomd5
Don't check any MD5 signatures.
--nopgp
Don't check any PGP signatures.

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Two other options let you add signatures to packages:

--addsign binary-pkgfile...
Generate and append new signatures to those that already exist in the specified binary packages.
--resign binary-pkgfile...
Generate and insert new signatures in the specified binary packages, removing any existing signatures.

5.1.1.8. Miscellaneous options
Several additional rpm options are available:
--querytags
Print the tags available for use with the --queryformat option in query mode.
--setgids packages
Set file owner and group of the specified packages to those in the database.
--setperms packages
Set file permissions of the specified packages to those in the database.
--showrc
Show the values rpm will use for all options that can be set in an .rpmrc file.

5.1.1.9. FTP/ HTTP options
The following options are available for use with ftp:// and http:// URLs in install, update, and query modes:
--ftpport port
Use port for making an FTP connection on the proxy FTP server instead of the default port. Same as
specifying the macro _ftpport.

--ftpproxy host
Use host as the proxy server for FTP transfers through a firewall that uses a proxy. Same as specifying the
macro _ftpproxy.

--httpport port
Use port for making an HTTP connection on the proxy HTTP server instead of the default port. Same as
specifying the macro _httpport.

--httpproxy host

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Use host as a proxy server for HTTP transfers. Same as specifying the macro _httpproxy.

5.1.1.10. Build options
The syntax for the build options is:
rpm -[ b| t] step [build-options] spec-file ...Specify -b to build a package directly from a spec file or -t to open a tarred gzipped file and use its spec file. Both
forms take the following single-character step arguments:

p
Perform the prep stage, unpacking source files and applying patches.
l
Do a list check, expanding macros in the files section of the spec file and verifying that each file exists.
c
Perform the build stage. Done after the prep stage; generally equivalent to doing a make.
i
Perform the install stage. Done after the prep and build stages; generally equivalent to doing a make
install.

b
Build a binary package. Done after prep, build, and install.
s
Build a source package. Done after prep, build, and install.
a
Build both binary and source packages. Done after prep, build, and install.
The following additional options can be used when building an rpm file:
--buildarch arch
--buildos os

For use with pre-3.0 versions of RPM. Build the package for architecture arch or the operating system os.
Replaced in 3.0 with --target.

--buildroot dir
Override the BuildRoot tag with dir when building the package.

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--clean

Clean up (remove) the build files after the package has been made.
--rmsource
Remove the source files and the spec file when the build is done. Can be used as a standalone option with
rpm to clean up files separately from creating the packages.

--short-circuit
Can be used with -bc and -bi to skip previous stages.
--sign
Add a PGP signature to the package.
--target platform
When building the package, set the macros _target, _target_ arch, and _target_ os to the value indicated
by platform.

--test
Go through the motions, but don't execute any build stages. Used for testing spec files.
--timecheck
Set the timecheck age (the maximum age in seconds of a file being packaged). Set to 0 to disable.
Two other options can be used standalone with rpm to recompile or rebuild a package:
--rebuild source-pkgfile...
Like --recompile, but also build a new binary package. Remove the build directory, the source files, and
the spec file once the build is complete.

--recompile source-pkgfile...
Install the named source package, and prep, compile, and install the package.

5.1.1.11. RPM examples
Query the RPM database to find Emacs-related packages:
% rpm -q -a | grep emacsQuery an uninstalled package, printing information about the package, and list the files it contains:
% rpm -qpil ~/ downloads/ bash2-doc-2.03-8. i386. rpmInstall a package (assumes superuser privileges):

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% rpm -i sudo-1.5.3-6. i386. rpm5.1.2. GNOME-RPM
GNOME-RPM is a graphical user frontend to rpm that runs under X. You can run gnorpm even if you are not
running GNOME. When you run gnorpm, it opens a window that lets you manage your rpm packages via a
graphical interface. The format of the gnorpm command is:

gnorpm [options]

5.1.2.1. gnorpm options
The gnorpm options are:
--geometry= geom
Specify the geometry of the main window in standard X geometry format (i. e., w� h+ x+ y).
-i pkgfiles, --install pkgfiles
Install the specified packages.
-p pkgs, --packages pkgs
The packages are in files, not in the rpm database (i. e., they haven't been installed yet).
-q pkgs, --query pkgs
Display a query window for the specified installed packages.
-qp pkgfiles, --query --packages pkgfiles
Display a query window for the specified package files. This is the same as specifying the -q and -p
options.

-U pkgfiles, --upgrade pkgfiles
Upgrade the specified packages.
-K pkgfiles, --checksig pkgfiles
Check the signatures on the specified packages.
-y pkgs, --verify pkgs
Verify the specified packages.
-?, --help
Display a help message and exit.

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--root= dir

Specify the filesystem root to use.
--usage
Display a brief usage message and exit.

5.1.2.2. The GNOME-RPM window
The GNOME-RPM main window has five parts. At the top is a menu bar with three buttons:
Packages
Menu options are Query, Uninstall, and Verify.
Operations
Menu options are Find, Web find, Install, and Preferences.
Help
Provides online help for GNOME-RPM.
Below the menu bar is a toolbar, with buttons to Install, Unselect, Uninstall, Query, Verify, Find, and Web find.
At the very bottom of the window is a status bar.

The rest of the window is the main panel. On the left is the package panel, which displays package folders in a
tree structure. Clicking on a folder selects it; double-click to display the contents of the folder (i. e., the packages in
that folder) on the righthand panel. Clicking on a package selects it; you then can use the menus and the toolbar
buttons to operate on the package. You can select several packages at the same time and operate on them as a
group. Right-clicking on a package icon selects the package if it isn't already and presents a menu with Query,
Uninstall, and Verify options.

See the GNOME-RPM documentation and online help for full details.

4.6. initrd: Using a RAM
Disk
5.2. The Debian Package
Manager

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Linux in a Nutshell, 3rd
Edition

5.2. The Debian Package Manager
Debian GNU/ Linux provides several package management tools, primarily intended to facilitate the building, installation,
and management of binary packages. Debian package names generally end in .deb. The Debian package management tools
include:

dpkg
Until recently, the most important of the Debian packaging tools and still the primary package management program.
Used to install or uninstall packages or as a frontend to dpkg-deb.

dpkg-deb
Lower-level packaging tool. Used to create and manage the Debian package archives. Accepts and executes
commands from dpkg or can be called directly.

dselect
An interactive frontend to dpkg.
apt-get
The currently available piece of the Advanced Package Tool (APT), which is still being developed and is intended to
be a modern, user-friendly package management tool. Can be run from the command line or selected as a method
from dselect. One of the features of apt-get is that you can use it to get and install packages across the Internet by
specifying an ftp:// or http:// URL. Another feature is that you can use it to upgrade all packages currently installed on
your system in a single operation.

5.2.1. Files
Some important files used by the Debian package management tools are:
control
Comes with each package; documents dependencies; contains the name and version of the package, a description,
maintainer, installed size, and so on.

conffiles
Comes with each package and contains a list of the configuration files associated with the package.
preinst, postinst, prerm, postrm
Scripts that can be included in a package to be run before installation, after installation, before removal, or after
removal of the package.

/var/ lib/ dpkg/ available

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Contains information about packages available on the system.

/var/ lib/ dpkg/ status
Contains information about the status of packages available on the system.
/etc/ apt/ sources. list
A list for APT of package sources, used to locate packages. The sources are listed one per line, in order of preference.
/etc/ apt/ apt. conf
The main APT configuration file.

5.2.2. Package States and Selection States
The possible states that a package can be in are:
config-files
Only the configuration files for the package are present on the system.
half-configured
The package is unpacked and configuration was started but not completed.
half-installed
Installation was started but not completed.
installed
The package is unpacked and configured.
not-installed
The package is not installed.
unpacked
The package is unpacked but not configured.
The possible package selection states are:
deinstall
The package has been selected for deinstallation (i. e., for removal of everything but configuration files).
install
The package has been selected for installation.
purge
The package has been selected to be purged (i. e., for removal of everything including the configuration files).

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5.2.3. Package Flags

There are two possible package flags that can be set for a package. They are:
hold
The package is not to be handled by dpkg, unless forced with the --force-hold option.
reinst-required
The package is broken and needs to be reinstalled. Such a package cannot be removed, unless forced with the --force-reinstreq
option.

5.2.4. Scripts
In addition to the commands described in the next subsection, several shell and Perl scripts are included with the package
manager for use in building packages:

dpkg-buildpackage
Help automate package building. Shell script.
dpkg-distaddfile
Add an entry for a file to debian/ files. Perl script.
dpkg-genchanges
Generate an upload control file from the information in an unpacked, built, source tree and the files it has generated.
Perl script.

dpkg-gencontrol
Read information from an unpacked source tree and display a binary package control file on standard output. Perl
script.

dpkg-name
Rename Debian packages to their full package names. Shell script.
dpkg-parsechangelog
Read and parse the changelog from an unpacked source tree and write the information to standard output in machine-readable
form. Perl script.

dpkg-scanpackages
Create a Packages file from a tree of binary packages. The Packages file is used by dselect to provide a list of
packages available for installation. Perl script.

dpkg-shlibdeps
Calculate shared library dependencies for named executables. Perl script.
dpkg-source

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Pack and unpack Debian source archives. Perl script.

5.2.5. Debian Package Manager Command Summary

apt-cdrom apt-cdrom [options] command
Add a new CD-ROM to APT's list of available sources. Currently, the only command is add, which is required
(except with the --help option). The database of CD-ROM IDs that APT maintains is /var/ state/ apt/ cdroms. list.

Options
Options can be specified on the command line or they may be set in the configuration file. Boolean options set in
the configuration file can be overridden on the command line in a number of different ways, a couple of which
are --no-opt and -opt= no, where opt is the single-character or full name of the option.

-a, --thorough
Do a thorough package scan. May be needed with some old Debian CD-ROMs.
-c, --config-file
Specify a configuration file to be read after the default configuration file.
-d, --cdrom
Specify the CD-ROM mount point, which must be listed in /etc/ fstab. The configuration option is
Acquire:: cdrom:: mount.

-f, --fast
Do a fast copy, assuming the files are valid and don't all need checking. Specify this only if this disk has
been run before without error. The configuration option is APT:: CDROM:: Fast.

-h, --help
Print help message and exit.
-m, --no-mount
Don't mount or unmount the mount point. The configuration option is APT:: CDROM:: NoMount.
-n, --just-print, --recon, --no-act
Check everything, but don't actually make any changes. The configuration option is
APT:: CDROM:: NoAct.

-o, --option
Set a configuration option. Syntax is -o group:: tool= option (e. g., APT:: CDROM= Fast).
-r, --rename
Prompt for a new label and rename the disk to the new value. The configuration option is
APT:: CDROM:: Rename.

-v, --version

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Print the version information and exit.

apt-get apt-get [options] command [package...]
A command-line tool for handling packages. Will eventually be a backend to APT.
Commands
autoclean
Like clean, but remove only package files that can no longer be downloaded.
clean
Clear the local repository of retrieved package files.
check
Update the package cache and check for broken packages.
dist-upgrade
Like upgrade but also handle dependencies intelligently.
dselect-upgrade
Used together with dselect. Track the changes made by dselect to the Status field of available packages
and take actions necessary to realize that status.

install package...
Install one or more packages. Specify the package name, not the full filename. Other required packages
also are retrieved and installed. With a hyphen appended to the package name, the package is removed if
it is already installed.

remove package...
Remove one or more packages. Specify the package name, not the full filename. With a plus sign
appended to the name, the package is installed.

source package...
Find source packages and download them into the current directory. If specified with --compile, the
source packages are compiled into binary packages. With --download-only, the source packages are not
unpacked.

update
Resynchronize the package overview files from their sources. Must be done before an upgrade or dist-upgrade.

upgrade
Install the latest versions of all packages currently installed. Run update first.
Options
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Options can be specified on the command line or they may be set in the configuration file. Boolean options set in
the configuration file can be overridden on the command line in one of several ways, a couple of which are --no-opt
and -opt= no, where opt is the single-character or full name of the option.

-b, --compile, --build
Compile source packages after download.
-c, --config-file
Specify a configuration file to read after the default.
-d, --download-only
Retrieve package files, but don't unpack or install them. The configuration option is APT:: Get:: Download-only.

-f, --fix-broken
Try to fix a system with broken dependencies. Can be used alone or with a command. The configuration
option is APT:: Get:: Fix-Broken.

--force-yes
Force yes. Causes APT to continue without prompting if it is doing something that could damage your
system. Use with great caution and only if absolutely necessary. The configuration option is
APT:: Get:: force-yes.

-h, --help
Display a help message and exit.
--ignore-hold
Ignore a hold placed on a package. Use with dist-upgrade to override many undesired holds. The
configuration option is APT:: Get:: Ignore-Hold.

-m, --ignore-missing, --fix-missing
Ignore missing or corrupted packages or packages that cannot be retrieved. Can cause problems when
used with -f.

--no-download
Disable package downloading; use with --ignore-missing to force APT to use only the packages that
have already been downloaded.

--no-upgrade
Do not upgrade packages. Use with install to prevent upgrade of packages that are already installed. The
configuration option is APT:: Get:: no-upgrade.

-o, --option
Set a configuration option. Syntax is -o group:: tool= option (e. g., APT:: Get= force-yes).

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--print-uris

Print URIs of files instead of fetching them. Print path, destination filename, size, and expected MD5
hash. The configuration option is APT:: Get:: Print-URIs.

-q, --quiet
Quiet. Omit progress indicators, produce only logging output. Add a q to make even quieter.
-s, --simulate, --just-print, --dry-run, --recon, --no-act
Go through the motions, but don't actually make any changes to the system. The configuration option is
APT:: Get:: Simulate.

-u, --show-upgraded
Print a list of all packages to be upgraded. The configuration option is APT:: Get:: Show-Upgraded.
-v, --version
Display the version and exit.
-y, --yes, --assume-yes
Automatically reply "yes" to prompts and run noninteractively. Abort if there is an error. The
configuration option is APT:: Get:: Assume-Yes.

dpkg dpkg [options] action
A tool for installing, managing, and building packages. Serves as a frontend to dpkg-deb.
dpkg actions
These actions are carried out by dpkg itself:
-i pkgfile, --install pkgfile
Install the package specified as pkgfile. With -R or --recursive, pkgfile must be a directory.
--unpack pkgfile
Unpack the package, but don't configure it. With -R or --recursive, pkgfile must be a directory.
--configure [packages|-a|--pending]
Reconfigure one or more unpacked packages. If -a or --pending is given instead of packages, configure
all packages that are unpacked but not configured.

-r, --remove [packages|-a|--pending]
--purge [packages|-a|--pending]

Remove or purge one or more installed packages. Removal gets rid of everything except the
configuration files listed in debian/ conffiles; purging also removes the configuration files. If -a or --
pending is given instead of packages, dpkg removes or purges all packages that are unpacked and
marked (in /var/ lib/ dpkg/ status) for removing or purging.

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--print-avail package

Print the details about package from /var/ lib/ dpkg/ available.
--update-avail pkgs-file
--merge-avail pkgs-file

Update the record of available files kept in /var/ lib/ dpkg/ available. This information is used by dpkg and
dselect to determine what packages are available. Update will replace the information with the contents
of the pkgs-file, distributed as Packages. Merge combines the information from Packages with the
existing information.

-A pkgfile, --record-avail pkgfile
Update the record of available files kept in /var/ lib/ dpkg/ available with information from pkgfile. This
information is used by dpkg and dselect to determine what packages are available. With -R or --
recursive, pkgfile must be a directory.

--forget-old-unavail
Forget about uninstalled unavailable packages.
--clear-avail
Remove existing information about what packages are available.
-l, --list [pkg-name-pattern]
List all packages whose names match the specified pattern. With no pattern, list all packages in
/var/ lib/ dpkg/ available. The pattern can include standard shell wildcard characters and may have to be
quoted to prevent the shell from doing filename expansion.

-s packages, --status packages
Report the status of one or more packages by displaying the entry in the status database
/var/ lib/ dpkg/ status.

-C, --audit
Search for partially installed packages and suggest how to get them working.
--get-selections [pattern]
Get list of package selections and write to standard output. With pattern specified, write selections that
match the pattern.

--set-selections
Set package selections based on input file read from standard input.
--yet-to-unpack
Search for uninstalled packages that have been selected for installation.
-L packages, --listfiles packages
List installed files that came from the specified package or packages.

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-S filename-pattern, --search filename-pattern
Search installed packages for a filename. The pattern can include standard shell wildcard characters and
may have to be quoted to prevent the shell from doing filename expansion.

--print-architecture
Print target architecture.
--print-gnu-build-architecture
Print the GNU version of the target architecture.
--print-installation-architecture
Print host architecture for installation.
--compare-versions ver1 op ver2
Perform a binary comparison of two version numbers. The operators lt le eq ne ge gt treat a
missing version as earlier. The operators lt-nl le-nl ge-nl gt-nl treat a missing version as
later (where nl is "not later"). There is a third set of operators (< << <= = >= >> >) that is
provided for compatibility with control-file syntax. dpkg returns zero for success (i. e., the condition is
satisfied) and nonzero otherwise.

--help
Print help message and exit.
--force-help
Print help message about the --force-list options and exit.
-Dh, --debug= help
Print debugging help message and exit.
--license
Print dpkg license information and exit. Accepts the spelling --licence in addition to --license.
--version
Print dpkg version information and exit.
dpkg-deb actions
The following actions can be specified for dpkg and are passed to dpkg-deb for execution. Also see dpkg-deb.
-b dir [archive], --build dir [archive]
Build a package.
-c archive, --contents archive
List the contents of a package.

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-e, --control archive dir
Extract control information from a package.
-f archive [control-fields], --field archive [control-fields]
Display the control field or fields of a package.
-I archive [control-files], --info archive [control-files]
Show information about a package.
--fsys-tarfile archive
Display the filesystem tar-file contained by a package.
-x archive dir, --extract archive dir
Extract the files from a package.
-X archive dir, --vextract archive dir
Extract and display the filenames from a package.
Options
--abort-after= num
Abort processing after num errors. Default is 50.
-B, --auto-deconfigure
When a package is removed, automatically deconfigure any other package that depended on it.
-Doctal, --debug= octal
Turn on debugging, with the octal value specifying the desired level of debugging information. Use -Dh
or --debug= help to display the possible values. You can OR the values to get the desired output.

-E, --skip-same-version
Don't install the package if this version is already installed.
--force-list, --no-force-list, --refuse-list
Force or refuse to force an operation. list is specified as a comma-separated item of options. With --force,
a warning is printed, but processing continues. --refuse and --no-force cause processing to stop with an
error. The force/ refuse options are:

architecture
Process even if intended for a different architecture.
auto-select
Select or deselect packages to install or remove them. Forced by default.

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bad-path
Some programs are missing from the path.
configure-any
Configure any unconfigured package that the package depends on.
conflicts
Permit installation of conflicting packages. Can result in problems from files being overwritten.
depends
Turn dependency problems into warnings.
depends-version
Warn of version problems when checking dependencies, but otherwise ignore.
downgrade
Install even if a newer version is already installed. Forced by default.
hold
Process packages even if they are marked to be held.
not-root
Try to install or remove even when not logged on as root.
overwrite
Overwrite a file from one package with the same file from another package. Forced by default.
overwrite-dir
Overwrite one package's directory with a file from another package.
overwrite-diverted
Overwrite a diverted file with an undiverted version.
remove-essential
Remove an essential package. Note that this can cause your system to stop working.
remove-reinstreq
Remove packages that are broken and are marked to require reinstallation.
-G
Don't install a package if a newer version is already installed. The same as --refuse-downgrade.

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--ignore-depends= pkglist

Dependency problems result only in a warning for the packages in pkglist.
--largemem
Specify that dpkg can use as much memory as it needs.
--new
New binary package format. This is a dpkg-deb option.
--no-act
Go through the motions, but don't actually write any changes. Used for testing. Be sure to specify before
the action; otherwise changes might be written.

--nocheck
Ignore the contents of the control file when building a package. This is a dpkg-deb option.
-O, --selected-only
Process only packages that are marked as selected for installation.
--old
Old binary package format. This is a dpkg-deb option.
-R, --recursive
Recursively handle .deb files found in the directories specified with -A, --install, --unpack, and --avail
and their subdirectories.

-R, --root= dir, --admindir= dir, --instdir= dir
Change default directories. admindir contains administrative files with status and other information
about packages; it defaults to /var/ lib/ dpkg. instdir is the directory in which packages are installed and
defaults to /. Changing the root directory to dir automatically changes instdir to dir and admindir to
/dir/ var/ lib/ dpkg.

--smallmem
Specify that dpkg should try to preserve memory.

dpkg-deb dpkg-deb action [options]
Backend command for building and managing Debian package archives. Also see dpkg; you'll often want to use
dpkg to pass commands through to dpkg-deb, rather than call dpkg-deb directly.

Actions
-b dir [archive], --build dir [archive]
Create an archive from the filesystem tree starting with directory dir. The directory must have a DEBIAN
subdirectory containing the control file and any other control information. If archive is specified and is a

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filename, the package is written to that file; if no archive is specified, the package is written to dir. deb. If
the archive already exists, it is replaced. If archive is the name of a directory, the dpkg-deb looks in the
control file for the information it needs to generate the package name. (Note that for this reason, you
cannot use --no-check with a directory name.)

-c archive, --contents archive
List the filesystem-tree portion of archive.
-e, --control archive dir
Extract control information from archive into the directory dir, which is created if it doesn't exist.
-f archive [control-fields], --field archive [control-fields]
Extract information about one or more fields in the control file for archive. If no fields are provided, print
the entire control file.

-h, --help
Print help information and exit.
-I archive [control-files], --info archive [control-files]
Provide information about binary package archive. If no control files are provided, print a summary of
the package contents; otherwise, print the control files in the order they were specified. An error message
is printed to standard error for any missing components.

--fsys-tarfile archive
Extract the filesystem tree from archive, and send it to standard output in tar format. Can be used with
tar to extract individual files from an archive.

--license
Print the license information and exit. Accepts the spelling --licence in addition to --license.
--version
Print the version number and exit.
-x archive dir, --extract archive dir
-X archive dir, --vextract archive dir

Extract the filesystem tree from archive into the specified directory, creating dir if it doesn't already exist.
-x (--extract) works silently, while -X (--vextract) lists the files as it extracts them. Do not use this
option to install packages; use dpkg instead.

Options
-D
Turn on debugging.
--new
Build a new-style archive format (this is the default).

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--no-check
Don't check the control file before building an archive. This lets you build a broken archive.
--old
Build an old-style archive format.

dpkg-split dpkg-split [action] [options]
Split a binary package into smaller pieces and reassemble the pieces, manually or in automatic mode. The
automatic mode maintains a queue of parts for reassembling. Useful for transferring to and from floppy disks.

Actions
-a -o output part, --auto -o output part
Add part to the queue for automatic reassembly and if all the parts are available, reassemble the package
as output.

-d [packages], --discard [packages]
Discard parts from the automatic-assembly queue. If any packages are specified, discard only parts from
those packages. Otherwise, empty the queue.

-I parts, --info parts
Print information about the part file or files specified.
-j parts, --join parts
Join the parts of a package file together from the parts specified. The default output file is package-version.
deb.

-l, --listq
List the contents of the queue of parts waiting for reassembly, giving the package name, the parts that are
on the queue, and the number of bytes.

-s full-package [prefix], --full-package [prefix]
Split the package full-package into parts, named prefixNofM. deb. The prefix defaults to the full-package
name without the .deb extension.

-h, --help
Print help message and exit.
--license
Print the license information and exit. Accepts the spelling --licence in addition to --license.
--version
Print the version information and exit.

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Options

--depotdir
Specify an alternate directory depotdir for the queue of parts waiting for reassembly. Default is
/var/ lib/ dpkg.

--msdos
Force --split output filenames to be MS-DOS-compatible.
-Q, --npquiet
Do not print an error message for a part that doesn't belong to a binary package when doing automatic
queuing or reassembly.

-o output, --output output
Use output as the filename for a reassembled package.
-S num, --partsize num
When splitting, specify the maximum part size (num) in kilobytes. Default is 450 KB.

dselect dselect [options] [action]
A screen-oriented user frontend to dpkg. The primary user interface for installing and managing packages. See
dpkg and dpkg-deb for information on building packages.

Actions
If dselect is run with no action specified on the command line, it displays the following menu:
* 0. [A] ccess Choose the access method to use. 1. [U] pdate Update list of available packages, if possible. 2. [S] elect Request which packages you want on your system. 3. [I] nstall Install and upgrade wanted packages. 4. [C] onfig Configure any packages that are unconfigured. 5. [R] emove Remove unwanted software. 6. [Q] uit Quit dselect.

The asterisk (on the first line here) shows the currently selected option. Any of the menu items can be specified
directly on the command line as an action (access, update, select, install, config, remove, quit) to go directly to
the desired activity. For example:

% dselect accessIf you enter quit on the command line, dselect exits immediately without doing anything. An additional
command-line action is menu, which displays the menu and is equivalent to omitting the action.

Options
--admindir dir
Change the directory that holds internal data files to dir. Default is /var/ lib/ dpkg.

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-D [file], --debug [file]

Turn on debugging. Send output to file if specified.
--help
Print help message and exit.
--license
Print the license information and exit. Accepts the spelling --licence in addition to --license.
--version
Print version information and exit.

5. Red Hat and Debian
Package Managers
6. The Linux Shells: An
Overview

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Linux in a Nutshell, 3rd
Edition

Chapter 6. The Linux Shells: An
Overview
Contents:
Purpose of the Shell
Shell Flavors
Common Features
Differing Features

The shell is a program that acts as a buffer between you and the operating system. In its role
as a command interpreter, it should (for the most part) act invisibly. It also can be used for
simple programming.

This section introduces three shells commonly used on Linux systems --the Bourne-Again
shell (bash), the C shell (csh), and csh's enhanced version, tcsh --and summarizes the major
differences between them. Details on them are provided in Chapter 7, "bash: The Bourne-Again

Shell", and Chapter 8, "csh and tcsh". (Some Linux distributions also offer the Korn
shell, ksh, another popular version of the Bourne shell with some of the same features as
bash.)

The following topics are presented in this chapter:
l Purpose of the shell
l Shell flavors
l Common features
l Differing features

6.1. Purpose of the Shell
There are three main uses for the shell:

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l Interactive use

l Customization of your Linux session
l Programming

6.1.1. Interactive Use
When the shell is used interactively, it waits for you to issue commands, processes them (to
interpret special characters, such as wildcards), and executes them. Shells also provide a set of
commands, known as built-ins, to supplement Linux commands.

6.1.2. Customization of Your Linux Session
A Linux shell defines variables, such as the locations of your home directory and mail spool,
to control the behavior of your session. Some variables are preset by the system; you can
define others in startup files that your shell reads when you log in. Startup files also can
contain Linux or shell commands, for execution immediately after login.

6.1.3. Programming
A series of individual commands (be they shell or other Linux commands available on the
system) combined into one executable file is called a shell script. Batch files in MS-DOS are a
similar concept. bash is considered a powerful programming shell, while scripting in csh is
rumored to be hazardous to your health.

5.2. The Debian Package
Manager
6.2. Shell Flavors

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6.2. Shell Flavors
Many different Linux shells are available. This book describes the three most popular shells:
l The Bourne-Again shell (bash), which is based on the Bourne shell (sh) and is
standard for Linux l
The C shell (csh), which uses C syntax and has many conveniences l
tcsh, an extension of csh that appears instead of csh in many Linux distributions

Most systems have more than one shell, and people will often use one shell for writing shell
scripts and another for interactive use.

When you log in, the system determines which shell to run by consulting your entry in
/etc/ passwd. The last field of each entry calls a program to run as the default shell. For
example:

Program Name Shell
/bin/ sh Bourne-Again shell
/bin/ bash Bourne-Again shell
/bin/ csh C shell (or tcsh)
/bin/ tcsh tcsh

You can change to another shell by typing the program name at the command line. For
example, to change from bash to tcsh, type:

$ exec tcsh

6. The Linux Shells: An
Overview
6.3. Common Features

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6.3. Common Features
The following table is a sampling of features that are common to bash, csh, and tcsh. Note
that tcsh is an enhanced version of csh; therefore, tcsh includes all features of csh, plus some
others.

Symbol/ Command Meaning/ Action
> Redirect output.
>> Append output to file.
< Redirect input.
<< ``Here'' document (redirect input).
| Pipe output.
& Run process in background.
; Separate commands on same line.
* Match any character( s) in filename.
? Match single character in filename.
!n Repeat command number n.
[ ] Match any characters enclosed.
( ) Execute in subshell.
` ` Substitute output of enclosed command.
" " Partial quote (allows variable and command expansion).
\ Quote following character.
$var Use value for variable.

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$$ Process ID.
$0 Command name.

$n nth argument (0< n 9).
$* All arguments.
# Begin comment.
bg Background execution.
break Break from loop statements.
cd Change directories.
continue Resume a program loop.
echo Display output.
eval Evaluate arguments.
exec Execute a new shell or other program.
fg Foreground execution.
jobs Show active jobs.
kill Terminate running jobs.
newgrp Change to a new group.
shift Shift positional parameters.
stop Suspend a background job.
suspend Suspend a foreground job.
umask Set or list permissions on files to be created.
unset Erase variable or function definitions.
wait Wait for a background job to finish.

6.2. Shell Flavors 6.4. Differing Features
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.
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6.4. Differing Features
The following table is a sampling of features that are different among the three shells:

Meaning/ Action bash csh tcsh
Default prompt. $ % %
Force redirection. >| >! >!Force append. >>! >>!Variable assignment. var= val set var= val set var= val
Set environment variable. export var= val setenv var val setenv var val
Number of arguments. $# $# argv $# argvExit status. $? $status $?Execute commands in file. . file source file source file
End a loop statement. done end endEnd case or switch. esac endsw endswLoop through variables. for/ do foreach foreach

Sample if statement. if [ $i -eq 5 ] if ($ i== 5) if ($ i== 5)End if statement. fi endif endifSet resource limits. ulimit limit limitRead from terminal. read $< $<Make a variable read-only. readonly set -r

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File inquiry operator; tests
for nonzero size. -s

Complete current word. Tab Tab
Ignore interrupts. trap 2 onintr onintrBegin until loop. until/ do until untilBegin while loop. while/ do while while

6.3. Common Features 7. bash: The Bourne-Again
Shell

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Linux in a Nutshell, 3rd
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Chapter 7. bash: The Bourne-Again Shell
Contents:
Overview of Features
Invoking the Shell
Syntax
Variables
Arithmetic Expressions
Command History
Built-in Commands
Job Control

This chapter presents the following topics:
l Overview of features

l Invoking the shell
l Syntax
l Variables
l Arithmetic expressions
l Command history
l Built-in commands
l Job control

7.1. Overview of Features
bash is the GNU version of the standard Bourne shell --the original Unix shell --and incorporates many popular features from
other shells such as csh, tcsh, and the Korn shell (ksh). Both tcsh, which is described in the following chapter, and ksh, which
offers many of the features in this chapter, also are available on most distributions of Linux. But bash is the standard Linux
shell, loaded by default when most user accounts are created.

If executed as part of the user's login, bash starts by executing any commands found in /etc/ profile. Then it executes the
commands found in ~/. bash_ profile, ~/. bash_ login, or ~/. profile (searching for each file only if the previous file is not found).
Many distributions change shell defaults in /etc/ profile for all users, even changing the behavior of common commands like ls.

In addition, every time it starts (as a subshell or a login shell), bash looks for a file named ~/. bashrc. Many system
administration utilities create a small ~/. bashrc automatically, and many users create quite large startup files. Any commands
that can be executed from the shell can be included. A small sample file may look like this; each feature can be found either in
this chapter or in Chapter 3, "Linux Commands":

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# Set bash variable to keep 50 commands in history. HSTSIZE= 50 # # Set prompt to show current working directory and history number of command. PS1= '\ w: Command \!$ ' # # Set path to search for commands in my personal directories, then standard ones. PATH=~/ bin:~/ scripts:$ PATH # # Keep group and others from writing my newly created files. umask 022 # # Show color-coded file types. alias ls= 'ls --color= yes' # # Make executable and .o files ugly yellow so I can find and delete them. export LS_ COLORS=" ex= 43:*. o= 43" # # Quick and dirty test of a single-file program. function gtst () { g++ -o $1 $1. C && ./$ 1 } # # Remove .o files. alias clean= 'find ~ -name \*. o -exec rm {} \; '

bash provides the following features:
l Input/ output redirection
l Wildcard characters (metacharacters) for filename abbreviation
l Shell variables for customizing your environment
l Powerful programming capabilities
l Command-line editing (using vi-or Emacs-style editing commands)
l Access to previous commands (command history)
l Integer arithmetic
l Arithmetic expressions
l Command name abbreviation (aliasing)
l Job control
l Integrated programming features
l Control structures
l Directory stacking (using pushd and popd)
l Brace/ tilde expansion
l Key bindings

6.4. Differing Features 7.2. Invoking the Shell
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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7.2. Invoking the Shell
The command interpreter for bash can be invoked as follows:
bash [options] [arguments]bash can execute commands from a terminal (when -i is specified), from a file (when the first
argument is an executable script), or from standard input (if no arguments remain or if -s is
specified).

7.2.1. Options
Options that appear here with double hyphens also work when entered with single hyphens,
but the double-hyphen versions are recommended because they are standard.

-, --
Treat all subsequent strings as arguments, not options.
--dump-po-strings

Same as --dump-strings but uses a special "portable object" format suitable for
scripting.
--dump-strings

For execution in non-English locales, dump all strings that bash translates.
-c str

Read commands from string str.
-i

Create an interactive shell (prompt for input).
--help

Print information about which version of bash is installed, plus a list of options.

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--login

Behave like a login shell; try to process /etc/ profile on startup. Then process
~/. bash_ profile, ~/. bash_ login, or ~/. profile (searching for each file only if the
previous file is not found).
--nobraceexpansion

Disable brace expansion.
--noediting

Disable line editing with arrow and control keys.
--noprofile

Do not process /etc/ profile, ~/. bash_ profile, ~/. bash_ login, or ~/. profile on startup.
--norc

Do not process ~/. bashrc on startup.
-p

Start up as a privileged user; don't process $HOME/. profile.
--posix

Conform to POSIX standard.
-r

Restrict users to a very secure, limited environment; for instance, they cannot change
out of the startup directory or use the > sign to redirect output.
--rcfile file

Substitute file for .bashrc on startup.
--restricted

Same as -r.
-s

Read commands from standard input; output from built-in commands goes to file
descriptor 1; all other shell output goes to file descriptor 2.
-v

Print each line as it is executed (useful for tracing scripts).
--verbose

Same as -v.
--version

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Print information about which version of bash is installed.
-x

Turn on debugging, as described under the -x option to the set built-in command.
-D

For execution in non-English locales, dump all strings that bash translates.
The remaining options to bash are listed under the set built-in command.

7.2.2. Arguments
Arguments are assigned, in order, to the positional parameters $1, $2, and so forth. If the first
argument is an executable script, commands are read from it and remaining arguments are
assigned to $1, $2, and so on.

7. bash: The Bourne-Again
Shell
7.3. Syntax

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Edition

7.3. Syntax
This subsection describes the many symbols peculiar to bash. The topics are arranged as follows:
l Special files
l Filename metacharacters
l Command-line editing
l Quoting
l Command forms
l Redirection forms
l Coprocesses

7.3.1. Special Files
File Purpose
/etc/ profile Executed automatically at login
$HOME/. bash_ profile Executed automatically at login
$HOME/. bashrc Executed automatically at shell startup
$HOME/. bash_ logout Executed automatically at logout
$HOME/. bash_ history Record of last session's commands
/etc/ passwd Source of home directories for ~name abbreviations

7.3.2. Filename Metacharacters
Characters Meaning
* Match any string of zero or more characters.
? Match any single character.
[abc...] Match any one of the enclosed characters; a hyphen can be used to specify a range (e. g., a-z, A-Z, 0-9).
[! abc...] Match any character not among the enclosed characters.
{str1,...} Brace expansion: match any of the enclosed strings.
~name HOME directory of user name.
~+ Current working directory (PWD).
~-Previous working directory from directory stack (OLDPWD, see also the pushd built-in command).
~+ n The nth entry in the directory stack, counting from the start of the list with the first entry being 0.
~-n The nth entry in the directory stack, counting from the end of the list with the last entry being 0.

Patterns can be a sequence of patterns separated by |; if any of the subpatterns match, the entire sequence is considered matching.

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This extended syntax resembles that available to egrep and awk.

7.3.2.1. Examples
$ ls new* List new and new. 1$ cat ch? Match ch9 but not ch10$ vi [D-R]* Match files that begin with uppercase D through R

7.3.3. Command-line Editing
Command lines can be edited like lines in either Emacs or vi. Emacs is the default. See Section 7.6.1, "Line-Edit Mode" later in
this chapter for more information.

vi mode has two submodes, insert mode and command mode. The default mode is insert; you can go to command mode by
pressing Esc. In command mode, typing a (append) or i (insert) will return you to insert mode.

Some users discover that the Del or Backspace key on the terminal does not delete the character before the cursor, as it should.
Sometimes the problem can be solved by issuing one of the following commands (or placing it in your .bashrc file):

stty erase ^? stty erase ^H

See the stty command in Chapter 3, "Linux Commands" for more information. On the X Window System, an alternative solution
is to use the xmodmap command, but this cannot be described easily here because it requires you to do some research about your
terminal.

Table 7-1 through Table 7-14 show various Emacs and vi commands.

Table 7-1. Basic Emacs-Mode Commands

Command Description
Ctrl-B Move backward one character (without deleting).
Ctrl-F Move forward one character.
Del Delete one character backward.
Ctrl-D Delete one character forward.

Table 7-2. Emacs-Mode Word Commands
Command Description
Esc b Move one word backward.
Esc f Move one word forward.
Esc Del Kill one word backward.
Esc d Kill one word forward.
Ctrl-Y Retrieve (yank) last item killed.

Table 7-3. Emacs-Mode Line Commands
Command Description
Ctrl-A Move to beginning of line.

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Ctrl-E Move to end of line.
Ctrl-K Kill forward to end of line.

Table 7-4. Emacs-Mode Commands for Moving Through the History File
Command Description
Ctrl-P Move to previous line.
Ctrl-N Move to next line.
Ctrl-R Search backward.
Esc < Move to first line of history file.
Esc > Move to last line of history file.

Table 7-5. Completion Commands
Command Description
Tab Attempt to perform general completion of the text.
Esc ? List the possible completions.
Esc / Attempt filename completion.
Ctrl-X / List the possible filename completions.
Esc ~ Attempt username completion.
Ctrl-X ~ List the possible username completions.
Esc $ Attempt variable completion.
Ctrl-X $ List the possible variable completions.
Esc @ Attempt hostname completion.
Ctrl-X @ List the possible hostname completions.
Esc ! Attempt command completion.
Ctrl-X ! List the possible command completions.
Esc Tab Attempt completion from previous commands in the history list.

Table 7-6. Emacs-Mode Miscellaneous Commands
Command Description
Ctrl-J Same as Return.
Ctrl-L Clear the screen, placing the current line at the top of the screen.
Ctrl-M Same as Return.
Ctrl-O Same as Return, then display next line in command history.
Ctrl-T Transpose character left of and under the cursor.
Ctrl-U Kill the line from the beginning to point.
Ctrl-V Insert keypress instead of interpreting it as a command.

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Ctrl-[ Same as Esc (most keyboards).
Esc c Capitalize word under or after cursor.
Esc u Change word under or after cursor to all capital letters.
Esc l Change word under or after cursor to all lowercase letters.
Esc . Insert last word in previous command line after point.
Esc _ Same as Esc.

Table 7-7. Editing Commands in vi Input Mode
Command Description
Del Delete previous character.
Ctrl-W Erase previous word (i. e., erase until a blank).
Ctrl-V Insert keypress instead of interpreting it as a command.
Esc Enter control mode (see Table 7-8).

Table 7-8. Basic vi Control Mode Commands
Command Description
h Move left one character.
l Move right one character.
b Move left one word.
w Move right one word.
B Move to beginning of preceding nonblank word.
W Move to beginning of next nonblank word.
e Move to end of current word.
E Move to end of current nonblank word.
0 Move to beginning of line.
^ Move to first nonblank character in line.
$ Move to end of line.

Table 7-9. Commands for Entering vi Input Mode
Command Description
i Insert text before current character (insert).
a Insert text after current character (append).
I Insert text at beginning of line.
A Insert text at end of line.
r Replace current character with this text.
R Overwrite existing text.

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Table 7-10. Some vi-Mode Deletion Commands
Command Description
dh Delete one character backward.
dl Delete one character forward.
db Delete one word backward.
dw Delete one word forward.
dB Delete one nonblank word backward.
dW Delete one nonblank word forward.
d$ Delete to end-of-line.
d0 Delete to beginning of line.

Table 7-11. Abbreviations for vi-Mode Delete Commands
Command Description
D Delete to end of line (equivalent to d$).
dd Delete entire line (equivalent to 0d$).
C Delete to end of line; enter input mode (equivalent to c$).
cc Delete entire line; enter input mode (equivalent to 0c$).
X Delete character backward (equivalent to dl).
x Delete character forward (equivalent to dh).

Table 7-12. vi Control Mode Commands for Searching the Command History
Command Description
k or -Move backward one line.
j or + Move forward one line.
G Move to line given by repeat count.
/string Search backward for string.
?string Search forward for string.
n Repeat search in same direction as previous.
N Repeat search in opposite direction of previous.

Table 7-13. vi-Mode Character-Finding Commands
Command Description
fx Move right to next occurrence of x.
Fx Move left to previous occurrence of x.
tx Move right to next occurrence of x, then back one space.

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Tx Move left to previous occurrence of x, then forward one space.
; Redo last character-finding command.
, Redo last character-finding command in opposite direction.

Table 7-14. Miscellaneous vi-Mode Commands
Command Description
~ Invert (toggle) case of current character( s).
-Append last word of previous command; enter input mode.
Ctrl-L Clear the screen and redraw the current line on it; good for when your screen becomes garbled.

# Prepend # (comment character) to the line and send it to the history file; useful for saving a command to be executed later, without having to retype it.

7.3.4. Quoting
Quoting disables a character's special meaning and allows it to be used literally, as itself. The following characters have special
meaning to bash:

Character Meaning
; Command separator
& Background execution
( ) Command grouping (enter a subshell)
{ } Command block
| Pipe
> < & Redirection symbols
* ? [ ] ~ ! Filename metacharacters
" ' \ Used in quoting other characters
` Command substitution
$ Variable substitution (or command substitution)
newline space tab Word separators
# Comment

The following characters can be used for quoting:
Character Action

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" "Everything between " and " is taken literally, except for the following characters that keep their special meaning:
$Variable substitution will occur.
`

Command substitution will occur.
"

This marks the end of the double quote.

' ' Everything between ' and ' is taken literally, except for another '.\ The character following a \ is taken literally. Use within " " to escape ", $, and `. Often used to escape itself, spaces, or newlines.

7.3.4.1. Examples
$ echo 'Single quotes "protect" double quotes'Single quotes "protect" double quotes

$ echo "Well, isn't that \" special\"?"Well, isn't that "special"?

$ echo "You have `ls| wc -l` files in `pwd`"You have 43 files in /home/ bob

$ echo "The value of \$ x is $x"The value of $x is 100

7.3.5. Command Forms

Syntax Effect
cmd & Execute cmd in background.
cmd1 ; cmd2 Command sequence; execute multiple cmds on the same line.
(cmd1 ; cmd2) Subshell; treat cmd1 and cmd2 as a command group.
cmd1 | cmd2 Pipe; use output from cmd1 as input to cmd2.
cmd1 `cmd2` Command substitution; use cmd2 output as arguments to cmd1.
cmd1 $( cmd2) Command substitution; nesting is allowed.
cmd1 && cmd2 AND; execute cmd2 only if cmd1 succeeds.
cmd1 || cmd2 OR; execute cmd2 only if cmd1 fails.
{ cmd1 ; cmd2 } Execute commands in the current shell.

7.3.5.1. Examples
$ nroff file & Format in the background $cd; ls Execute sequentially $(date; who; pwd) > logfile All output is redirected $sort file | pr -3 | lp Sort file, page output, then print $vi `grep -l ifdef *. c` Edit files found by grep $egrep '( yes| no) ' `cat list` Specify a list of files to search

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$ egrep '( yes| no) ' $( cat list) Same as previous using bash command substitution $egrep '( yes| no) ' $(< list) Same, but faster $grep XX file && lp file Print file if it contains the pattern $grep XX file || echo "XX not found" Echo an error message if the pattern is not found

7.3.6. Redirection Forms

File Descriptor Name Common Abbreviation Typical Default
0 Standard input stdin Keyboard
1 Standard output stdout Screen
2 Standard error stderr Screen

The usual input source or output destination can be changed as shown in Table 7-15.
Table 7-15. I/ O Redirectors

Redirector Function
> file Direct standard output to file.
< file Take standard input from file.
cmd1 | cmd2 Pipe; take standard output of cmd1 as standard input to cmd2.
>> file Direct standard output to file; append to file if it already exists.
>| file Force standard output to file even if noclobber is set.
n>| file Force output from the file descriptor n to file even if noclobber is set.
<> file Use file as both standard input and standard output.

<< text
Read standard input up to a line identical to text (text can be stored in a shell variable). Input is usually typed on
the screen or in the shell program. Commands that typically use this syntax include cat, echo, ex, and sed. If
text is enclosed in quotes, standard input will not undergo variable substitution, command substitution, etc.

n> file Direct file descriptor n to file.
n< file Set file as file descriptor n.
>& n Duplicate standard output to file descriptor n.
<& n Duplicate standard input from file descriptor n.
&> file Direct standard output and standard error to file.
<&-Close the standard input.
>&-Close the standard output.
n>&-Close the output from file descriptor n.
n<&-Close the input from file descriptor n.

7.3.6.1. Examples
$ cat part1 > book$ cat part2 part3 >> book$ mail tim < report

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$ grep Chapter part* 2> error_ file

$ sed 's/^/ XX /' << END_ ARCHIVE> This is often how a shell archive is "wrapped",> bundling text for distribution. You would normally> run sed from a shell program, not from the command line.> END_ ARCHIVEXX This is often how a shell archive is "wrapped", XX bundling text for distribution. You would normally XX run sed from a shell program, not from the command line.

To redirect standard output to standard error:
$ echo "Usage error: see administrator" 1>& 2The following command sends output (files found) to filelist and sends error messages (inaccessible files) to file no_ access:
$ find / -print > filelist 2> no_ access

7.3.7. Coprocesses
Coprocesses are a feature of bash and do not appear in other shells.

Syntax Effect
cmd1 | cmd2 |& Coprocess; execute the pipeline in the background. The shell sets up a two-way pipe, allowing redirection of both standard input and standard output.

read -p var Read coprocess input into variable var.
print -p string Write string to the coprocess.
cmd <& p Take input for cmd from the coprocess.
cmd >& p Send output of cmd to the coprocess.

7.3.7.1. Examples
cat memo Print contents of file Sufficient unto the day is A word to the wise.ed -memo |& Start coprocessprint -p /word/ Send ed command to coprocessread -p search Read output of ed command into variable searchprint "$ search" Show the line on standard output A word to the wise.

7.2. Invoking the Shell 7.4. Variables
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Edition

7.4. Variables
Variables are prefaced by a dollar sign ($) and optionally enclosed in braces ({}). You can
assign a value to a variable through an equals sign (=); no whitespace can appear on either
side of the equals sign:

$ TMP= temp. fileBy default, variables are seen only within the shell itself; to pass variables to other programs
invoked within the shell, see the export built-in command.

If subscripted by brackets ([]), the variable is considered an array variable. For instance:
$ DIR_ LIST[ 0]= src$ DIR_ LIST[ 1]= headers$ ls ${ DIR_ LIST[ 1]}

The contents of headers are listed. Many substitutions and commands in this chapter handle
arrays by operating on each element separately.

This subsection describes:
l Variable substitution

l Built-in shell variables

7.4.1. Variable Substitution
In the following substitutions, braces ({ }) are optional, except when needed to separate a
variable name from following characters that would otherwise be considered part of the name.

Variable Meaning
${ var} The value of variable var.

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$0 Name of the program.

${ n}
Individual arguments on command line (positional parameters); 1 n

9.
$# Number of arguments on command line.
$* All arguments on command line.

$@ Same as $* but contents are split into words when the variable is enclosed in double quotes.

$$ Process number of current shell; useful as part of a filename for creating temporary files with unique names.
$? Exit status of last command (normally 0 for success).
$! Process number of most recently issued background command.

$-Current execution options (see the set built-in command). By default, hB for scripts and himBH for interactive shells.

$_ Initially set to name of file invoked for this shell, then set for each command to the last word of the previous command.

Table 7-16 through Table 7-18 show various types of operators that can be used with bash
variables.

Table 7-16. Substitution Operators

Operator Substitution
${ varname:-word} If varname exists and isn't null, return its value; otherwise, return word.
Purpose: Returning a default value if the variable is undefined.
Example: ${ count:-0} evaluates to 0 if count is undefined.

${ varname:= word}
If varname exists and isn't null, return its value; otherwise set it to
word and then return its value. Positional and special parameters
cannot be assigned this way.

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Purpose: Setting a variable to a default value if it is undefined.
Example: ${ count:= 0} sets count to 0 if it is undefined.

${ varname:? message}
If varname exists and isn't null, return its value; otherwise, print
varname: followed by message, and abort the current command or
script (noninteractive shells only). Omitting message produces the
default message "parameter null or not set."

Purpose: Catching errors that result from variables being undefined.

Example: {count:?" undefined!"} prints ``count: undefined! '' and exits if count is undefined.

${ varname:+ word} If varname exists and isn't null, return word; otherwise, return null.
Purpose: Testing for the existence of a variable.
Example: ${ count:+ 1} returns 1 (which could mean true) if count is defined.
${# varname} Return the number of characters in varname.
Purpose: Preparing for substitution or extraction of substrings.
Example: If ${ USER} currently expands to root, ${# USER} expands to 4.

Table 7-17. Pattern-Matching Operators
Operator Meaning
${ variable# pattern} If the pattern matches the beginning of the variable's value, delete the shortest part that matches and return the rest.

${ variable## pattern} If the pattern matches the beginning of the variable's value, delete the longest part that matches and return the rest.
${ variable% pattern} If the pattern matches the end of the variable's value, delete the shortest part that matches and return the rest.
${ variable%% pattern} If the pattern matches the end of the variable's value, delete the longest part that matches and return the rest.

${ var/ pat/ sub}
Return var with the first occurrence of pat replaced by sub. Can
be applied to $* or $@, in which case each word is treated
separately. If pat starts with # it can match only the start of var; if
pat ends with % it can match only the end of var.

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${ var// pat/ sub} Return var with the every occurrence of pat replaced by sub.

${ variable: n} Truncate the beginning of the variable and return the part starting with character number n, where the first character is 0.

${ variable: n: l} Starting with character number n, where the first character is 0, return a substring of length l from the variable.

Table 7-18. Expression Evaluation
Operator Meaning
$(( arithmetic-expression)) Return the result of the expression. Arithmetic operators are described under "Arithmetic Expressions."

Example:
TODAY= 'date +%-d' ; echo $(($ TODAY+ 7)) stores the
number of the current day in $TODAY and then prints that
number plus 7 (the number of the same day next week).

[[$ condition]] Return 1 if condition is true and 0 if it is false. Conditions are described under the test built-in command.

7.4.2. Built-in Shell Variables
Built-in variables are set automatically by the shell and typically are used inside shell scripts.
Built-in variables can make use of the variable substitution patterns already shown earlier.
When setting variables, you do not include dollar signs, but when referencing their values
later, the dollar signs are necessary.

Tables Table 7-19 through Table 7-22 show the commonly used built-in variables in bash.

Table 7-19. Behavior-Altering Variables

Variable Meaning

auto_ resume
Allows a background job to be brought to the foreground
simply by entering a substring of the job's command line;
values can be substring (resume if the user's string matches
part of the command); exact (string must exactly match
command); or another value (string must match at beginning of
command).

BASH_ ENV Startup file of commands to execute, if bash is invoked to run a script.

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CDPATH Colon-separated list of directories to search for the directory passed in a cd command.
EDITOR Pathname of your preferred text editor.
IFS Word separator; used by shell to parse commands into their elements.

IGNOREEOF If nonzero, don't allow use of a single Ctrl-D (the end-of-file or EOF character) to log off; use the exit command to log off.
PATH Colon-separated list of directories to search for each command.
PROMPT_ COMMAND Command that bash executes before issuing a prompt for a new command.

PS1
Prompt displayed before each new command; see the later
section Section 7.6.4, "Variables in Prompt" for ways to

introduce dynamically changing information such as the
current working directory or command history number into the
prompt.

PS2 Prompt displayed before a new line if a command is not finished.
PS3 Prompt displayed by select built-in command.

PS4 Prompt displayed by -x debugging (see Section 7.2, "Invoking the Shell"). and the set built-in command).

Table 7-20. History Variables
Variable Meaning
FCEDIT Pathname of editor to use with the fc command.
HISTCMD The history number of the current command.

HISTCONTROL
If HISTCONTROL is set to the value of ignorespace, lines beginning
with a space are not entered into the history list. If set to ignoredups,
lines matching the last history line are not entered. Setting it to
ignoreboth enables both options.

HISTFILE Name of history file, on which the editing modes operate.

HISTFILESIZE The maximum number of lines to store in the history file. The default is 500.

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HISTSIZE The maximum number of commands to remember in the command history. The default is 500.

Table 7-21. Mail Variables
Variable Meaning
MAIL Name of file to check for incoming mail.
MAILCHECK How often, in seconds, to check for new mail (default is 60 seconds).
MAILPATH List of filenames, separated by colons (:), to check for incoming mail.

Table 7-22. Status Variables
Variable Meaning
BASH Pathname of this instance of the shell you are running.
BASH_ VERSION The version number of the shell you are running.
COLUMNS The number of columns your display has.
DIRSTACK List of directories manipulated by pushd and popd commands.

EUID Effective user ID of process running this shell, in the form of the number recognized by the system.

GROUPS Groups to which user belongs, in the form of the numbers recognized by the system.
HOME Name of your home (login) directory.
HOSTNAME Host the shell is running on.

HOSTTYPE Short name indicating the type of machine the shell is running on; for instance, i486.
LINES The number of lines your display has.
MACHTYPE Long string indicating the machine the shell is running on; for instance, i486-pc-linux-gnu.
OLDPWD Previous directory before the last cd command.
OSTYPE Short string indicating the operating system; for instance, "linux-gnu."

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PPID Process ID of parent process that invoked this shell.
PWD Current directory.
SECONDS Number of seconds since the shell was invoked.
SHELL Pathname of the shell you are running.
SHLVL Depth to which running shells are nested.
TERM The type of terminal that you are using.

UID Real user ID of process running this shell, in the form of the number recognized by the system.

7.3. Syntax 7.5. Arithmetic Expressions
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Linux in a Nutshell, 3rd
Edition

7.5. Arithmetic Expressions
The let command performs integer arithmetic. bash provides a way to substitute integer
values (for use as command arguments or in variables); base conversion is also possible:

Expression Meaning
(( expr)) Use the value of the enclosed arithmetic expression.

7.5.1. Operators
bash uses arithmetic operators from the C programming language; the following list is in
decreasing order of precedence. Use parentheses to override precedence.

Operator Meaning
-Unary minus
! ~ Logical negation; binary inversion (one's complement)
* / % Multiplication; division; modulus (remainder)
+ -Addition; subtraction
<< >> Bitwise left shift; bitwise right shift
<= >= Less than or equal to; greater than or equal to
< > Less than; greater than
== != Equality; inequality (both evaluated left to right)
& Bitwise AND
^ Bitwise exclusive OR
| Bitwise OR

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&& Logical AND
|| Logical OR
= Assign value.
+= -= Reassign after addition/ subtraction
*= /= %= Reassign after multiplication/ division/ remainder
&= ^= |= Reassign after bitwise AND/ XOR/ OR
<<= >>= Reassign after bitwise shift left/ right

7.5.2. Examples
See the let built-in command for more information and examples.
let "count= 0" "i = i + 1" Assign i and countlet "num % 2" Test for an even number

7.4. Variables 7.6. Command History
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Command History (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

7.6. Command History
bash lets you display or modify previous commands. This is similar to the C shell's history mechanism. Commands in the history list
can be modified using:

l Line-edit mode
l The fc command

In addition, the command substitutions described in Chapter 8, "csh and tcsh", also work in bash.

7.6.1. Line-Edit Mode
Line-edit mode lets you emulate many features of the vi or Emacs editors. The history list is treated like a file. When the editor is
invoked, you type editing keystrokes to move to the command line you want to execute. Arrow keys work on most terminals in both
Emacs mode and vi command mode. You also can change the line before executing it. See Table 7-23 for some examples of common

line-edit commands. When you're ready to issue the command, press Return.

The default line-edit mode is Emacs. To enable vi mode, enter:
$ set -o viNote that vi starts in input mode; to type a vi command, press Esc first.
The mode you use for editing bash commands is an entirely separate choice from the editor that is invoked for you automatically
within many commands (for instance, the editor mail readers invoke when you ask them to create a new mail message). To change the
default editor, set the VISUAL or EDITOR variable to the filename or full pathname of your favorite editor:

$ export EDITOR= emacsTable 7-23. Common Editing Keystrokes

vi Emacs Result
k Ctrl-P Get previous command.
j Ctrl-N Get next command.
/string Ctrl-R string Get previous command containing string.
h Ctrl-B Move back one character.
l Ctrl-F Move forward one character.
b Esc B Move back one word.
w Esc F Move forward one word.
X Del Delete previous character.
x Ctrl-D Delete one character.
dw Esc D Delete word forward.
db Esc H Delete word back.

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xp Ctrl-T Transpose two characters.

7.6.2. The fc Command
Use fc -l to list history commands and fc -e to edit them. See the entry under built-in commands for more information.

7.6.2.1. Examples
$ history List the last 16 commands $fc -l 20 30 List commands 20 through 30 $fc -l -5 List the last five commands $fc -l cat List the last command beginning with cat $fc -ln 5 > doit Save command 5 to file doit $fc -e vi 5 20 Edit commands 5 through 20 using vi $fc -e emacs Edit previous command using Emacs $!! Reexecute previous command $!cat Reexecute last cat command $!cat foo-file Reexecute last command, adding foo-file to the end of the argument list

7.6.3. Command Substitution

Syntax Meaning
! Begin a history substitution.
!! Previous command.
!N Command number N in history list.
!-N Nth command back from current command.
!string Most recent command that starts with string.
!? string? Most recent command that contains string.
!? string?% Most recent command argument that contains string.
!$ Last argument of previous command.
!# The current command up to this point.
!! string Previous command, then append string.
!N string Command N, then append string.
!{ s1} s2 Most recent command starting with string s1, then append string s2.
^old^ new^ Quick substitution; change string old to new in previous command; execute modified command.

7.6.4. Variables in Prompt
Using the following variables, you can display information about the current state of the shell or the system in your bash prompt. Set
the PS1 variable to a string including the desired variables. For instance, the following command sets PS1 to a string that includes the
\w variable in order to display the current working directory and the \! variable in order to display the number of the current
command. The next line is the prompt displayed by the change.

$ PS1= '\ w: Command \!$ '~/ book/ linux: Command 504$

Some of the prompt variables are relatively new, such as \j and \l, so they may not be supported in your version of bash.

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Variable Meaning
\a Alarm (bell)
\d Date in the format "Mon May 8"
\e Escape character (terminal escape, not backslash)
\h Hostname
\j Number of background jobs (active or stopped)
\l Current terminal name
\n Newline inserted in the prompt
\r Carriage return inserted in the prompt
\s Current shell
\t Time in 24-hour format, where 3: 30 p. m. appears as 15: 30: 00
\u User's account name
\v Version and release of bash
\w Current working directory
\H Like \h
\T Time in 12-hour format, where 3: 30 p. m. appears as 03: 30: 00
\V Version, release, and patch level of bash
\W Last element (following last slash) of current working directory
\\ Single backslash inserted in the prompt
\! Number of current command in the command history
\# Number of current command, where numbers started at 1 when the shell started
\@ Time in 12-hour format, where 3: 30 P. M. appears as 03: 30 p. m.
\$ Indicates whether you are root: displays # for root, $ for other users
\[ Starts a sequence of nonprinting characters, to be ended by \]
\] Ends the sequence of nonprinting characters started by \[
\nnn The character in the ASCII set corresponding to the octal number nnn inserted into the prompt

7.5. Arithmetic Expressions 7.7. Built-in Commands
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Linux in a Nutshell, 3rd
Edition

7.7. Built-in Commands
Examples to be entered as a command line are shown with the $ prompt. Otherwise, examples should be treated as code fragments that might
be included in a shell script. For convenience, some of the reserved words used by multiline commands also are included.

# #
Ignore all text that follows on the same line. # is used in shell scripts as the comment character and is not really a command.

#! #! shell
Used as the first line of a script to invoke the named shell (with optional arguments). Some older, non-Linux systems do not
support scripts starting with this line. For example:

#!/ bin/ bash

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: :
Null command. Returns an exit status of 0. Sometimes used as the first character in a file to denote a bash script. Shell variables
can be placed after the : to expand them to their values.

Example
Check whether someone is logged in:
if who | grep $1 > /dev/ null then : # do nothing # if pattern is found else echo "User $1 is not logged in" fi

. . file [arguments]
Same as source.

alias alias [-p] [name[= 'cmd']]Assign a shorthand name as a synonym for cmd. If ='cmd' is omitted, print the alias for name; if name also is omitted or if [-p]
is specified, print all aliases. See also unalias.

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bg bg [jobIDs]
Put current job or jobIDs in the background. See Section 7.8, "Job Control" later in this chapter.

bind bind [options]
bind [options] key: function
Print or set the bindings that allow keys to invoke functions such as cursor movement and line editing. Typical syntax choices
for keys are "\ C-t" for Ctrl-T and "\ M-t" or "\ et" for Esc T (quoting is needed to escape the sequences from the shell).
Function names can be seen though the -l option.

Options
-f filename
Consult filename for bindings, which should be in the same format as on the bind command line.
-l
Print all Readline functions, which are functions that can be bound to keys.
-m keymap
Specify a keymap for this and further bindings. Possible keymaps are emacs, emacs-standard, emacs-meta, emacs-ctlx,
vi, vi-move, vi-command, and vi-insert.

-p
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Display all functions and the keys that invoke them, in the format by which keys can be set.
-q function
Display the key bindings that invoke function.
-r key
Remove the binding attached to key, so it no longer works.
-s
Display all macros and the keys that invoke them, in the format by which keys can be set.
-u function
Remove all the bindings attached to function, so no keys will invoke it.
-v
Display all Readline variables (settings that affect history and line editing) and their current settings, in the format by
which variables can be set.

-x key: command
Bind key to a shell command (recent; not in all bash versions in common use).
-P
Display all bound keys and the functions they invoke.
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-S
Display all macros and the keys that invoke them.
-V
Display all Readline variables (settings that affect history and line editing) and their current settings.
Example
Bind Ctrl-T to copy-forward-word, the function that copies the part of the word following the cursor so it can be repasted:
$ bind "\ C-t": copy-forward-word

break break [n]
Exit from the innermost (most deeply nested) for, while, or until loop, or from the n innermost levels of the loop. Also exits
from a select list.

builtin builtin command [arguments]
Execute command, which must be a shell built-in. Useful for invoking built-ins within scripts of the same name.

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case case string
in
regex)
commands
;;
...
esac
If string matches regular expression regex, perform the following commands. Proceed down the list of regular expressions until
one is found (to catch all remaining strings, use * as regex at the end).

cd cd [dir&]
With no arguments, change to home directory of user. Otherwise, change working directory to dir. If dir is a relative pathname
but is not in the current directory, then the CDPATH variable is searched.

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command command [options] command [arguments]
Execute command; do not perform function look-up (i. e., refuse to run any command that is neither in PATH nor a built-in). Set
exit status to that returned by command, unless command cannot be found, in which case exit with a status of 127.

-p
Search default path, ignoring the PATH variable's value.
--
Treat everything that follows as an argument, not an option.

continue continue [n]
Skip remaining commands in a for, while, or until loop, resuming with the next iteration of the loop (or skipping n loops).

declare declare [options] [name[= value]]
typeset [options] [name[= value]]
Print or set variables. Options prefaced by + instead of -are inverted in meaning.
-a
Treat the following names as array variables.
-f
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Treat the following names as functions.
-i
Expect variable to be an integer, and evaluate its assigned value.
-p
Print names and settings of all shell variables and functions; take no other action.
-r
Do not allow variables to be reset later.
-x
Mark variables for subsequent export.
-F
Print names of all shell functions; take no other action.

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dirs dirs [options]
Print directories currently remembered for pushd/ popd operations.
Options
+entry
Print entryth entry (list starts at 0).
-entry
Print entryth entry from end of list.
-l
Long listing.

disown disown [options] [jobIDs]
Let job run, but disassociate it from the shell. By default, do not even list the job as an active job; commands like jobs and fg
will no longer recognize it. When -h is specified, the job is recognized but simply is kept from being killed when the shell dies.

Options
-a
Act on all jobs.
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-h
Do not pass a SIGHUP signal received by the shell on to the job.

echo echo [options] [string]
Write string to standard output, terminated by a newline. If no string is supplied, echo a newline. In bash, echo is just an alias
for print -. (See also echo in Chapter 3, "Linux Commands").

-e
Enable interpretation of escape characters:
\a
Audible alert
\b

Backspace
\c

Suppress the terminating newline (same as -n)
\f

Form feed
\n

Newline
\r

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Carriage return
\t

Horizontal tab
\v

Vertical tab
\\

Backslash
\nnn

The character in the ASCII set corresponding to the octal number nnn.
\xnnn

The character in the ASCII set corresponding to the hexadecimal number nnn.
-n

Do not append a newline to the output.
-E

Disable interpretation of escape characters.

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enable enable [options] [built-in ...]
Enable (or when -n is specified, disable) built-in shell commands. Without built-in argument or with -p option, print enabled
built-ins. With -a, print the status of all built-ins. You can disable shell commands in order to define your own functions with
the same names.

Options
-a
Display all built-ins, both enabled and disabled.
-n builtin

Disable builtin.
-p

Display enabled built-ins.
-s

Restrict display to special built-ins defined by POSIX standard.

eval eval [command args...]
Perform command, passing args.

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exec exec [options] [command]
Execute command in place of the current process (instead of creating a new process). exec also is useful for opening, closing, or
copying file descriptors.

Options
-a name
Tell command that it was invoked as name.
-c
Remove all environment variables from the process when the new command runs.
-l
Treat the new process as if the user were logging in.
Examples
$ trap 'exec 2>&-' 0 Close standard error when shell script exits (signal 0) $exec /bin/ tcsh Replace current shell with extended C shell $exec < infile Reassign standard input to infile

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exit exit [n]
Exit a shell script with status n (e. g., exit 1). n can be zero (success) or nonzero (failure). If n is not given, exit status will be that
of the most recent command. exit can be issued at the command line to close a window (log out).

Example
if [ $# -eq 0 ]; then echo "Usage: $0 [-c] [-d] file( s)" exit 1 # Error status fi

export export [options] [variables]
export [options] [name=[ value]]...
Pass (export) the value of one or more shell variables, giving global meaning to the variables (which are local by default). For
example, a variable defined in one shell script must be exported if its value will be used in other programs called by the script. If
no variables are given, export lists the variables exported by the current shell. If name and value are specified, assign value to a
variable name.

Options
--
Treat all subsequent strings as arguments, not options.
-f

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Expect variables to be functions.
-n
Unexport variable.
-p
List variables exported by current shell.

fc fc [options] [first] [last]
fc -e -[old= new] [command]
Display or edit commands in the history list. (Use only one of -l or -e.) fc provides capabilities similar to the C shell's history
and ! syntax. first and last are numbers or strings specifying the range of commands to display or edit. If last is omitted, fc
applies to a single command (specified by first). If both first and last are omitted, fc edits the previous command or lists the last
16. The second form of fc takes a history command, replaces old string with new string, and executes the modified command. If
no strings are specified, command is just reexecuted. If no command is given either, the previous command is reexecuted.
command is a number or string like first. See examples under Section 7.6, "Command History".

Options
-e [editor]
Invoke editor to edit the specified history commands. The default editor is set by the shell variable FCEDIT.
-l [first last]

List the specified command or range of commands, or list the last 16.
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-n
Suppress command numbering from the -l listing.
-r

Reverse the order of the -l listing.
-s pattern= newpattern

Edit command( s), replacing all occurrences of pattern with newpattern. Then reexecute.

fg fg [jobIDs]
Bring current job or jobIDs to the foreground. See Section 7.8, "Job Control".

for for x [in list]
do
commands
done
Assign each word in list to x in turn and execute commands. If list is omitted, $@ (positional parameters) is assumed.
Examples
Paginate all files in the current directory; save each result:

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for file in * do pr $file > $file. tmp done

Search chapters for a list of words (like fgrep -f):
for item in `cat program_ list` do echo "Checking chapters for" echo "references to program $item..." grep -c "$ item.[ co]" chap* done

function function command
{
...
}
Define a function. Refer to arguments the same way as positional parameters in a shell script ($ 1, etc.) and terminate with }.

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getopts getopts string name [args]
Process command-line arguments (or args, if specified) and check for legal options. getopts is used in shell script loops and is
intended to ensure standard syntax for command-line options. string contains the option letters to be recognized by getopts
when running the shell script. Valid options are processed in turn and stored in the shell variable name. If an option letter is
followed by a colon, the option must be followed by one or more arguments.

hash hash [-r] [commands]
Search for commands and remember the directory in which each command resides. Hashing causes the shell to remember the
association between a "name" and the absolute pathname of an executable, so that future executions don't require a search of
PATH. With no arguments, hash lists the current hashed commands. The display shows hits (the number of times the command
is called by the shell) and command (the full pathname).

help help [-s] [string]
Print help text on all built-in commands or those matching string. With -s, display only brief syntax, otherwise display summary
paragraph also.

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history history [options]
history [lines]
Print a numbered command history, denoting modified commands with a *. Include commands from previous sessions. You
may specify how many lines of history to print.

Options
-a [file]
bash maintains a file called .bash_ history in the user's home directory, a record of previous sessions' commands. Ask
bash to append the current session's commands to .bash_ history or to file.
-c

Clear history list: remove all previously entered commands from the list remembered by the shell.
-n [file]

Append to the history list those lines in the .bash_ history file or in file that have not yet been included.
-r [file]

Use .bash_ history or file as the history list, instead of the working history list.
-s command

Add command to working history list without executing it.
-w [file]

Overwrite .bash_ history or file with working history list.

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if if test-cmds
Begin a conditional statement. Possible formats are:
if test-cmds if test-cmds if test-cmdsthen then thencmds1 cmds1 cmds1fi else elif test-cmds cmds2then ficmds2... elsecmdsnfi

Usually, the initial if and any elif lines execute one test or [] command (although any series of commands is permitted). When if
succeeds (that is, the last of its test-cmds returns 0), cmds1 are performed; otherwise each succeeding elif or else line is tried.

jobs jobs [options] [jobIDs]
List all running or stopped jobs, or those specified by jobIDs. For example, you can check whether a long compilation or text
format is still running. Also useful before logging out. See also Section 7.8, "Job Control" later in this chapter.

Options
-l
List job IDs and process group IDs.
-n

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List only jobs whose status changed since last notification.
-p

List process group IDs only.
-r

List active, running jobs only.
-s

List stopped jobs only.
-x command [arguments]

Execute command. If jobIDs are specified, replace them with command.

kill kill [options] IDs
Terminate each specified process ID or job ID. You must own the process or be a privileged user. See also Section 7.8, "Job
Control".

Options
-signal
The signal number (from ps -f) or name (from kill -l). With a signal number of 9, the kill cannot be caught. The default is
TERM.
--

Consider all subsequent strings to be arguments, not options.
-l
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List the signal names. (Used by itself.)
-s signal

Specify signal. May be a name.

let let expressions
Perform arithmetic as specified by one or more integer expressions. expressions consist of numbers, operators, and shell
variables (which don't need a preceding $). Expressions must be quoted if they contain spaces or other special characters. For
more information and examples, see Section 7.5, "Arithmetic Expressions" earlier in this chapter. See also expr in Chapter 3,

"Linux Commands".

Examples
Both of the following examples add 1 to variable i:
let i= i+ 1 let "i = i + 1"

local local [options] [variable[= value]] [variable2[= value]] ...
Without arguments, print all local variables. Otherwise, create (and set, if specified) one or more local variables. See the declare
built-in command for options.

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logout logout [status]
Exit the shell, returning status as exit status to invoking program if specified. Can be used only in a login shell. Otherwise, use
exit.

popd popd [options]
Manipulate the directory stack. By default, remove the top directory and cd to it.
Options
+n
Remove the nth directory in the stack, counting from 0.
-n
Remove nth entry from the bottom of the stack, counting from 0.

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printf printf string [arguments]
Format a string like the C library printf function. Standard percent-sign formats are recognized in string, such as %i for integer.
Escape sequences such as \n can be included in string and are automatically recognized; if you want to include them in
arguments, specify a string of %b. You can escape characters in arguments to output a string suitable for input to other
commands by specifying a string of %q.

Examples
$ printf "Previous command: %i\ n" "$(($ HISTCMD-1))"Previous command: 534 $echo $PAGERless -E $printf "% q\ n" "\ t$ PAGER"\\ tless\ -E

The last command probably would be used to record a setting in a file where it could be read and assigned by another shell script.

pushd pushd directory
pushd [options]
By default, switch top two directories on stack. If specified, add a new directory to the top of the stack instead, and cd to it.
Options
+n
Rotate the stack to place the nth (counting from 0) directory at the top.
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-n
Rotate the stack to place the nth directory from the bottom of the stack at the top.

pwd pwd [-P]
Display the current working directory's absolute pathname. By default, any symbolic directories used when reaching the current
directory are displayed, but with the -P option the real names are displayed instead.

read read [options] variable1 [variable2 ...]
Read one line of standard input, and assign each word (as defined by IFS) to the corresponding variable, with all leftover words
assigned to the last variable. If only one variable is specified, the entire line will be assigned to that variable. The return status is
0 unless EOF is reached, a distinction that is useful for running loops over input files. If no variable names are provided, read the
entire string into the environment variable REPLY.

Options
-a var
Read each word into an element of var, which is treated as an array variable.
-d char
Stop reading the line at char instead of at the newline.
-e

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Line editing and command history are enabled during input.
-n num
Read only num characters from the line.
-p string
Display the prompt string to the user before reading each line, if input is interactive.
-r
Raw mode; ignore \ as a line continuation character.
-s
Do not echo the characters entered by the user (useful for reading a password).
-t seconds
Time out and return without setting any variables if input is interactive and no input has been entered for seconds seconds.
Examples
$ read first last addressSarah Caldwell 123 Main Street $echo "$ last, $first\ n$ address"Caldwell, Sarah 123 Main Street

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The following commands, which read a password into the variable $user_ pw and then display its value, use recently added
options that are not in all versions of bash in current use.

$ read -sp "Enter password (will not appear on screen)" user_ pwEnter password (will not appear on screen) $echo $user_ pwYou weren't supposed to know!

The following script reads input from the system's password file, which uses colons to delimit fields (making it a popular subject
for examples of input parsing).

IFS=: cat /etc/ passwd | while read account pw user group gecos home shell do echo "Account name $account has user info: $gecos" done

readonly readonly [options] [variable1 variable2 ...]
Prevent the specified shell variables from being assigned new values. Variables can be accessed (read) but not overwritten. In
bash, the syntax variable= value can be used to assign a new value that cannot be changed.

Options
-a
Treat the following names as array variables.
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-f
Treat the following names as functions, and set them read-only so that they cannot be changed.
-p
Display all read-only variables (default).

return return [n]
Used inside a function definition. Exit the function with status n or with the exit status of the previously executed command.

select select name [ in wordlist ; ]
do
commands
done
Choose a value for name by displaying the words in wordlist to the user and prompting for a choice. Store user input in the
variable REPLY and the chosen word in name. Then execute commands repeatedly until they execute a break or return. Default
prompt can be changed by setting the PS3 shell variable.

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set set [options] [arg1 arg2 ...]
With no arguments, set prints the values of all variables known to the current shell. Options can be enabled (-option) or disabled
(+ option). Options also can be set when the shell is invoked, via bash. Arguments are assigned in order to $1, $2, and so on.

Options
-Turn
off -v and -x, and turn off option processing.
--
Used as the last option; --turns off option processing so that arguments beginning with -are not misinterpreted as options.
(For example, you can set $1 to -1.) If no arguments are given after --, unset the positional parameters.

-a
From now on, automatically mark variables for export after defining or changing them.
-b
Report background job status at termination, instead of waiting for next shell prompt.
-e
Exit if a command yields a nonzero exit status.
-f
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Do not expand filename metacharacters (e. g., * ? [ ]). Wildcard expansion is sometimes called globbing.
-h
Locate commands as they are defined, and remember them.
-k
Assignment of environment variables (var= value) will take effect regardless of where they appear on the command line.
Normally, assignments must precede the command name.

-m
Monitor mode. Enable job control; background jobs executes in a separate process group. -m usually is set automatically.
-n
Read commands, but don't execute. Useful for checking errors, particularly for shell scripts.
-o [m]
List shell modes, or turn on mode m. Many modes can be set by other options. The modes can be turned off through the
+o option. Modes are:

allexport
Same as -a.
braceexpand

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Same as -B.
emacs
Enter Emacs editing mode (on by default).
errexit
Same as -e.
hashall
Same as -h.
histexpand
Same as -H.
history
Default. Preserve command history.
ignoreeof
Don't allow use of a single Ctrl-D (the end-of-file or EOF character) to log off; use the exit command to log off.
This has the same effect as setting the shell variable IGNOREEOF= 1.

interactive-comments
Treat all words beginning with #, and all subsequent words, as comments.
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keyword
Same as -k.
monitor
Same as -m.
noclobber
Same as -C.
noexec
Same as -n.
noglob
Same as -f.
notify
Same as -b.
nounset
Same as -u.
onecmd
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Same as -t.
physical
Same as -P.
posix
Match POSIX standard.
privileged
Same as -p.
verbose
Same as -v.
vi
Enable vi-style command-line editing.
xtrace
Same as -x.
+o [m]
Display modes or turn off mode m. See the -o option for a list of modes.
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-p
Start up as a privileged user; don't process $HOME/. profile.
-t
Exit after one command is executed.
-u
Indicate an error when user tries to use a variable that is undefined.
-v
Show each shell command line when read.
-x
Show commands and arguments when executed, preceded by a + or the prompt defined by the PS4 shell variable. This
provides step-by-step debugging of shell scripts. (Same as -o xtrace.)

-B
Default. Enable brace expansion.
-C
Don't allow output redirection (>) to overwrite an existing file.
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Default. Enable ! and !! commands.
-P
Print absolute pathnames in response to pwd. By default, bash includes symbolic links in its response to pwd.
Examples
set --"$ num" -20 -30 Set $1 to $num, $2 to -20, $3 to -30set -vx Read each command line; show it; execute it; show it again (with arguments)set +x Stop command tracingset -o noclobber Prevent file overwritingset +o noclobber Allow file overwriting again

shift shift [n]
Shift positional arguments (e. g., $2 becomes $1). If n is given, shift to the left n places.

source source file [arguments]
Read and execute lines in file. file does not have to be executable but must reside in a directory searched by PATH.

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suspend suspend [-f]
Same as Ctrl-Z. Often used to stop an su command.
Option
-f
Force suspend, even if shell is a login shell.

test test condition
or
[ condition ]
Evaluate a condition and, if its value is true, return a zero exit status; otherwise, return a nonzero exit status. An alternate form of
the command uses [] rather than the word test. condition is constructed using the following expressions. Conditions are true if the
description holds true.

File conditions
-a file
file exists.
-b file
file is a block special file.
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-c file
file is a character special file.
-d file
file is a directory.
-e file
file exists.
-f file
file is a regular file.
-g file
file has the set-group-ID bit set.
-h file
file is a symbolic link.
-k file
file has its sticky bit (no longer used) set.
-p file
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file is a named pipe (FIFO).
-r file
file is readable.
-s file
file has a size greater than 0.
-t [n]
The open file descriptor n is associated with a terminal device; default n is 1.
-u file
file has its set-user-ID bit set.
-w file
file is writable.
-x file
file is executable.
-G file
file's group is the process's effective group ID.
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-L file
file is a symbolic link.
-N file
file has been modified since its last time of access.
-O file
file's owner is the process's effective user ID.
-S file
file is a socket.
f1 -ef f2
Files f1 and f2 are linked (refer to same file through a hard link).
f1 -nt f2
File f1 is newer than f2.
f1 -ot f2
File f1 is older than f2.
String conditions
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-n s1
String s1 has nonzero length.
-o s1
Shell option s1 is set. Shell options are described under the set built-in command.
-z s1
String s1 has 0 length.
s1 = s2
Strings s1 and s2 are identical.
s1 == s2
Strings s1 and s2 are identical.
s1 != s2
Strings s1 and s2 are not identical.
s1 < s2
String s1 is lower in the alphabet (or other sort in use) than s2. By default, the check is performed character-by-character
against the ASCII character set.

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String s1 is higher in the alphabet (or other sort in use) than s2.
string
string is not null.
Integer comparisons
n1 -eq n2
n1 equals n2.
n1 -ge n2
n1 is greater than or equal to n2.
n1 -gt n2
n1 is greater than n2.
n1 -le n2
n1 is less than or equal to n2.
n1 -lt n2
n1 is less than n2.
n1 -ne n2
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n1 does not equal n2.
Combined forms
! condition
True if condition is false.
condition1 -a condition2
True if both conditions are true.
condition1 -o condition2
True if either condition is true.
Examples
Each of the following examples shows the first line of various statements that might use a test condition:
while test $# -gt 0 While there are arguments . . .while [ -n "$ 1" ] While the first argument is nonempty . . .if [ $count -lt 10 ] If $count is less than 10 . . .if [ -d RCS ] If the RCS directory exists . . .if [ "$ answer" != "y" ] If the answer is not y . . .if [ ! -r "$ 1" -o ! -f "$ 1" ] If the first argument is not a readable file or a regular file . . .

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times times
Print accumulated process times for user and system.

trap trap [-l] [ [commands] signals]
Execute commands if any of signals is received. Common signals include 0, 1, 2, and 15. Multiple commands should be quoted
as a group and separated by semicolons internally. If commands is the null string (i. e., trap "" signals), then signals will be
ignored by the shell. If commands is omitted entirely, reset processing of specified signals to the default action. If both
commands and signals are omitted, list current trap assignments. See examples at the end of this entry and under exec.

Option
-l
List signals.
Signals
Signals are listed along with what triggers them.
0
Exit from shell (usually when shell script finishes).
1
Hang up (usually logout).
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2
Interrupt (usually through Ctrl-C).
3
Quit.
4
Illegal instruction.
5
Trace trap.
6
Abort.
7
Unused.
8
Floating-point exception.
9

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Termination.
10
User-defined.
11
Reference to invalid memory.
12
User-defined.
13
Write to a pipe without a process to read it.
14
Alarm timeout.
15
Software termination (usually via kill).
16
Unused.

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17
Termination of child process.
18
Continue (if stopped).
19
Stop process.
20
Process suspended (usually through Ctrl-Z).
21
Background process has tty input.
22
Background process has tty output.
23
Unused.
24

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Unused.
25
Unused.
26
Unused.
27
Unused.
28
Unused.
29
I/ O possible on a channel.
Examples
trap "" 2 Ignore signal 2 (interrupts)trap 2 Obey interrupts again

Remove a $tmp file when the shell program exits or if the user logs out, presses Ctrl-C, or does a kill:
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type type [options] commands
Report absolute pathname of programs invoked for commands and whether or not they are hashed.
--
Consider all subsequent strings to be arguments, not options.
-a, -all
Print all occurrences of command, not just that which would be invoked.
-p, -path
Print the hashed value of command, which may differ from the first appearance of command in the PATH.
-t, -type
Determine and state if command is an alias, keyword, function, built-in, or file.
Example
$ type mv readmv is /bin/ mv read is a shell built-in

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typeset typeset
See declare.

ulimit ulimit [options] [n]
Print the value of one or more resource limits, or, if n is specified, set a resource limit to n. Resource limits can be either hard (-H)
or soft (-S). By default, ulimit sets both limits or prints the soft limit. The options determine which resource is acted on.

Options
--
Consider all subsequent strings to be arguments, not options.
-a
Print all current limits.
-H
Hard resource limit.
-S
Soft resource limit.
Specific limits
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These options limit specific resource sizes.
-c
Core files.
-d
Size of processes' data segments.
-f
Size of shell-created files.
-l
Size of memory that the process can lock.
-m
Resident set size.
-n
Number of file descriptors. On many systems, this cannot be set.
-p
Pipe size, measured in blocks of 512 bytes.

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-s
Stack size.
-t
Amount of CPU time, counted in seconds.
-u
Number of processes per user.
-v
Virtual memory used by shell.

umask umask [nnn]
umask [-p] [-S]
Display file creation mask or set file creation mask to octal value nnn. The file creation mask determines which permission bits
are turned off (e. g., umask 002 produces rw-rw-r--).

Options
-p
Display mask within an umask command so that a caller can read and execute it.

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-S
Display umask symbolically, rather than in octal.

unalias unalias [-a] names
Remove names from the alias list. See also alias.
Option
-a
Remove all aliases.

unset unset [options] names
Erase definitions of functions or variables listed in names.
Options
-f
Expect name to refer to a function.
-v
Expect name to refer to a variable (default).

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until until
test-commands
do
commands
done
Execute test-commands (usually a test or [ ] command), and if the exit status is nonzero (that is, the test fails), perform
commands; repeat.

wait wait [ID]
Pause in execution until all background jobs complete (exit status 0 will be returned), or pause until the specified background
process ID or job ID completes (exit status of ID is returned). Note that the shell variable $! contains the process ID of the most
recent background process. If job control is not in effect, ID can be only a process ID number. See Section 7.8, "Job Control".

Example
wait $! Wait for last background process to finish

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Built-in Commands (Linux in a Nutshell, 3rd Edition)
while while
test-commands
do
commands
done
Execute test-commands (usually a test or [] command) and if the exit status is 0, perform commands; repeat.

7.6. Command History 7.8. Job Control
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Job Control (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

7.8. Job Control
Job control lets you place foreground jobs in the background, bring background jobs to the
foreground, or suspend (temporarily stop) running jobs. Job control is enabled by default.
Once disabled, it can be reenabled by any of the following commands:

bash -m -i set -m set -o monitor

Many job control commands take jobID as an argument. This argument can be specified as
follows:

%n
Job number n
%s
Job whose command line starts with string s
%? s
Job whose command line contains string s
%%
Current job
%+
Current job (same as preceding)
%-file:///

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Job Control (Linux in a Nutshell, 3rd Edition)
Previous job
bash provides the following job control commands. For more information on these
commands, see Section 7.7, "Built-in Commands" earlier in this chapter.

bg
Put a job in the background.
fg

Put a job in the foreground.
jobs

List active jobs.
kill

Terminate a job.
stop

Suspend a background job.
stty tostop

Stop background jobs if they try to send output to the terminal.
wait

Wait for background jobs to finish.
Ctrl-Z

Suspend a foreground job. Then use bg or fg to restart it in the background or
foreground. (Your terminal may use something other than Ctrl-Z as the suspend
character.)

7.7. Built-in Commands 8. csh and tcsh
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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csh and tcsh (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

Chapter 8. csh and tcsh
Contents:
Overview of Features
Invoking the Shell
Syntax
Variables
Expressions
Command History
Command-Line Manipulation
Job Control
Built-in csh and tcsh Commands

This chapter describes the C shell and its enhancement, tcsh. On some versions of Linux, tcsh
is used as the C shell; in that case, the tcsh features described in this chapter work even when
you run csh. The C shell was so named because many of its programming constructs and
symbols resemble those of the C programming language.

The default shell on Linux systems is bash. If you want to use csh or tcsh, you first need to
change your default. Each user's shell preference is kept in the password table. If you are
creating an account, you can set the default shell when you add the user. If the account already
exists, use the chsh command to change the shell (see the command descriptions in Chapter 3,

"Linux Commands").

The following topics are presented in this chapter:
l Overview of features

l Invoking the shell
l Syntax

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csh and tcsh (Linux in a Nutshell, 3rd Edition)
l Variables

l Expressions
l Command history
l Command-line manipulation
l Job control
l Built-in commands

8.1. Overview of Features
Features of the C shell include:
l Input/ output redirection

l Wildcard characters (metacharacters) for filename abbreviation
l Shell variables for customizing your environment
l Integer arithmetic
l Access to previous commands (command history)
l Command-name abbreviation (aliasing)
l A built-in command set for writing shell programs
l Job control

The tcsh shell includes all of the C shell features. In addition, it includes the following
extensions to the C shell:

l Command-line editing and editor commands

l Word completion (tab completion)
l Spell checking
l Extended history commands

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csh and tcsh (Linux in a Nutshell, 3rd Edition)
l Extended handling of directory manipulation

l Scheduled events --such as logout or terminal locking after a set idle period and
delayed commands

l Additional shell built-ins

l Additional shell variables and environment variables
l New formatting sequences for the prompt string, as well as two new prompts (in loops
and spelling correction)

l Read-only variables

7.8. Job Control 8.2. Invoking the Shell
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Invoking the Shell (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
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8.2. Invoking the Shell
A shell command interpreter can be invoked as follows:

csh [options] [arguments]tcsh [options] [arguments]

csh and tcsh use syntax resembling C and execute commands from a terminal or a file.
Options -n, -v, and -x are useful when debugging scripts.

8.2.1. Options
-b
Allow the remaining command-line options to be interpreted as options to a specified
command, rather than as options to csh itself.
-c

Execute command specified following the argument.
-d

Load directory stack from ~/. cshdirs even if not a login shell. (tcsh)
-e

Exit if a command produces errors.
-f

Fast startup; start without executing .cshrc or .tcshrc.
-i

Invoke interactive shell (prompt for input).
-l

Login shell (must be the only option specified).
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-m

Load ~/. tcshrc even if effective user is not the owner of the file. (tcsh)
-n

Parse commands, but do not execute.
-s

Read commands from the standard input.
-t

Exit after executing one command.
-v

Display commands before executing them; expand history substitutions, but not other
substitutions (e. g., filename, variable, and command). Same as setting verbose.
-V

Same as -v, but also display .cshrc.
-x

Display commands before executing them, but expand all substitutions. Same as
setting echo.
-X

Same as -x, but also display .cshrc.

8.2.2. Arguments
Arguments are assigned, in order, to the positional parameters $1, $2, and so on. If the first
argument is an executable script, commands are read from it, and remaining arguments are
assigned to $1, $2, and so forth.

8. csh and tcsh 8.3. Syntax
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8.3. Syntax
This section describes the many symbols peculiar to csh and tcsh. The topics are arranged as follows:
l Special files
l Filename metacharacters
l Quoting
l Command forms
l Redirection forms

8.3.1. Special Files
Filename Description
~/. cshrc or ~/. tcshrc Executed at each instance of shell startup. For tcsh, if no ~/. tcshrc, uses ~/. cshrc if present.
~/. login Executed by login shell after .cshrc at login.
~/. cshdirs Executed by login shell after .login (tcsh).
~/. logout Executed by login shell at logout.
/etc/ passwd Source of home directories for ~name abbreviations.

8.3.2. Filename Metacharacters
Characters Meaning
* Match any string of 0 or more characters.
? Match any single character.
[abc...] Match any one of the enclosed characters; a hyphen can be used to specify a range (e. g., a-z, A-Z, 0-9).
{abc, xxx,...} Expand each comma-separated string inside braces.
~ Home directory for the current user.
~name Home directory of user name.

8.3.2.1. Examples
% ls new* Match new and new. 1 %cat ch? Match ch9 but not ch10 %vi [D-R]* Match files that begin with uppercase D through R %ls {ch, app}? Expand, then match ch1, ch2, app1, app2 %cd ~tom Change to tom's home directory

8.3.3. Quoting
Quoting disables a character's special meaning and allows it to be used literally, as itself. The following characters have special
meaning to the C shell:

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Syntax (Linux in a Nutshell, 3rd Edition)
Characters Description
; Command separator
& Background execution
( ) Command grouping
| Pipe
* ? [ ] ~ Filename metacharacters
{ } String expansion characters (usually don't require quoting)
> < & ! Redirection symbols
! ^ History substitution, quick substitution
" ' \ Used in quoting other characters
` Command substitution
$ Variable substitution
newline space tab Word separators

The characters that follow can be used for quoting:
" "Everything between " and " is taken literally, except for the following characters, which keep their special meaning:
$Variable substitution will occur.
`Command substitution will occur.
"This marks the end of the double quote.
\Escape next character.
!The history character.
newline
The newline character.
' 'Everything between ' and ' is taken literally except for ! (history) and another ', and newline.
\The character following a \ is taken literally. Use within " " to escape ", $, and `. Often used to escape itself, spaces, or
newlines. Always needed to escape a history character (usually !).

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8.3.3.1. Examples

% echo 'Single quotes "protect" double quotes'Single quotes "protect" double quotes

% echo "Well, isn't that "\"" special?"\"Well, isn't that "special"?

% echo "You have `ls| wc -l` files in `pwd`"You have 43 files in /home/ bob

% echo The value of \$ x is $xThe value of $x is 100

8.3.4. Command Forms

Command Action
cmd & Execute cmd in background.
cmd1 ; cmd2 Command sequence; execute multiple cmds on the same line.
(cmd1 ; cmd2) Subshell; treat cmd1 and cmd2 as a command group.
cmd1 | cmd2 Pipe; use output from cmd1 as input to cmd2.
cmd1 `cmd2` Command substitution; run cmd2 first and use its output as arguments to cmd1.
cmd1 || cmd2 OR; execute either cmd1 or (if cmd1 fails) cmd2.
cmd1 && cmd2 AND; execute cmd1 and then (if cmd1 succeeds) cmd2.

8.3.4.1. Examples
% nroff file > output & Format in the background %cd; ls Execute sequentially %(date; who; pwd) > logfile All output is redirected %sort file | pr -3 | lp Sort file, page output, then print %vi `grep -l ifdef *. c` Edit files found by grep %egrep '( yes| no) ' `cat list` Specify a list of files to search %grep XX file && lp file Print file if it contains the pattern %grep XX file || echo XX not found Echo an error message if XX not found

8.3.5. Redirection Forms

File Descriptor Name Common Abbreviation Typical Default

0 Standard input stdin Keyboard
1 Standard output stdout Screen
2 Standard error stderr Screen

The usual input source or output destination can be changed with redirection commands listed in the following sections.
8.3.5.1. Simple redirection

Command Action
cmd > file Send output of cmd to file (overwrite).

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cmd >! file Same as preceding, even if noclobber is set.
cmd >> file Send output of cmd to file (append).
cmd>>! file Same as preceding, even if noclobber is set.
cmd < file Take input for cmd from file.

cmd << text
Read standard input up to a line identical to text (text can be stored in a shell variable). Input usually is typed on the
screen or in the shell program. Commands that typically use this syntax include cat, echo, ex, and sed. If text is
enclosed in quotes, standard input will not undergo variable substitution, command substitution, etc.

8.3.5.2. Multiple redirection
Command Action
cmd >& file Send both standard output and standard error to file.
cmd >&! file Same as preceding, even if noclobber is set.
cmd >>& file Append standard output and standard error to end of file.
cmd >>&! file Same as preceding, even if noclobber is set.
cmd1 |& cmd2 Pipe standard error together with standard output.
(cmd> f1) >& f2 Send standard output to file f1 and standard error to file f2.

cmd | tee files Send output of cmd to standard output (usually the screen) and to files. (See the example in Chapter 3, "Linux Commands" under tee.)

8.3.5.3. Examples
% cat part1 > book Copy part1 to book %cat part2 part3 >> book Append parts 2 and 3 to same file as part1 %mail tim < report Take input to message from report %cc calc. c >& error_ out Store all messages, including errors %cc newcalc. c >&! error_ out Overwrite old file %grep Unix ch* |& pr Pipe all messages, including errors %(find / -print > filelist) >& no_ access Separate error messages from list of files %sed 's/^/ XX /' << "END_ ARCHIVE" Supply text right after commandThis is often how a shell archive is "wrapped", bundling text for distribution. You would normally run sed from a shell program, not from the command line. "END_ ARCHIVE"

8.2. Invoking the Shell 8.4. Variables
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8.4. Variables
This subsection describes the following:
l Variable substitution

l Variable modifiers
l Predefined shell variables
l Formatting for the prompt variable
l Sample .cshrc file
l Environment variables

8.4.1. Variable Substitution
In the following substitutions, braces ({}) are optional, except when needed to separate a variable name
from following characters that would otherwise be considered part of the name:

Variable Description
${ var} The value of variable var.

${ var[ i]}
Select word or words in position i of var. i can be a single number, a range m-n,a range -n (missing m implies 1), a range m-(missing n implies all
remaining words), or * (select all words). i also can be a variable that expands
to one of these values.

${# var} The number of words in var.
${# argv} The number of arguments.
$0 Name of the program.

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${ argv[ n]}
Individual arguments on command line (positional parameters); 1 n

9.
${ n} Same as ${ argv[ n]}.
${ argv[*]} All arguments on command line.
$* Same as {$ argv[*]}. $argv[$# argv]The last argument.
${? var} Return 1 if var is set, 0 if var is not set.

$$ Process number of current shell; useful as part of a filename for creating temporary files with unique names.
${? name} Return 1 if name is set, 0 if not.
$? 0 Return 1 if input filename is known, 0 if not.

8.4.1.1. Examples
Sort the third through last arguments and save the output in a file whose name is unique to this
process:

sort $argv[ 3-] > tmp.$$Process .cshrc commands only if the shell is interactive (i. e., the prompt variable must be set):
if ($? prompt) thenset commands, alias commands, etc.endif

8.4.2. Variable Modifiers
Except for $? var, $$, and $? 0, the variable substitutions in the preceding section may be followed by
one of these modifiers (when braces are used, the modifier goes inside them):

:rReturn the variable's root (the portion before the last dot).
:e

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Return the variable's extension.

:hReturn the variable's header (the directory portion).
:tReturn the variable's tail (the portion after the last slash).
:grReturn all roots.
:geReturn all extensions.
:ghReturn all headers.
:gtReturn all tails.
:qQuote a wordlist variable, keeping the items separate. Useful when the variable contains
filename metacharacters that should not be expanded.

:xQuote a pattern, expanding it into a wordlist.

8.4.2.1. Examples using pathname modifiers
The following table shows the use of pathname modifiers on the following variable:
set aa=(/ progs/ num. c /book/ chap. ps)

Variable Portion Specification Output Result
Normal variable echo $aa /progs/ num. c /book/ chap. ps
Second root echo $aa[ 2]: r /book/ chap

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Second header echo $aa[ 2]: h /book
Second tail echo $aa[ 2]: t chap. ps
Second extension echo $aa[ 2]: e ps
Root echo $aa: r /progs/ num /book/ chap. ps
Global root echo $aa: gr /progs/ num /book/ chap
Header echo $aa: h /progs /book/ chap. ps
Global header echo $aa: gh /progs /book
Tail echo $aa: t num. c /book/ chap. ps
Global tail echo $aa: gt num. c chap. ps
Extension echo $aa: e c /book/ chap. ps
Global extension echo $aa: ge c ps

8.4.2.2. Examples using quoting modifiers
Unless quoted, the shell expands variables to represent files in the current directory:
% set a="[ a-z]*" A="[ A-Z]*"% echo "$ a" "$ A"[a-z]* [A-Z]*

% echo $a $Aat cc m4 Book Doc

% echo $a: x $A[a-z]* Book Doc

% set d=($ a: q $A: q)% echo $dat cc m4 Book Doc

% echo $d: q[a-z]* [A-Z]*

% echo $d[ 1] +++ $d[ 2]at cc m4 +++ Book Doc

% echo $d[ 1]: q[a-z]*

8.4.3. Predefined Shell Variables
Variables can be set in one of two ways, by assigning a value:
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set var= valueor by simply turning the variable on:
set varIn the following list, variables that accept values are shown with the equals sign followed by the type
of value they accept; the value then is described. (Note, however, that variables such as argv, cwd, or
status are never explicitly assigned.) For variables that are turned on or off, the table describes what
they do when set. tcsh automatically sets (and, in some cases, updates) the variables addsuffix, argv,
autologout, cwd, dirstack, echo-style, edit, gid, home, loginsh, logout, oid, owd, path, prompt,
prompt2, prompt3, shell, shlvl, status, tcsh, term, tty, uid, user, and version. Variables in italics
are specific to tcsh.

Variable Description

addsuffix
Append / to directories and a space to files
during tab completion to indicate a precise
match.

ampm Display all times in 12-hour format.

argv=( args)
List of arguments passed to current
command; default is ().

autocorrect
Check spelling before attempting to
complete commands.

autoexpand
Expand history (such as ! references) during
command completion.

autolist[= ambiguous]
Print possible completions when correct one
is ambiguous. If ambiguous is specified,
print possible completions only when
completion adds no new characters.

autologout= logout-minutes [locking-minutes]
Log out after logout-minutes of idle time.
Lock the terminal after locking-minutes of
idle time, requiring a password before
continuing. Not used if the DISPLAY
environment variable is set.

backslash_ quote Always allow backslashes to quote \, ', and <">.
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cdpath= dirs
List of alternate directories to search when
locating arguments for cd, popd, or pushd.

color
Turn on color for ls-F, ls, or both. Setting to
nothing is equivalent to setting for both.

command
If set, holds the command passed to the
shell with the -c option.

complete= enhance
When enhance, ignore case in completion,
treat ., -, and _ as word separators, and
consider _ and -to be the same.

correct={ cmd| complete| all}
When cmd, spellcheck commands. When
complete, complete commands. When all,
spellcheck whole command line.

cwd= dir Full pathname of current directory.

dextract
When set, the pushd command extracts the
desired directory and puts it at the top of the
stack, instead of rotating the stack.

dirsfile= file
History file consulted by dirs -S and dirs -L.
Default is ~/. cshdirs.

dirstack
Directory stack, in array format.
dirstack[ 0] is always equivalent to cwd.
The other elements can be artificially
changed.

dspmbyte= code
Enable use of multibyte code; for use with
Kanji. See the tcsh manpage for details.

dunique
Make sure that each directory exists only
once in the stack.

echo
Redisplay each command line before
execution; same as csh -x command.

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echo_ style={ bsd| sysv| both| none}
Don't echo a newline with -n option (bsd) |
parse escaped characters (sysv) | do both |
do neither.

edit Enable command-line editor.
ellipsis
For use with prompt variable. Represent
skipped directories with ....

fignore= chars
List of filename suffixes to ignore during
filename completion (see filec).

filec
If set, a filename that is partially typed on
the command line can be expanded to its
full name when Esc is pressed. If more than
one filename would match, type EOF to list
possible completions. Ignored in tcsh.

gid User's group ID.
group User's group name.

histchars= ab
A two-character string that sets the
characters to use in history-substitution and
quick-substitution (default is !^).

histdup={ all| prev}
Maintain a record only of unique history
events (all), or do not enter new event when
it is the same as the previous one (prev).

histfile= file
History file consulted by history -S and
history -L. Default is ~/. history.

histlit
Do not expand history lines when recalling
them.

history= n format
The first word indicates the number of
commands to save in the history list. The
second indicates the format with which to
display that list (tcsh only; see the prompt
section for possible formats).

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home= dir
Home directory of user, initialized from
HOME. The ~ character is shorthand for
this value.

ignoreeof
Ignore an end-of-file (EOF) from terminals;
prevents accidental logout.

implicitcd
If directory name is entered as a command,
cd to that directory. Can be set to verbose
to echo the cd to standard output.

inputmode={ insert| overwrite} Control editor's mode.

listflags= flags
One or more of the x, a, or A options for the
ls-F built-in command. Second word can be
set to path for ls command.

listjobs= long
When a job is suspended, list all jobs (in
long format, if specified).

listlinks
In ls -F command, include type of file to
which links point.

listmax= num
Do not allow list-choices to print more than
num choices before prompting.

listmaxrows= num
Do not allow list-choices to print more than
num rows of choices before prompting.

loginsh Set if shell is a login shell.
logout Indicates status of an imminent logout (normal, automatic, or hangup).

mail=( n files)
One or more files checked for new mail
every 5 minutes or (if n is supplied) every n
seconds.

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matchbeep={ never| nomatch| ambiguous| notunique}
Specifies circumstances under which
completion should beep: never, if no match
exists, if multiple matches exist, or if
multiple matches exist and one is exact.

nobeep Disable beeping.
noclobber
Don't redirect output to an existing file;
prevents accidental destruction of files.

noglob
Turn off filename expansion; useful in shell
scripts.

nokanji Disable Kanji (if supported).

nonomatch
Treat filename metacharacters as literal
characters, if no match exists (e. g., vi ch*
creates new file ch* instead of printing "No
match").

nostat= directory-list Do not stat directory-list during completion.
notify Declare job completions when they occur.
owd Old working directory.

path=( dirs)
List of pathnames in which to search for
commands to execute. Initialized from
PATH; the default is: . /usr/ ucb /usr/ bin

printexitvalue Print all nonzero exit values.

prompt= 'str'String that prompts for interactive input;
default is %. See Section 8.4.4, "Formatting

for the Prompt Variable" later in this
chapter for formatting information.

prompt2= 'str'String that prompts for interactive input in
foreach and while loops and continued
lines (those with escaped newlines). See
Section 8.4.4, "Formatting for the Prompt

Variable" for formatting information.

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prompt3= 'str'String that prompts for interactive input in
automatic spelling correction. See Section

8.4.4, "Formatting for the Prompt Variable"
for formatting information.

promptchars= cc
Use the two characters specified as cc with
the %# prompt sequence to indicate
normal users and the superuser,
respectively.

pushdsilent
Do not print directory stack when pushd
and popd are invoked.

pushdtohome
Change to home directory when pushd is
invoked without arguments.

recexact
Consider completion to be concluded on
first exact match.

recognize_ only_ executables
When command completion is invoked,
print only executable files.

rmstar Prompt before executing the command rm *.

rprompt= string
The string to print on the right side of the
screen while the prompt is displayed on the
left. Specify as for prompt.

savedirs Execute dirs -S before exiting.

savehist= max [merge]
Execute history -S before exiting. Save no
more than max lines of history. If specified,
merge those lines with previous history
saves, and sort by time.

sched= string
Format for sched's printing of events. See
Section 8.4.4, "Formatting for the Prompt

Variable" for formatting information.

shell= file
Pathname of the shell program currently in
use; default is /bin/ csh.

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shlvl Number of nested shells.

status= n
Exit status of last command. Built-in
commands return 0 (success) or 1 (failure).

symlinks= {chase| ignore| expand}
Specify manner in which to deal with
symbolic links. Expand them to real
directory name in cwd (chase), treat them as
real directories (ignore), or expand
arguments that resemble pathnames
(expand).

tcsh Version of tcsh.
term Terminal type.

time= 'n %c'
If command execution takes more than n
CPU seconds, report user time, system time,
elapsed time, and CPU percentage. Supply
optional %c flags to show other data.

tperiod
Number of minutes between executions of
periodic alias.

tty Name of tty, if applicable.
uid User ID.
user Username.

verbose
Display a command after history
substitution; same as the command csh -v.

version
Shell's version and additional information,
including options set at compile time.

visiblebell Flash screen instead of beeping.

watch=([ n] user terminal...)
Watch for user logging in at terminal,
where terminal can be a tty name or any.
Check every n minutes or 10 by default.

who= string Specify information to be printed by watch.

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wordchars= chars
List of all nonalphanumeric characters that
may be part of a word. Default is *?_-.[]~=.

8.4.4. Formatting for the Prompt Variable
tcsh provides a list of substitutions that can be used in formatting the prompt. (csh allows only plain-string
prompts and the ! history substitution shown in the following list.) The list of available
substitutions includes:

%%
Literal %
%/
The present working directory
%~
The present working directory, in ~ notation
%#
# for the superuser, > for others
%?
Previous command's exit status
%b
End boldfacing
%c[[ 0] n], %.[[ 0] n]
The last n (default 1) components of the present working directory; if 0 is specified, replace
removed components with /< skipped>

%d
Day of the week (e. g., Mon, Tue)
%h, %!, !
Number of current history event

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%l
Current tty
%m
First component of hostname
%n
Username
%p
Current time, with seconds (12-hour mode)
%s
End standout mode (reverse video)
%t, %@
Current time (12-hour format)
%u
End underlining
%w
Month (e. g., Jan, Feb)
%y
Year (e. g., 99, 00)
%B
Begin boldfacing
%C
Similar to %c, but uses full pathnames instead of ~ notation
%D

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Day of month (e. g., 09, 10)

%M
Fully qualified hostname
%P
Current time, with seconds (24-hour format)
%S
Begin standout mode (reverse video)
%T
Current time (24-hour format)
%U
Begin underlining
%W
Month (e. g., 09, 10)
%Y
Year (e. g., 1999, 2000)

8.4.5. Sample .cshrc File
# PREDEFINED VARIABLES set path=(~ ~/ bin /usr/ ucb /bin /usr/ bin . ) set mail=(/ usr/ mail/ tom)

if ($? prompt) then # settings for interactive use set echo set noclobber ignoreeof

set cdpath=(/ usr/ lib /usr/ spool/ uucp) # Now I can type cd macros # instead of cd /usr/ lib/ macros

set history= 100 set prompt= 'tom \!% ' # includes history number set time= 3

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# MY VARIABLES set man1="/ usr/ man/ man1" # lets me do cd $man1, ls $man1 set a="[ a-z]*" # lets me do vi $a set A="[ A-Z]*" # or grep string $A

# ALIASES alias c "clear; dirs" # use quotes to protect ; or | alias h "history| more" alias j jobs -l alias ls ls -sFC # redefine ls command alias del 'mv \!* ~/ tmp_ dir' # a safe alternative to rm endif

8.4.6. Environment Variables
The C shell maintains a set of environment variables, which are distinct from shell variables and aren't
really part of the C shell. Shell variables are meaningful only within the current shell, but environment
variables are exported automatically, making them available globally. For example, C-shell variables
are accessible only to a particular script in which they're defined, whereas environment variables can
be used by any shell scripts, mail utilities, or editors you might invoke.

Environment variables are assigned as follows:
setenv VAR valueBy convention, environment variable names are all uppercase. You can create your own environment
variables, or you can use the predefined environment variables that follow.

The following environment variables have corresponding C-shell variables. When either one changes,
the value is copied to the other (italics means the variable is specific to tcsh):

GROUP
User's group name; same as group.
HOME
Home directory; same as home.
PATH
Search path for commands; same as path.
SHLVL

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Number of nested shell levels; same as shlvl.

TERM
Terminal type; same as term.
USER
User's login name; same as user.
Other environment variables, which do not have corresponding shell variables, include the following
(italics means the variable is specific to tcsh):

COLUMNS
Number of columns on terminal.
DISPLAY
Identifies user's display for the X Window System. If set, the shell doesn't set autologout.
EDITOR
Pathname to default editor. See also VISUAL.
HOST
Name of machine.
HOSTTYPE
Type of machine. Obsolete; will be removed eventually.
HPATH
Colon-separated list of directories to search for documentation.
LANG
Preferred language. Used for native language support.
LC_ CTYPE
The locale, as it affects character handling. Used for native language support.
LINES

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Number of lines on the screen.

LOGNAME
Another name for the USER variable.
MACHTYPE
Type of machine.
MAIL
The file that holds mail. Used by mail programs. This is not the same as the C-shell mail
variable, which only checks for new mail.

NOREBIND
Printable characters not rebound. Used for native language support.
OSTYPE
Operating system.
PWD
The current directory; the value is copied from cwd.
REMOTEHOST
Machine name of remote host.
SHELL
Undefined by default; once initialized to shell, the two are identical.
TERMCAP
The file that holds the cursor-positioning codes for your terminal type. Default is /etc/ termcap.
VENDOR
The system vendor.
VISUAL
Pathname to default full-screen editor. See also EDITOR.

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Variables (Linux in a Nutshell, 3rd Edition)
8.3. Syntax 8.5. Expressions
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Edition

8.5. Expressions
Expressions are used in @, if, and while statements to perform arithmetic, string comparisons,
file testing, and so on. exit and set also specify expressions, as can the tcsh built-in command
filetest. Expressions are formed by combining variables and constants with operators that
resemble those in the C programming language. Operator precedence is the same as in C but
can be remembered as follows:

1. * / %
2. + -Group

all other expressions inside parentheses. Parentheses are required if the expression
contains <, >, &, or |.

8.5.1. Operators
Operators can be one of the following types:

8.5.1.1. Assignment operators

Operator Description
= Assign value.
+= -= Reassign after addition/ subtraction.
*= /= %= Reassign after multiplication/ division/ remainder.
&= ^= |= Reassign after bitwise AND/ XOR/ OR.
++ Increment.
--Decrement.

8.5.1.2. Arithmetic operators
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Operator Description
* / % Multiplication; integer division; modulus (remainder)
+ -Addition; subtraction

8.5.1.3. Bitwise and logical operators
Operator Description
~ Binary inversion (one's complement).
! Logical negation.
<< >> Bitwise left shift; bitwise right shift.
& Bitwise AND.
^ Bitwise exclusive OR.
| Bitwise OR.
&& Logical AND.
|| Logical OR.

{ command }Return 1 if command is successful, 0 otherwise. Note that this is the
opposite of command's normal return code. The $status variable may be
more practical.

8.5.1.4. Comparison operators
Operator Description
== != Equality; inequality
<= >= Less than or equal to; greater than or equal to
< > Less than; greater than

8.5.1.5. File inquiry operators
Command substitution and filename expansion are performed on file before the test is
performed. tcsh permits operators to be combined (e. g., -ef). The following is a list of the
valid file inquiry operators:

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Operator Description
-d file The file is a directory.
-e file The file exists.
-f file The file is a plain file.
-o file The user owns the file.
-r file The user has read permission.
-w file The user has write permission.
-x file The user has execute permission.
-z file The file has 0 size.
! Reverse the sense of any preceding inquiry.

Some additional operators specific to tcsh are:
Operator Description
-b file The file is a block special file.
-c file The file is a character special file.
-g file The file's set-group-ID bit is set.
-k file The file's sticky bit is set.
-l file The file is a symbolic link.
-L file Apply any remaining operators to symbolic link, not the file it points to.
-p file The file is a named pipe (FIFO).
-s file The file has nonzero size.
-S file The file is a socket special file.
-t file file is a digit and is an open file descriptor for a terminal device.
-u file The file's set-user-ID bit is set.
-X file The file is executable and is in the path or is a shell built-in.

Finally, tcsh provides the following operators, which return other kinds of information:
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Operator Description
-A[:] file Last time file was accessed, as the number of seconds since the Epoch. With a colon (:), the result is in timestamp format.

-C[:] file Last time inode was modified. With a colon (:), the result is in timestamp format.
-D file Device number.
-F file Composite file identifier, in the form device: inode.

-G[:] file Numeric group ID for the file. With a colon (:), the result is the group name if known; otherwise, the numeric group ID.
-I file Inode number.
-L file The name of the file pointed to by symbolic link file.

-M[:] file Last time file was modified. With a colon (:), the result is in timestamp format.
-N file Number of hard links.
-P[:] file Permissions in octal, without leading 0. With a colon (:), the result includes a leading 0.

-Pmode[:] file Equivalent to -P file ANDed to mode. With a colon (:), the result includes a leading 0.
-U[:] file Numeric user ID of the file's owner. With a colon (:), the result is the username if known, otherwise the numeric user ID.
-Z file The file's size, in bytes.

8.5.2. Examples
The following examples show @ commands and assume n = 4:

Expression Value of $x
@ x = ($ n > 10 || $n < 5) 1
@ x = ($ n >= 0 && $n < 3) 0
@ x = ($ n << 2) 16

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@ x = ($ n >> 2) 1
@ x = $n % 2 0
@ x = $n % 3 1

The following examples show the first line of if or while statements:
Expression Meaning
while ($# argv != 0) While there are arguments . . .
if ($ today[ 1] == <"> Fri<">) If the first word is "Fri". . .
if (-f $argv[ 1]) If the first argument is a plain file. . .
if (! -d $tmpdir) If tmpdir is not a directory. . .

8.4. Variables 8.6. Command History
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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8.6. Command History
Previously executed commands are stored in a history list. The C shell lets you access this list
so you can verify commands, repeat them, or execute modified versions of them. The history
built-in command displays the history list; the predefined variables histchars and history also
affect the history mechanism. There are four ways to use the history list:

l Rerun a previous command

l Make command substitutions
l Make argument substitutions (replace specific words in a command)
l Extract or replace parts of a command or word

The following subsections describe the csh tools for editing and rerunning commands. If you
are running tcsh, you can use any of these features. In addition, you can use the arrow keys to
move around in the command line and then use the editing features described in Section 8.7.5,

"Command-Line Editing with tcsh" to modify the command. The tcsh arrow keys are:

Key Description
Up arrow Previous command.
Down arrow Next command.
Left arrow Move left in command line.
Right arrow Move right in command line.

8.6.1. Command Substitution
Command Description

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! Begin a history substitution.
!! Previous command.
!N Command number N in history list.
!-N Nth command back from current command.
!string Most recent command that starts with string.
!? string? Most recent command that contains string.
!? string?% Most recent command argument that contains string.
!$ Last argument of previous command.
!! string Previous command, then append string.
!N string Command N, then append string.
!{ s1} s2 Most recent command starting with string s1, then append string s2.

^old^ new^ Quick substitution; change string old to new in previous command; execute modified command.

8.6.2. Command Substitution Examples
The following command is assumed:
%3 vi cprogs/ 01. c ch002 ch03

Event Command Command
Number Typed Executed
4 ^00^ 0 vi cprogs/ 01. c ch02 ch035 nroff !* nroff cprogs/ 01. c ch02 ch036 nroff !$ nroff ch037 !vi vi cprogs/ 01. c ch02 ch038 !6 nroff ch039 !? 01 vi cprogs/ 01. c ch02 ch0310 !{ nr}. new nroff ch03. new

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11 !!| lp nroff ch03. new | lp12 more !? pr?% more cprogs/ 01. c

8.6.3. Word Substitution
Colons may precede any word specifier.

Specifier Description
:0 Command name
:n Argument number n
^ First argument
$ Last argument
:n-m Arguments n through m
-m Words 0 through m same as :0-m
:n-Arguments n through next-to-last
:n* Arguments n through last; same as n-$
* All arguments; same as ^-$ or 1-$
# Current command line up to this point; fairly useless

8.6.4. Word Substitution Examples
The following command is assumed:
%13 cat ch01 ch02 ch03 biblio back

Event Command Command
Number Typed Executed
14 ls !13^ ls ch0115 sort !13:* sort ch01 ch02 ch03 biblio back16 lp !cat: 3* more ch03 biblio back

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17 !cat: 0-3 cat ch01 ch02 ch0318 vi !-5: 4 vi biblio

8.6.5. History Modifiers
Command and word substitutions can be modified by one or more of the following modifiers:

8.6.5.1. Printing, substitution, and quoting

Modifier Description
:p Display command, but don't execute.
:s/ old/ new Substitute string new for old, first instance only.
:gs/ old/ new Substitute string new for old, all instances.
:& Repeat previous substitution (: s or ^ command), first instance only.
:g& Repeat previous substitution, all instances.
:q Quote a wordlist.
:x Quote separate words.

8.6.5.2. Truncation
Modifier Description
:r Extract the first available pathname root (the portion before the last period).
:gr Extract all pathname roots.
:e Extract the first available pathname extension (the portion after the last period).
:ge Extract all pathname extensions.
:h Extract the first available pathname header (the portion before the last slash).
:gh Extract all pathname headers.
:t Extract the first available pathname tail (the portion after the last slash).
:gt Extract all pathname tails.
:u Make first lowercase letter uppercase (tcsh only).

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:l Make first uppercase letter lowercase (tcsh only).

:a Apply modifier( s) following a as many times as possible to a word. If used with g, a is applied to all words (tcsh only).

8.6.6. History Modifier Examples
From the preceding, command number 17 is:
%17 cat ch01 ch02 ch03

Event Command Command
Number Typed Executed
19 !17: s/ ch/ CH/ cat CH01 ch02 ch0320 !17g& cat CH01 CH02 CH0321 !more: p more cprogs/ 01. c (displayed only)
22 cd !$: h cd cprogs23 vi !mo:$: t vi 01. c24 grep stdio !$ grep stdio 01. c25 ^stdio^ include stdio^: q grep <"> include stdio<"> 01. c26 nroff !21: t: p nroff 01. c (is that what I wanted?)
27 !! nroff 01. c (execute it)

8.6.7. Special Aliases in tcsh
Certain special aliases can be set in tcsh. The aliases are initially undefined. Once set, they are
executed when specific events occur. The following is a list of the special aliases:

beepcmd
At beep.
cwdcmd
When the current working directory changes.

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periodic

Every few minutes. The exact amount of time is set by the tperiod shell variable.
precmd
Before printing a new prompt.
shell shell
If a script does not specify a shell, interpret it with shell, which should be a full
pathname.

8.5. Expressions 8.7. Command-Line
Manipulation

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Command-Line Manipulation (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

8.7. Command-Line Manipulation
csh and tcsh offer a certain amount of functionality in manipulating the command line. Both
shells offer word or command completion, and tcsh allows you to edit a command line.

8.7.1. Completion
Both tcsh and csh provide word completion. tcsh automatically completes words and
commands when the Tab key is hit; csh does so only when the filec variable is set, after the
Esc key is hit. If the completion is ambiguous (i. e., more than one file matches the provided
string), the shell completes as much as possible and beeps to notify you that the completion is
not finished. You may request a list of possible completions with Ctrl-D. tcsh also notifies
you when a completion is finished by appending a space to complete filenames or commands
and a / to complete directories.

Both csh and tcsh recognize ~ notation for home directories. The shells assume that words at
the beginning of a line and subsequent to |, &, ;, ||, or && are commands and modify their
search paths appropriately. Completion can be done midword; only the letters to the left of the
prompt are checked for completion.

8.7.2. Related Shell Variables
l autolist

l fignore
l listmax
l listmaxrows

8.7.3. Related Command-Line Editor Commands
l complete-word-back

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l complete-word-forward

l expand-glob
l list-glob

8.7.4. Related Shell Built-ins
l complete

l uncomplete

8.7.5. Command-Line Editing with tcsh
tcsh lets you move your cursor around in the command line, editing the line as you type.
There are two main modes for editing the command line, based on the two most common text
editors: Emacs and vi. Emacs mode is the default; you can switch between the modes with:

bindkey -e Select Emacs bindings bindkey -v Select vi bindings

The main difference between the Emacs and vi bindings is that the Emacs bindings are
modeless (i. e., they always work). With the vi bindings, you must switch between insert and
command modes; different commands are useful in each mode. Additionally:

l Emacs mode is simpler; vi mode allows finer control.

l Emacs mode allows you to yank cut text and set a mark; vi mode does not.
l The command-history-searching capabilities differ.

8.7.5.1. Emacs mode
Table 8-1 through Table 8-3 describe the various editing keystrokes available in Emacs mode.

Table 8-1. Cursor Positioning Commands (Emacs Mode)

Command Description
Ctrl-B Move cursor back (left) one character.
Ctrl-F Move cursor forward (right) one character.

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Esc b Move cursor back one word.
Esc f Move cursor forward one word.
Ctrl-A Move cursor to beginning of line.
Ctrl-E Move cursor to end of line.

Table 8-2. Text Deletion Commands (Emacs Mode)
Command Description
Del or Ctrl-H Delete character to left of cursor.
Ctrl-D Delete character under cursor.
Esc d Delete word.
Esc Del or Esc Ctrl-H Delete word backward.
Ctrl-K Delete from cursor to end-of-line.
Ctrl-U Delete entire line.

Table 8-3. Command Control (Emacs Mode)
Command Description
Ctrl-P Previous command.
Ctrl-N Next command.
Up arrow Previous command.
Down arrow Next command.

cmd-fragment Esc p Search history for cmd-fragment, which must be the beginning of a command.
cmd-fragment Esc n Like Esc p, but search forward.
Esc num Repeat next command num times.
Ctrl-Y Yank previously deleted string.

8.7.5.2. vi mode

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vi mode has two submodes, insert mode and command mode. The default mode is insert. You
can toggle modes by pressing Esc; alternatively, in command mode, typing a (append) or i
(insert) will return you to insert mode.

Tables 8-4 through 8-10 describe the editing keystrokes available in vi mode.
Table 8-4. Commands Available (vi's Insert and Command Mode)

Command Description
Ctrl-P Previous command
Ctrl-N Next command
Up arrow Previous command
Down arrow Next command
Esc Toggle mode

Table 8-5. Editing Commands (vi Insert Mode)
Command Description
Ctrl-B Move cursor back (left) one character.
Ctrl-F Move cursor forward (right) one character.
Ctrl-A Move cursor to beginning of line.
Ctrl-E Move cursor to end-of-line.
DEL or Ctrl-H Delete character to left of cursor.
Ctrl-W Delete word backward.
Ctrl-U Delete from beginning of line to cursor.
Ctrl-K Delete from cursor to end-of-line.

Table 8-6. Cursor Positioning Commands (vi Command Mode)
Command Description
h or Ctrl-H Move cursor back (left) one character.
l or SPACE Move cursor forward (right) one character.

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w Move cursor forward (right) one word.
b Move cursor back (left) one word.
e Move cursor to next word ending.

W, B, E Like w, b, and e, but treat just whitespace as word separator instead of any non-alphanumeric character.
^ or Ctrl-A Move cursor to beginning of line (first nonwhitespace character).
0 Move cursor to beginning of line.
$ or Ctrl-E Move cursor to end-of-line.

Table 8-7. Text Insertion Commands (vi Command Mode)
Command Description
a Append new text after cursor until Esc.
i Insert new text before cursor until Esc.
A Append new text after end of line until Esc.
I Insert new text before beginning of line until Esc.

Table 8-8. Text Deletion Commands (vi Command Mode)
Command Description
x Delete character under cursor.
X or Del Delete character to left of cursor.
dm Delete from cursor to end of motion command m.
D Same as d$.
Ctrl-W Delete word backward.
Ctrl-U Delete from beginning of line to cursor.
Ctrl-K Delete from cursor to end of line.

Table 8-9. Text Replacement Commands (vi Command Mode)

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Command-Line Manipulation (Linux in a Nutshell, 3rd Edition)
Command Description
cm Change characters from cursor to end of motion command m until Esc.
C Same as c$.
rc Replace character under cursor with character c.
R Replace multiple characters until Esc.
s Substitute character under cursor with characters typed until Esc.

Table 8-10. Character-Seeking Motion Commands (vi Command Mode)
Command Description
fc Move cursor to next instance of c in line.
Fc Move cursor to previous instance of c in line.
tc Move cursor just before next instance of c in line.
Tc Move cursor just after previous instance of c in line.
; Repeat previous f or F command.
, Repeat previous f or F command in opposite direction.

8.6. Command History 8.8. Job Control
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Job Control (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

8.8. Job Control
Job control lets you place foreground jobs in the background, bring background jobs to the
foreground, or suspend (temporarily stop) running jobs. The C shell provides the following
commands for job control. For more information on these commands, see Section 8.9, "Built-in

csh and tcsh Commands".

bg
Put a job in the background.
fg

Put a job in the foreground.
jobs

List active jobs.
kill

Terminate a job.
notify

Notify when a background job finishes.
stop

Suspend a background job.
Ctrl-Z

Suspend the foreground job.
Many job control commands take jobID as an argument. This argument can be specified as
follows:

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Job Control (Linux in a Nutshell, 3rd Edition)
Job number n.
%s

Job whose command line starts with string s.
%? s

Job whose command line contains string s.
%%

Current job.
%

Current job (same as preceding).
%+

Current job (same as preceding).
%-Previous

job.

8.7. Command-Line
Manipulation
8.9. Built-in csh and tcsh
Commands

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Built-in csh and tcsh Commands (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

8.9. Built-in csh and tcsh Commands
@ @ [variable[ n]= expression]
Assign the value of the arithmetic expression to variable or to the nth element of variable if the index n is specified. With no
variable or expression specified, print the values of all shell variables (same as set). Expression operators as well as examples
are listed under Section 8.5, "Expressions" earlier in this chapter. Two special forms also are valid:

@ variable++
Increment variable by 1.
@ variable--

Decrement variable by 1.

# #
Ignore all text that follows on the same line. # is used in shell scripts as the comment character and is not really a command.

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#! #! shell
Used as the first line of a script to invoke the named shell (with optional arguments). Not supported in all shells. For example:
#!/ bin/ csh -f

: :
Null command. Returns an exit status of 0. The colon command often is put as the first character of a Bourne-or Korn-shell
script to act as a place-holder to keep a # (hash) from accidentally becoming the first character.

alias alias [name [command]]
Assign name as the shorthand name, or alias, for command. If command is omitted, print the alias for name; if name also is
omitted, print all aliases. Aliases can be defined on the command line, but more often they are stored in .cshrc so that they take
effect upon logging in. (See the sample .cshrc file earlier in this chapter.) Alias definitions can reference command-line
arguments, much like the history list. Use \!* to refer to all command-line arguments, \!^ for the first argument, \!\!: 2 for the
second, \!$ for the last, and so on. An alias name can be any valid Unix command; however, you lose the original command's
meaning unless you type \name. See also unalias and the "Special Aliases in tcsh" section.

Examples
Set the size for xterm windows under the X Window System:
alias R 'set noglob; eval `resize` unset noglob'Show aliases that contain the string ls:
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Run nroff on all command-line arguments:
alias ms 'nroff -ms \!* 'Copy the file that is named as the first argument:
alias back 'cp \!^ \!^. old'Use the regular ls, not its alias:
% \ls

alloc alloc
Print totals of used and free memory.

bg bg [jobIDs]
Put the current job or the jobIDs in the background.
Example
To place a time-consuming process in the background, you might begin with:
4% nroff -ms report Ctrl-Zand then issue any one of the following:
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5% bg5% bg % Current job 5%bg %1 Job number 1 5%bg %nr Match initial string nroff 5%% &

bindkey bindkey [options] [key] [command]
tcsh only. Display all key bindings, or bind a key to a command.
Options
-a
List standard and alternate key bindings.
-b key
Expect key to be one of the following: a control character (in hat notation --e. g., ^B --or C notation --e. g., C-B); a
metacharacter (e. g., M-B); a function key (e. g., F-string); or an extended prefix key (e. g., X-B).

-c command
Interpret command as a shell, not editor, command.
-d key
Bind key to its original binding.

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-e
Bind to standard Emacs bindings.
-k key
Expect key to refer to an arrow (left, right, up, or down).
-l
List and describe all editor commands.
-r key
Completely unbind key.
-s
Interpret command as a literal string and treat as terminal input.
-u
Print usage message.
-v
Bind to standard vi bindings.

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break break
Resume execution following the end command of the nearest enclosing while or foreach.

breaksw breaksw
Break from a switch; continue execution after the endsw.

built-ins built-ins
tcsh only. Print all built-in shell commands.

bye bye
tcsh only. Same as logout.

case case pattern :
Identify a pattern in a switch.

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cd cd [dir]
Change working directory to dir. Default is user's home directory. If dir is a relative pathname but is not in the current
directory, the cdpath variable is searched. See the sample .cshrc file earlier in this chapter. tcsh includes some options for cd:

tcsh options
-Change
to previous directory.
-l
Explicitly expand ~ notation.
-n
Wrap entries before end-of-line; implies -p.
-p
Print directory stack.
-v
Print entries one per line; implies -p.

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chdir chdir [dir]
Same as cd. Useful if you are redefining cd.

complete complete [string [word/ pattern/ list[: select]/[ suffix]]]
tcsh only. List all completions, or, if specified, all completions for string (which may be a pattern). Further options can be
specified.

Options for word
c
Complete current word only and without referring to pattern.
C
Complete current word only, referring to pattern.
n
Complete previous word.
N
Complete word before previous word.
p

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Expect pattern to be a range of numbers. Perform completion within that range.
Options for list
Various lists of strings can be searched for possible completions. Some list options include:
(string)
Members of the list string
$variable
Words from variable
`command`Output from command
a
Aliases
b
Bindings
c
Commands

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C
External (not built-in) commands
d
Directories
D
Directories whose names begin with string
e
Environment variables
f
Filenames
F
Filenames that begin with string
g
Groups
j

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Jobs
l
Limits
n
Nothing
s
Shell variables
S
Signals
t
Text files
T
Text files whose names begin with string
u
Users

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v
Any variables
x
Like n but prints select as an explanation with the editor command list-choices
X
Completions
select
select should be a glob pattern. Completions are limited to words that match this pattern. suffix is appended to all completions.

continue continue
Resume execution of nearest enclosing while or foreach.

default default :
Label the default case (typically last) in a switch.

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dirs dirs [options]
Print the directory stack, showing the current directory first. See also popd and pushd. All options except -l, -n, and -v are tcsh
extensions.

Options
-c
Clear the directory stack.
-l
Expand the home directory symbol (~) to the actual directory name.
-n
Wrap output.
-v
Print one directory per line.
-L file
Re-create stack from file, which should have been created by dirs -S file.
-S file
Print to file a series of pushd and popd commands, that can be invoked to replicate the stack.
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Built-in csh and tcsh Commands (Linux in a Nutshell, 3rd Edition)
echo echo [-n] string
Write string to standard output; if -n is specified, the output is not terminated by a newline. Unlike the Unix version (/ bin/ echo)
and the Bourne-shell version, the C shell's echo doesn't support escape characters. See also echo in Chapter 3, "Linux

Commands", and Chapter 7, "bash: The Bourne-Again Shell".

echotc echotc [options] arguments
tcsh only. Display terminal capabilities, or move cursor on screen, depending on the argument.
Options
-s
Return empty string, not error, if capability doesn't exist.
-v
Display verbose messages.
Arguments
baud
Display current baud.
cols
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Display current column.
cm column row
Move cursor to specified coordinates.
home
Move cursor to home position.
lines
Print number of lines per screen.
meta
Does this terminal have meta capacity (usually the Alt key)?
tabs
Does this terminal have tab capacity?

else else
Reserved word for interior of if ... endif statement.

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end end
Reserved word that ends a foreach or switch statement.

endif endif
Reserved word that ends an if statement.

endsw endsw
Reserved word that ends a switch statement.

eval eval args
Typically, eval is used in shell scripts, and args is a line of code that may contain shell variables. eval forces variable expansion
to happen first and then runs the resulting command. This "double scanning" is useful any time shell variables contain
input/ output redirection symbols, aliases, or other shell variables. (For example, redirection normally happens before variable
expansion, so a variable containing redirection symbols must be expanded first using eval; otherwise, the redirection symbols
remain uninterpreted.)

Examples
The following line can be placed in the .login file to set up terminal characteristics:
set noglob eval `tset -s xterm` unset noglobThe following commands show the effect of eval:
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% set b= '$ a'% set a= hello% echo $b Read the command line once $a %eval echo $b Read the command line twice hello

Another example of eval can be found under alias.

exec exec command
Execute command in place of current shell. This terminates the current shell, rather than create a new process under it.

exit exit [( expr)]
Exit a shell script with the status given by expr. A status of zero means success; nonzero means failure. If expr is not specified,
the exit value is that of the status variable. exit can be issued at the command line to close a window (log out).

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Built-in csh and tcsh Commands (Linux in a Nutshell, 3rd Edition)
fg fg [jobIDs]
Bring the current job or the jobIDs to the foreground. jobID can be %job-number.
Example
If you suspend a vi editing session (by pressing Ctrl-Z), you might resume vi using any of these commands:

% %% fg% fg %% fg %vi Match initial string

filetest filetest -op files
tcsh only. Apply op file-test operator to files. Print results in a list. See Section 8.5.1.5, "File inquiry operators" for the list of
file-test operators.

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foreach foreach name (wordlist)
commands
end
Assign variable name to each value in wordlist and execute commands between foreach and end. You can use foreach as a
multiline command issued at the C-shell prompt (first of the following examples), or you can use it in a shell script (second
example).

Examples
Rename all files that begin with a capital letter:
% foreach i ([ A-Z]*)? mv $i $i. new? end

Check whether each command-line argument is an option or not:
foreach arg ($ argv) # does it begin with -? if ("$ arg" =~ -*) then echo "Argument is an option" else echo "Argument is a filename" endif end

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glob glob wordlist
Do filename, variable, and history substitutions on wordlist. No \ escapes are recognized in its expansion, and words are
delimited by null characters. glob typically is used in shell scripts to hardcode a value so that it remains the same for the rest of
the script.

goto goto string
Skip to a line whose first nonblank character is string followed by a colon and continue execution below that line. On the goto
line, string can be a variable or filename pattern, but the label branched to must be a literal, expanded value and must not occur
within a foreach or while.

hashstat hashstat
Display statistics that show the hash table's level of success at locating commands via the path variable.

history history [options]
Display the list of history events. (History syntax is discussed earlier, in "Command History.")
Options
-c
tcsh only. Clear history list.
-h
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Print history list without event numbers.
-r
Print in reverse order; show oldest commands last.
n
Display only the last n history commands, instead of the number set by the history shell variable.
-L file
tcsh only. Load series of pushd and popd commands from file in order to re-create a saved stack.
-M file
tcsh only. Merge the current directory stack and the stack saved in file. Save both, sorted by time, in file, as a series of
pushd and popd commands.

-S file
tcsh only. Print to file a series of pushd and popd commands that can be invoked to replicate the stack.
Example
To save and execute the last five commands:
history -h 5 > do_ it source do_ it

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Built-in csh and tcsh Commands (Linux in a Nutshell, 3rd Edition)
hup hup [command]
tcsh only. Start command but make it exit when sent a hangup signal, which is sent when shell exits. By default, configure shell
script to exit on hangup signal.

if if
Begin a conditional statement. The simple format is:
if (expr) cmdThere are three other possible formats, shown side-by-side:
if (expr) then if (expr) then if (expr) thencmds cmds1 cmds1endif else else if (expr) thencmds2 cmds2endif elsecmds3endif

In the simplest form, execute cmd if expr is true; otherwise do nothing (redirection still occurs; this is a bug). In the other forms,
execute one or more commands. If expr is true, continue with the commands after then; if expr is false, branch to the
commands after else (or branch to after the else if and continue checking). For more examples, see Section 8.5, "Expressions"

earlier in this chapter, shift, or while.

Example
Take a default action if no command-line arguments are given:
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Built-in csh and tcsh Commands (Linux in a Nutshell, 3rd Edition)
if ($# argv == 0) then echo "No filename given. Sending to Report." set outfile = Report else set outfile = $argv[ 1] endif

jobs jobs [-l]
List all running or stopped jobs; -l includes process IDs. For example, you can check whether a long compilation or text format
is still running. Also useful before logging out.

kill kill [options] ID
Terminate each specified process ID or job ID. You must own the process or be a privileged user. This built-in is similar to
/bin/ kill described in Chapter 3, "Linux Commands" but also allows symbolic job names. Stubborn processes can be killed

using signal 9.

Options
-l
List the signal names. (Used by itself.)
-signal

The signal number or name, without the SIG prefix (e. g., HUP, not SIGHUP). The command kill -l prints a list of the
available signal names. The list varies by system architecture; for a PC-based system, it looks like this:

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HUP INT QUIT ILL TRAP ABRT BUS FPE KILL USR1 SEGV USR2 PIPE ALRM TERM STKFLT CHLD CONT STOP TSTP TTIN TTOU URG XCPU XFSZ VTALRM PROF WINCH POLL PWR UNUSED

The signals and their numbers are defined in /usr/ include/ asm/ signal. h; look in that file to find the signals that apply to
your system.

Examples
If you've issued the following command:
44% nroff -ms report &you can terminate it in any of the following ways:

45% kill 19536 Process ID 45%kill % Current job 45%kill %1 Job number 1 45%kill %nr Initial string 45%kill %? report Matching string

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limit limit [-h] [resource [limit]]
Display limits or set a limit on resources used by the current process and by each process it creates. If no limit is given, the
current limit is printed for resource. If resource also is omitted, all limits are printed. By default, the current limits are shown or
set; with -h, hard limits are used. A hard limit imposes an absolute limit that can't be exceeded. Only a privileged user may raise
it. See also unlimit.

Option
-h
Use hard, not current, limits.
Resource
cputime
Maximum number of seconds the CPU can spend; can be abbreviated as cpu.
filesize
Maximum size of any one file.
datasize
Maximum size of data (including stack).
stacksize
Maximum size of stack.
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coredumpsize
Maximum size of a core dump file.
Limit
A number followed by an optional character (a unit specifier).

For cputime: nh (for n hours)
nm (for n minutes)
mm: ss (minutes and seconds)
For others: nk (for n kilobytes, the default)
nm (for n megabytes)

log log
tcsh only. Consult the watch variable for list of users being watched. Print list of those who are presently logged in. If -is
entered as an option, reset environment as if user had logged in with new group.

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Built-in csh and tcsh Commands (Linux in a Nutshell, 3rd Edition)
logout logout
Terminate the login shell.

ls-F ls-F [options] [files]
tcsh only. Faster alternative to ls -F. If given any options, invokes ls.

newgrp newgrp [-] [group]
tcsh only. Change user's group ID to specified group ID, or, if none is specified, to original group ID. If -is entered as an
option, reset environment as if user had logged in with new group. Must have been compiled into the shell; see the version
variable.

nice nice [+ n] command
Change the execution priority for command, or, if none is given, change priority for the current shell. (See also nice in Chapter
3, "Linux Commands".) The priority range is -20 to 20, with a default of 4. The range seems backward: -20 gives the highest
priority (fastest execution); 20 gives the lowest. Only a privileged user may specify a negative number.

+n
Add n to the priority value (lower job priority).
-n

Subtract n from the priority value (raise job priority). Privileged users only.

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Built-in csh and tcsh Commands (Linux in a Nutshell, 3rd Edition)
nohup nohup [command]
"No hangup signals." Do not terminate command after terminal line is closed (i. e., when you hang up from a phone or log out).
Use without command in shell scripts to keep script from being terminated. (See also nohup in Chapter 3, "Linux Commands".)

notify notify [jobID]
Report immediately when a background job finishes (instead of waiting for you to exit a long editing session, for example). If
no jobID is given, the current background job is assumed.

onintr onintr label
onintr -onintr

"On interrupt." Used in shell scripts to handle interrupt signals (similar to bash's trap 2 and trap "" 2 commands). The first
form is like a goto label. The script will branch to label: if it catches an interrupt signal (e. g., Ctrl-C). The second form lets the
script ignore interrupts. This is useful at the beginning of a script or before any code segment that needs to run unhindered (e. g.,
when moving files). The third form restores interrupt handling that was previously disabled with onintr -.

Example
onintr cleanup Go to "cleanup" on interrupt. .Shell script commands. cleanup:Label for interruptsonintr -Ignore additional interrupts file:/// E|/ O'Reilly/ O'Reilly% 20-% 20Linux% 20in% 20a% 20Nutshell,% 203rd% 20Edition/ Pages/ ch08_ 09. htm (28 of 40) [15/ 05/ 2002 18: 10: 11] 625
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rm -f $tmpfiles Remove any files createdexit 2 Exit with an error status

popd popd [options]
Remove the current entry from the directory stack, or remove the nth entry from the stack and print the stack that remains. The
current entry has number 0 and appears on the left. See also dirs and pushd.

Options
+n
Specify nth entry.
-l
Expand ~ notation.
-n
Wrap long lines.
-p
Override the pushdsilent shell variable, which otherwise prevents the printing of the final stack.
-v
Print precisely one directory per line.
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printenv printenv [variable]
Print all (or one specified) environment variables and their values.

pushd pushd name
pushd [options]
pushd
The first form changes the working directory to name and adds it to the directory stack. The second form rotates the nth entry to
the beginning, making it the working directory. (Entry numbers begin at 0.) With no arguments, pushd switches the first two
entries and changes to the new current directory. The +n, -l, -n, and -v options behave the same as in popd. See also dirs and
popd.

Examples
% dirs/home/ bob /usr %pushd /etc Add /etc to directory stack /etc /home/ bob /usr %pushd +2 Switch to third directory /usr /etc /home/ bob %pushd Switch top two directories /etc /usr /home/ bob %popd Discard current entry; go to next /usr /home/ bob

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rehash rehash
Recompute the internal hash table for the PATH variable. Use rehash whenever a new command is created during the current
session. This allows the PATH variable to locate and execute the command. (If the new command resides in a directory not
listed in PATH, add this directory to PATH before rehashing.) See also unhash.

repeat repeat n command
Execute n instances of command.
Examples
Print three copies of memo:
% repeat 3 pr memo | lpRead 10 lines from the terminal and store in item_ list:
% repeat 10 line > item_ listAppend 50 boilerplate files to report:
% repeat 50 cat template >> report

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sched sched [options]
sched time command
tcsh only. Without options, print all scheduled events. The second form schedules an event.
time should be specified in hh: mm form (e. g., 13: 00).
Options
+hh: mm
Schedule event to take place hh: mm from now.
-n
Remove nth item from schedule.

set set variable= value
set [option] variable[ n]= value
set
Set variable to value, or if multiple values are specified, set the variable to the list of words in the value list. If an index n is
specified, set the nth word in the variable to value. (The variable must already contain at least that number of words.) With no
arguments, display the names and values of all set variables. See also "Predefined Shell Variables" earlier in this chapter.

Option
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Built-in csh and tcsh Commands (Linux in a Nutshell, 3rd Edition)
-r
tcsh only. List only read-only variables, or set specified variable to read-only.
Examples
% set list=( yes no maybe) Assign a wordlist %set list[ 3]= maybe Assign an item in existing wordlist %set quote=" Make my day" Assign a variable %set x= 5 y= 10 history= 100 Assign several variables %set blank Assign a null value to blank

setenv setenv [name [value]]
Assign a value to an environment variable name. By convention, name is uppercase. value can be a single word or a quoted
string. If no value is given, the null value is assigned. With no arguments, display the names and values of all environment
variables. setenv is not necessary for the PATH variable, which is automatically exported from path.

settc settc capability value
tcsh only. Set terminal capability to value.

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setty setty [options] [+|-mode]
tcsh only. Do not allow shell to change specified tty modes. By default, act on the execute set.
Options
+mode
Without arguments, list all modes in specified set that are on. Otherwise, set specified mode to on.
-mode
Without arguments, list all modes in specified set that are off. Otherwise, set specified mode to on.
-a
List all modes in specified set.
-d
Act on the edit set of modes (used when editing commands).
-q
Act on the quote set of modes (used when entering characters verbatim).
-x
Act on the execute set of modes (default) (used when executing examples).
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Built-in csh and tcsh Commands (Linux in a Nutshell, 3rd Edition)
shift shift [variable]
If variable is given, shift the words in a wordlist variable (i. e., name[ 2] becomes name[ 1]). With no argument, shift the
positional parameters (command-line arguments) (i. e., $2 becomes $1). shift is typically used in a while loop. See additional
example under while.

Example
while ($# argv) While there are argumentsif (-f $argv[ 1]) wc -l $argv[ 1] else echo "$ argv[ 1] is not a regular file" endif shiftGet the next argumentend

source source [-h] script [args]
Read and execute commands from a C-shell script. With -h, the commands are added to the history list but aren't executed. For
tcsh only, arguments can be passed to the script and are put in argv.

Example
source ~/. cshrc

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stop stop [jobIDs]
Suspend the current background jobs or the background jobs specified by jobIDs; this is the complement of Ctrl-Z or suspend.

suspend suspend
Suspend the current foreground job; same as Ctrl-Z. Often used to stop an su command.

switch switch
Process commands depending on the value of a variable. When you need to handle more than three choices, switch is a useful
alternative to an if-then-else statement. If the string variable matches pattern1, the first set of commands is executed; if string
matches pattern2, the second set of commands is executed; and so on. If no patterns match, execute commands under the
default case. string can be specified using command substitution, variable substitution, or filename expansion. Patterns can be
specified using the pattern-matching symbols *, ?, and []. breaksw is used to exit the switch. If breaksw is omitted (which is
rarely done), the switch continues to execute another set of commands until it reaches a breaksw or endsw. Following is the
general syntax of switch, side-by-side with an example that processes the first command-line argument:

switch (string) switch ($ argv[ 1])case pattern1: case -[ nN]:commands nroff $file | lpbreaksw breakswcase pattern2: case -[ Pp]:commands pr $file | lpbreaksw breakswcase pattern3: case -[ Mm]:commands more $filebreaksw breaksw. case -[ Ss]:

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. sort $file. breakswdefault: default:commands echo "Error --no such option" exit 1breaksw breakswendsw endsw

telltc telltc
tcsh only. Print all terminal capabilities and their values.

time time [command]
Execute a command and show how much time it uses. With no argument, time can be used in a shell script to time the script.

umask umask [nnn]
Display file creation mask or set file creation mask to octal nnn. The file creation mask determines which permission bits are
turned off. With no nnn, print the current mask.

unalias unalias pattern
Remove all aliases whose names match pattern from the alias list. See alias for more information.

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Built-in csh and tcsh Commands (Linux in a Nutshell, 3rd Edition)
uncomplete uncomplete pattern
tcsh only. Remove completions (specified by complete) whose names match pattern.

unhash unhash
Remove internal hash table. The shell stops using hashed values and searches the path directories to locate a command. See
also rehash.

unlimit unlimit [-h] [resource]
Remove the allocation limits on resource. If resource is not specified, remove limits for all resources. See limit for more
information. With -h, remove hard limits. This command can be run only by a privileged user.

unset unset variables
Remove one or more variables. Variable names may be specified as a pattern, using filename metacharacters. Does not remove
read-only variables. See set.

unsetenv unsetenv variable
Remove an environment variable. Filename matching is not valid. See setenv.

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wait wait
Pause in execution until all child processes complete, or until an interrupt signal is received.

watchlog watchlog
tcsh only. Same as log. Must have been compiled into the shell; see the version shell variable.

where where command
tcsh only. Display all aliases, built-ins, and executables named command.

which which command
tcsh only. Report which version of command will be executed. Same as the executable which, but faster, and checks tcsh built-ins.

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while while (expression)
commands
end
As long as expression is true (evaluates to nonzero), evaluate commands between while and end. break and continue can be
used to terminate or continue the loop.

Example
set user = (alice bob carol ted) while ($ argv[ 1] != $user[ 1])Cycle through each user, checking for a matchshift user If we cycled through with no match...if ($# user == 0) then echo "$ argv[ 1] is not on the list of users" exit 1 endif end

8.8. Job Control 9. Pattern Matching
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Pattern Matching (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

Chapter 9. Pattern Matching
Contents:
Filenames Versus Patterns
Metacharacters, Listed by Linux Program
Metacharacters
Examples of Searching

A number of Linux text-editing utilities let you search for and, in some cases change, text
patterns rather than fixed strings. These utilities include the editing programs ed, ex, vi, and
sed; the awk scripting language; and the commands grep and egrep. Text patterns (also
called regular expressions) contain normal characters mixed with special characters (also
called metacharacters).

Perl's regular expression support is so rich that it does not fit into the tables in this chapter;
you can find a description in the O'Reilly books Perl in a Nutshell, Perl 5 Pocket Reference,
or Programming Perl. The Emacs editor also provides regular expressions similar to those
shown in this chapter.

ed and ex are hardly ever used as standalone, interactive editors nowadays. But ed can be
found as a batch processor invoked from shell scripts, and ex commands often are invoked
within vi through the colon (:) command. We use vi in this chapter to refer to the regular
expression features supported by both vi and the ex editor on which it is based.

sed and awk are widely used in shell scripts and elsewhere as filters to alter text.
This chapter presents the following information:
l Filenames versus patterns

l List of metacharacters available to each program
l Description of metacharacters

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Pattern Matching (Linux in a Nutshell, 3rd Edition)
l Examples
A thorough guide to pattern matching can be found in the Nutshell handbook Mastering
Regular Expressions by Jeffrey E. F. Friedl.

9.1. Filenames Versus Patterns
Metacharacters used in pattern matching are different from those used for filename expansion.
When you issue a command on the command line, special characters are seen first by the
shell, then by the program; therefore, unquoted metacharacters are interpreted by the shell for
filename expansion. The command:

$ grep [A-Z]* chap[ 12]could, for example, be interpreted by the shell as:
$ grep Array. c Bug. c Comp. c chap1 chap2and grep then would try to find the pattern "Array. c" in files Bug. c, Comp. c, chap1, and
chap2. To bypass the shell and pass the special characters to grep, use quotes:

$ grep "[ A-Z]*" chap[ 12]Double quotes suffice in most cases, but single quotes are the safest bet.
Note also that * and ? have subtly different meanings in pattern matching and filename
expansion.

8.9. Built-in csh and tcsh
Commands
9.2. Metacharacters, Listed
by Linux Program

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Metacharacters, Listed by Linux Program (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

9.2. Metacharacters, Listed by Linux Program
Some metacharacters are valid for one program but not for another. Those that are available to
a given program are marked by a bullet ( ) in the following table. Notes are provided after the
table, and full descriptions of metacharacters are in the following section.

Symbol ed vi sed awk grep egrep Action
. Match any character (can match newline in gawk).
* Match zero or more preceding.
^ Match beginning of line or string.
$ Match end of line or string.
\ Escape character following.
[] Match one from a list or range.
 Store pattern for later replay.
\n Reuse matched text stored in nth .
{} Match a range of instances.
\{\} Match a range of instances.
\<\> Match word's beginning or end.
+ Match one or more preceding.
? Match zero or one preceding.
| Separate choices to match.
() Group expressions to match.

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Metacharacters, Listed by Linux Program (Linux in a Nutshell, 3rd Edition)
On some Linux systems, grep is a link to egrep, so whenever you run grep you actually get
egrep behavior.

In ed, vi, and sed, when you perform a search-and-replace (substitute) operation, the
metacharacters in this table apply to the pattern you are searching for but not to the string
replacing it.

In awk, {} is specified in the POSIX standard and is supported by gawk if you run it with the -Wre-
interval option.

In ed, vi, and sed, the following additional metacharacters are valid only in a replacement
pattern:

Symbol ex sed ed Action
\ Escape character following.
\n Reuse matched text stored in nth .
& Reuse previous search pattern.
~ Reuse previous replacement pattern.
\e Turn off previous \L or \U.
\E Turn off previous /L or /U.
\l Change single following character to lowercase.
\L Change following characters to lowercase until /E encountered.
\u Change single following character to uppercase.
\U Change following characters to uppercase until \E encountered.

9. Pattern Matching 9.3. Metacharacters
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Metacharacters (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

9.3. Metacharacters
The following characters have special meaning in search patterns:

Character Meaning
. Match any single character except newline.

*Match any number (or none) of the single character that immediately precedes
it. The preceding character also can be a regular expression (e. g., since . (dot)
means any character, .* means match any number of any character --except
newlines).

^ Match the beginning of the line or string.
$ Match the end of the line or string.

[ ]Match any one of the enclosed characters. A hyphen (-) indicates a range of
consecutive characters. A circumflex (^) as the first character in the brackets
reverses the sense: it matches any one character not in the list. A hyphen or
close bracket (]) as the first character is treated as a member of the list. All
other metacharacters are treated as members of the list.

[^ ] Match anything except enclosed characters.

\{ n, m\}
Match a range of occurrences of the single character that immediately
precedes it. The preceding character also can be a regular expression. \{ n\}
matches exactly n occurrences, \{ n,\} matches at least n occurrences, and
\{ n, m\} matches any number of occurrences between n and m.

{n, m} Like \{ n, m\}. Available in grep by default and in gawk with the -Wre-interval option.

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Metacharacters (Linux in a Nutshell, 3rd Edition)
\ Turn off the special meaning of the character that follows.

Save the matched text enclosed between $ and $ in a special holding space.
Up to nine patterns can be saved on a single line. They can be "replayed" in
the same pattern or within substitutions by the escape sequences \1 to \9.

\n Reuse matched text stored in nth .

() In egrep and gawk, save the matched text enclosed between $ and $ in a holding space to be replayed in substitutions by the escape sequences \1 to \9.
\<\> Match the beginning (\<) or end (\>) of a word.
+ Match one or more instances of preceding regular expression.
? Match zero or one instance of preceding regular expression.
| Match the regular expression specified before or after.
() Group regular expressions.

Many utilities support POSIX character lists, which are useful for matching non-ASCII
characters in languages other than English. These lists are recognized only within [] ranges. A
typical use would be [[: lower:]], which in English is the same as [a-z].

The following table lists POSIX character lists:

Notation Action
[: alnum:] Alphanumeric characters
[: alpha:] Alphabetic characters, uppercase and lowercase
[: blank:] Printable whitespace: spaces and tabs but not control characters
[: cntrl:] Control characters, such as ^A through ^Z
[: digit:] Decimal digits
[: graph:] Printable characters, excluding whitespace
[: lower:] Lowercase alphabetic characters
[: print:] Printable characters, including whitespace but not control characters
[: punct:] Punctuation, a subclass of printable characters
[: space:] Whitespace, including spaces, tabs, and some control characters

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[: upper:] Uppercase alphabetic characters
[: xdigit:] Hexadecimal digits

The following characters have special meaning in replacement patterns:
Character Meaning
\ Turn off the special meaning of the character that follows.

\n Restore the nth pattern previously saved by $ and $. n is a number from 1 to 9, matching the patterns searched sequentially from left to right.
& Reuse the search pattern as part of the replacement pattern.
~ Reuse the previous replacement pattern in the current replacement pattern.
\e End replacement pattern started by \L or \U.\E End replacement pattern started by \L or \U.\l Convert first character of replacement pattern to lowercase.
\L Convert replacement pattern to lowercase.
\u Convert first character of replacement pattern to uppercase.
\U Convert replacement pattern to uppercase.

9.2. Metacharacters, Listed
by Linux Program
9.4. Examples of Searching

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Examples of Searching (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
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9.4. Examples of Searching
When used with grep or egrep, regular expressions normally are surrounded by quotes to avoid interpretation by
the shell. (If the pattern contains a $, you must use single quotes, as in '$ 200', or escape the $, as in "\$ 200".)
When used with ed, vi, sed, and awk, regular expressions usually are surrounded by / (although any delimiter
works). Here are some sample patterns:

Pattern What does it match?
bag The string bag.
^bag "bag" at beginning of line or string.
bag$ "bag" at end of line or string.
^bag$ "bag" as the only text on line.
[Bb] ag "Bag" or "bag."
b[ aeiou] g Second character is a vowel.
b[^ aeiou] g Second character is not a vowel.
b. g Second character is any character except newline.
^...$ Any line containing exactly three characters.
^\. Any line that begins with a dot.
^\.[ a-z][ a-z] Same, followed by two lowercase letters (e. g., troff requests).
^\.[ a-z]\{ 2\} Same as previous, grep or sed only.
^[^.] Any line that doesn't begin with a dot.
bugs* "bug," "bugs", "bugss", etc.
"word" A word in quotes.
"* word"* A word, with or without quotes.
[A-Z][ A-Z]* One or more uppercase letters.
[A-Z]+ Same, egrep or awk only.
[A-Z].* An uppercase letter, followed by zero or more characters.
[A-Z]* Zero or more uppercase letters.
[a-zA-Z] Any letter.

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Examples of Searching (Linux in a Nutshell, 3rd Edition)
[0-9A-Za-z]+ Any alphanumeric sequence.
egrep or awk pattern What does it match?
[567] One of the numbers 5, 6, or 7
five| six| seven One of the words five, six, or seven
80[ 23]? 86 8086, 80286, or 80386
compan( y| ies) company or companies

vi pattern What does it match?
\< the Words like theater or the
the\> Words like breathe or the
\< the\> The word the

sed or grep pattern What does it match?
0\{ 5,\} Five or more zeros in a row
[0-9]\{ 3\}-[ 0-9]\{ 2\}-[ 0-9]\{ 4\} Social security number (nnn-nn-nnnn)

9.4.1. Examples of Searching and Replacing
The following examples show the metacharacters available to sed and vi. We have shown vi commands with an
initial colon because that is how they are invoked within vi. A space is marked by a ; a tab is marked by tab.

Command Result
s/.*/(&)/ Reproduce the entire line, but add parentheses.
s/.*/ mv & &. old/ Change a wordlist (one word per line) into mv commands.
/^$/ d Delete blank lines.
:g/^$/ d Same as previous, in vi editor.
/^[ tab]*$/ d Delete blank lines, plus lines containing spaces or tabs.
:g/^[ tab]*$/ d Same as previous, in vi editor.
s/ */ /g Turn one or more spaces into one space.
:% s/ */ /g Same as previous, in vi editor.
:s/[ 0-9]/ Item &:/ Turn a number into an item label (on the current line).
:s Repeat the substitution on the first occurrence.
:& Same as previous.
:sg Same, but for all occurrences on the line.
:& g Same as previous.

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Examples of Searching (Linux in a Nutshell, 3rd Edition)
:%& g Repeat the substitution globally.
:.,$ s/ Fortran/\ U&/ g Change word to uppercase, on current line to last line.
:% s/.*/\ L&/ Lowercase entire file.
:s/\<./\ u&/ g Uppercase first letter of each word on current line. (Useful for titles.)
:% s/ yes/ No/ g Globally change a word (yes) to another word (No).
:% s/ Yes/~/ g Globally change a different word to No (previous replacement).

Finally, here are some sed examples for transposing words. A simple transposition of two words might look like
this:

s/ die or do/ do or die/ Transpose wordsThe real trick is to use hold buffers to transpose variable patterns. For example:
s/$[ Dd] ie$ or $[ Dd] o$/\ 2 or\ 1/ Transpose, using hold buffers

9.3. Metacharacters 10. The Emacs Editor
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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The Emacs Editor (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

Chapter 10. The Emacs Editor
Contents:
Introduction
Typical Problems
Summary of Commands by Group
Summary of Commands by Key
Summary of Commands by Name

This chapter presents the following topics:
l Introduction
l Typical problems
l Summary of Emacs commands by group
l Summary of Emacs commands by key
l Summary of Emacs commands by name

10.1. Introduction
Although Emacs is not part of Linux, this text editor is found on many Unix systems because
it is a popular alternative to vi. Many versions are available. This book documents GNU
Emacs, which is available from the Free Software Foundation in Cambridge, Massachusetts.
For more information, see the O'Reilly book Learning GNU Emacs, 2d ed., by Debra
Cameron, Bill Rosenblatt, and Eric Raymond.

To start an Emacs editing session, type:
emacs [file]

9.4. Examples of Searching 10.2. Typical Problems
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The Emacs Editor (Linux in a Nutshell, 3rd Edition)
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Typical Problems (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

10.2. Typical Problems
A very common problem is that the Del or Backspace key on the terminal does not delete the
character before the cursor, as it should. Instead, it invokes a help prompt. This problem is
caused by an incompatible terminal. A fairly robust fix is to create a file named .emacs in your
home directory (or edit one that's already there) and add the following lines:

(keyboard-translate ?\ C-h ?\ C-?) (keyboard-translate ?\ C-\\ ?\ C-h)

Now the Del or Backspace kill should work, and you can invoke help by pressing C-\ (an
arbitrarily chosen key sequence).

Another potential problem is that on some systems, C-s causes the terminal to hang. This is
due to an old-fashioned handshake protocol between the terminal and the system. You can
restart the terminal by pressing C-q, but that doesn't help you enter commands that contain the
sequence C-s. The solution (aside from using a more modern dial-in protocol) is to create new
key bindings that replace C-s or to enter those commands as M-x command-name.

10.2.1. Notes on the Tables
Emacs commands use the Ctrl key and the Meta key. Most modern terminals provide a key
named Alt that functions as a Meta key. In this section, the notation C-indicates that you
should hold down the Ctrl key and press the character that follows, while M-indicates that the
Meta or Alt key is pressed in the same way, along with the character that follows. As an
alternative to Meta or Alt, you can press the Esc key, release it, and press the character. You
might want to do this if you have any problems with controlling windows capturing the Alt
key (which sometimes happens).

In the command tables that follow, the first column lists the keystroke and the last column
describes it. When there is a middle column, it lists the command name. The command can be
executed by typing M-x followed by the command name; you have to do this when the
binding is listed as "( none)." If you're unsure of the full command name, you can type a space
or a carriage return, and Emacs will list possible completions of what you've typed so far.

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Typical Problems (Linux in a Nutshell, 3rd Edition)
Because Emacs is such a comprehensive editor, containing hundreds of commands, some
commands must be omitted for the sake of preserving a "quick" reference. You can browse
the command set by typing C-h (for help) and then b to get a list of the key bindings[ 6] or M-x

followed by a space or Tab to get the command names.

[6] If you want to learn to create your own key bindings, see Learning GNU
Emacs (O'Reilly).

10.2.2. Modes
One of the features that makes Emacs popular is its editing modes. The modes set up an
environment designed for the type of editing you are doing, with features like having
appropriate key bindings available and automatically indenting according to standard
conventions for that type of document. There are modes for various programming languages
like C or Perl, for text processing (e. g., SGML or even straight text), and many more. One
particularly useful mode is Dired (Directory Editor), which has commands that let you
manage directories. For a full discussion of modes, see Learning GNU Emacs, mentioned at
the beginning of this chapter, or the Emacs Info documentation system (C-h i).

10.2.3. Absolutely Essential Commands
If you're just getting started with Emacs, here's a short list of the most important commands to
know:

Binding Action
C-h Enter the online help system.
C-x C-s Save the file.
C-x C-c Exit Emacs.
C-x u Undo last edit (can be repeated).
C-g Get out of current command operation.
C-p Up by one line.
C-n Down by one line.
C-f Forward by one character.
C-b Back by one character.
C-v Forward by one screen.
M-v Backward by one screen.

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C-s Search forward for characters.
C-r Search backward for characters.
C-d Delete current character.
Del Delete previous character.
Backspace Delete previous character.

10. The Emacs Editor 10.3. Summary of
Commands by Group

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10.3. Summary of Commands by Group
Reminder: Tables list keystrokes, command name, and description. C-indicates the Control
key; M-indicates the Meta key.

10.3.1. File-Handling Commands

Binding Command Action
C-x C-f find-file Find file and read it.

C-x C-v find-alternate-file Read another file; replace the one read currently in the buffer.
C-x i insert-file Insert file at cursor position.
C-x C-s save-buffer Save file. (If terminal hangs, C-q restarts.)
C-x C-w write-file Write buffer contents to file.
C-x C-c save-buffers-kill-emacs Exit Emacs.
C-z suspend-emacs Suspend Emacs (use exit or fg to restart).

10.3.2. Cursor Movement Commands
Some words are emphasized in the Action column to help you remember the binding for the
command.

Binding Command Action
C-f forward-char Move forward one character (right).
C-b backward-char Move backward one character (left).
C-p previous-line Move to previous line (up).

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C-n next-line Move to next line (down).
M-f forward-word Move one word forward.
M-b backward-word Move one word backward.
C-a beginning-of-line Move to beginning of line.
C-e end-of-line Move to end of line.
M-a backward-sentence Move backward one sentence.
M-e forward-sentence Move forward one sentence.
M-{ backward-paragraph Move backward one paragraph.
M-} forward-paragraph Move forward one paragraph.
C-v scroll-up Move forward one screen.
M-v scroll-down Move backward one screen.
C-x [ backward-page Move backward one page.
C-x ] forward-page Move forward one page.
M-> end-of-buffer Move to end-of-file.
M-< beginning-of-buffer Move to beginning of file.
(none) goto-line Go to line n of file.
(none) goto-char Go to character n of file.
C-l recenter Redraw screen with current line in the center.
M-n digit-argument Repeat the next command n times.
C-u n universal-argument Repeat the next command n times.

10.3.3. Deletion Commands
Binding Command Action
Del backward-delete-char Delete previous character.
C-d delete-char Delete character under cursor.
M-Del backward-kill-word Delete previous word.

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M-d kill-word Delete the word the cursor is on.
C-k kill-line Delete from cursor to end-of-line.
M-k kill-sentence Delete sentence the cursor is on.
C-x Del backward-kill-sentence Delete previous sentence.
C-y yank Restore what you've deleted.

C-w kill-region Delete a marked region (see Section 10.3.4, "Paragraphs and Regions").
(none) backward-kill-paragraph Delete previous paragraph.
(none) kill-paragraph Delete from the cursor to the end of the paragraph.

10.3.4. Paragraphs and Regions
Binding Command Action
C-@ set-mark-command Mark the beginning (or end) of a region.
C-Space (Same as preceding) (Same as preceding)
C-x C-p mark-page Mark page.
C-x C-x exchange-point-and-mark Exchange location of cursor and mark.
C-x h mark-whole-buffer Mark buffer.
M-q fill-paragraph Reformat paragraph.
(none) fill-region Reformat individual paragraphs within a region.
M-h mark-paragraph Mark paragraph.
M-{ backward-paragraph Move backward one paragraph.
M-} forward-paragraph Move forward one paragraph.
(none) backward-kill-paragraph Delete previous paragraph.
(none) kill-paragraph Delete from the cursor to the end of the paragraph.

10.3.5. Stopping and Undoing Commands

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Binding Command Action
C-g keyboard-quit Abort current command.
C-x u advertised-undo Undo last edit (can be done repeatedly).

(none) revert-buffer Restore buffer to the state it was in when the file was last saved (or auto-saved).

10.3.6. Transposition Commands
Binding Command Action
C-t transpose-chars Transpose two letters.
M-t transpose-words Transpose two words.
C-x C-t transpose-lines Transpose two lines.
(none) transpose-sentences Transpose two sentences.
(none) transpose-paragraphs Transpose two paragraphs.

10.3.7. Capitalization Commands
Binding Command Action
M-c capitalize-word Capitalize first letter of word.
M-u upcase-word Uppercase word.
M-l downcase-word Lowercase word.
M--M-c negative-argument; capitalize-word Capitalize previous word.
M--M-u negative-argument; upcase-word Uppercase previous word.
M--M-l negative-argument; downcase-word Lowercase previous word.
(none) capitalize-region Capitalize initial letters in region.
C-x C-u upcase-region Uppercase region.
C-x C-l downcase-region Lowercase region.

10.3.8. Incremental Search Commands
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Summary of Commands by Group (Linux in a Nutshell, 3rd Edition)
Binding Command Action
C-s isearch-forward Start or repeat incremental search forward.
C-r isearch-backward Start or repeat incremental search backward.
Return (none) Exit a successful search.
C-g keyboard-quit Cancel incremental search; return to starting point.
Del (none) Delete incorrect character of search string.
M-C-r isearch-backward-regexp Incremental search backward for regular expression.
M-C-s isearch-forward-regexp Incremental search forward for regular expression.

10.3.9. Word Abbreviation Commands
Binding Command Action
(none) abbrev-mode Enter (or exit) word abbreviation mode.

C-x a -inverse-add-global-abbrev Define previous word as global (mode-independent) abbreviation.

C-x a i l inverse-add-mode-abbrev Define previous word as mode-specific abbreviation.
(none) unexpand-abbrev Undo the last word abbreviation.
(none) write-abbrev-file Write the word abbreviation file.
(none) edit-abbrevs Edit the word abbreviations.
(none) list-abbrevs View the word abbreviations.
(none) kill-all-abbrevs Kill abbreviations for this session.

10.3.10. Buffer Manipulation Commands
Binding Command Action
C-x b switch-to-buffer Move to specified buffer.
C-x C-b list-buffers Display buffer list.
C-x k kill-buffer Delete specified buffer.

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(none) kill-some-buffers Ask about deleting each buffer.
(none) rename-buffer Change buffer name to specified name.
C-x s save-some-buffers Ask whether to save each modified buffer.

10.3.11. Window Commands
Binding Command Action
C-x 2 split-window-vertically Divide the current window in two vertically, resulting in one window on top of the other.

C-x 3 split-window-horizontally Divide the current window in two horizontally, resulting in two side-by-side windows.
C-x > scroll-right Scroll the window right.
C-x < scroll-left Scroll the window left.
C-x o other-window Move to the other window.
C-x 0 delete-window Delete current window.
C-x 1 delete-other-windows Delete all windows but this one.
(none) delete-windows-on Delete all windows on a given buffer.
C-x ^ enlarge-window Make window taller.
(none) shrink-window Make window shorter.
C-x } enlarge-window-horizontally Make window wider.
C-x { shrink-window-horizontally Make window narrower.
M-C-v scroll-other-window Scroll other window.
C-x 4 f find-file-other-window Find a file in the other window.
C-x 4 b switch-to-buffer-other-window Select a buffer in the other window.
C-x 5 f find-file-other-frame Find a file in a new frame.
C-x 5 b switch-to-buffer-other-frame Select a buffer in another frame.
(none) compare-windows Compare two buffers; show first difference.

10.3.12. Special Shell Mode Characters
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Summary of Commands by Group (Linux in a Nutshell, 3rd Edition)
Binding Command Action
C-c C-c interrupt-shell-subjob Terminate the current job.
C-c C-d shell-send-eof End-of-file character.
C-c C-u kill-shell-input Erase current line.
C-c C-w backward-kill-word Erase the previous word.
C-c C-z stop-shell-subjob Suspend the current job.

10.3.13. Indentation Commands
Binding Command Action

C-x . set-fill-prefix
Prepend each line in paragraph with characters from
beginning of line up to cursor column; cancel prefix
by typing this command in column 1.

(none) indented-text-mode Major mode: each tab defines a new indent for subsequent lines.
(none) text-mode Exit indented text mode; return to text mode.
M-C-\ indent-region Indent a region to match first line in region.
M-m back-to-indentation Move cursor to first character on line.
M-^ delete-indentation Join this line to the previous line.
M-C-o split-line Split line at cursor; indent to column of cursor.
(none) fill-individual-paragraphs Reformat indented paragraphs, keeping indentation.

10.3.14. Centering Commands
Binding Command Action
(none) center-line Center line that cursor is on.
(none) center-paragraph Center paragraph that cursor is on.
(none) center-region Center currently defined region.

10.3.15. Macro Commands
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Summary of Commands by Group (Linux in a Nutshell, 3rd Edition)
Binding Command Action
C-x ( start-kbd-macro Start macro definition.
C-x ) end-kbd-macro End macro definition.
C-x e call-last-kbd-macro Execute last macro defined.

M-n C-x e digit-argument and call-last-kbd-macro Execute last macro defined n times.

C-u C-x ( start-kbd-macro Execute last macro defined, then add keystrokes.
(none) name-last-kbd-macro Name last macro you created (before saving it).
(none) insert-last-keyboard-macro Insert the macro you named into a file.
(none) load-file Load macro files you've saved.
(none) macroname Execute a keyboard macro you've saved.
C-x q kbd-macro-query Insert a query in a macro definition.
C-u C-x q (none) Insert a recursive edit in a macro definition.
M-C-c exit-recursive-edit Exit a recursive edit.

10.3.16. Detail Information Help Commands
Binding Command Action
C-h a command-apropos What commands involve this concept?

(none) apropos What commands, functions, and variables involve this concept?
C-h c describe-key-briefly What command does this keystroke sequence run?
C-h b describe-bindings What are all the key bindings for this buffer?

C-h k describe-key What command does this keystroke sequence run, and what does it do?

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Summary of Commands by Group (Linux in a Nutshell, 3rd Edition)
C-h l view-lossage What are the last 100 characters I typed?
C-h w where-is What is the key binding for this command?
C-h f describe-function What does this function do?
C-h v describe-variable What does this variable mean, and what is its value?
C-h m describe-mode Tell me about the mode the current buffer is in.
C-h s describe-syntax What is the syntax table for this buffer?

10.3.17. Help Commands
Binding Command Action
C-h t help-with-tutorial Run the Emacs tutorial.
C-h i info Start the Info documentation reader.
C-h n view-emacs-news View news about updates to Emacs.
C-h C-c describe-copying View the Emacs General Public License.
C-h C-d describe-distribution View information on ordering Emacs from the FSF.
C-h C-w describe-no-warranty View the (non) warranty for Emacs.

10.2. Typical Problems 10.4. Summary of
Commands by Key

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Linux in a Nutshell, 3rd
Edition

10.4. Summary of Commands by Key
Emacs commands are presented next in two alphabetical lists. Tables list keystrokes,
command name, and description. C-indicates the Ctrl key; M-indicates the Meta key.

10.4.1. Control-Key Sequences

Binding Command Action
C-@ set-mark-command Mark the beginning (or end) of a region.
C-Space (Same as preceding) (Same as preceding)
C-] abort-recursive-edit Exit recursive edit and exit query-replace.
C-a beginning-of-line Move to beginning of line.
C-b backward-char Move backward one character (left).
C-c C-c interrupt-shell-subjob Terminate the current job.
C-c C-d shell-send-eof End-of-file character.
C-c C-u kill-shell-input Erase current line.
C-c C-w backward-kill-word Erase the previous word.
C-c C-z stop-shell-subjob Suspend the current job.
C-d delete-char Delete character under cursor.
C-e end-of-line Move to end of line.
C-f forward-char Move forward one character (right).
C-g keyboard-quit Abort current command.
C-h help-command Enter the online help system.

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C-h a command-apropos What commands involve this concept?
C-h b describe-bindings What are all the key bindings for this buffer?

C-h c describe-key-briefly What command does this keystroke sequence run?
C-h C-c describe-copying View the Emacs General Public License.
C-h C-d describe-distribution View information on ordering Emacs from the FSF.
C-h C-w describe-no-warranty View the (non) warranty for Emacs.
C-h f describe-function What does this function do?
C-h i info Start the Info documentation reader.

C-h k describe-key What command does this keystroke sequence run, and what does it do?
C-h l view-lossage What are the last 100 characters I typed?
C-h m describe-mode Tell me about the mode the current buffer is in.
C-h n view-emacs-news View news about updates to Emacs.
C-h s describe-syntax What is the syntax table for this buffer?
C-h t help-with-tutorial Run the Emacs tutorial.

C-h v describe-variable What does this variable mean, and what is its value?
C-h w where-is What is the key binding for this command?
C-k kill-line Delete from cursor to end-of-line.
C-l recenter Redraw screen with current line in the center.
C-n next-line Move to next line (down).
C-p previous-line Move to previous line (up).

C-q quoted-insert Insert next character typed. Useful for inserting a control character.

C-r isearch-backward Start or repeat nonincremental search backward.
C-r (none) Enter recursive edit (during query replace).
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C-s isearch-forward Start or repeat nonincremental search forward.
C-t transpose-chars Transpose two letters.
C-u n universal-argument Repeat the next command n times.

C-u C-x ( start-kbd-macro Execute last macro defined, then add keystrokes.
C-u C-x q (none) Insert recursive edit in a macro definition.
C-v scroll-up Move forward one screen.
C-w kill-region Delete a marked region.
C-x ( start-kbd-macro Start macro definition.
C-x ) end-kbd-macro End macro definition.
C-x [ backward-page Move backward one page.
C-x ] forward-page Move forward one page.
C-x ^ enlarge-window Make window taller.
C-x { shrink-window-horizontally Make window narrower.
C-x } enlarge-window-horizontally Make window wider.
C-x < scroll-left Scroll the window left.
C-x > scroll-right Scroll the window right.

C-x . set-fill-prefix
Prepend each line in paragraph with
characters from beginning of line up to cursor
column; cancel prefix by typing this
command in column 1.

C-x 0 delete-window Delete current window.
C-x 1 delete-other-windows Delete all windows but this one.

C-x 2 split-window-vertically Divide current window in two vertically, resulting in one window on top of the other.

C-x 3 split-window-horizontally Divide current window in two horizontally, resulting in two side-by-side windows.
C-x 4 b switch-to-buffer-other-window Select a buffer in the other window.
C-x 4 f find-file-other-window Find a file in the other window.

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C-x 5 b switch-to-buffer-other-frame Select a buffer in another frame.
C-x 5 f find-file-other-frame Find a file in a new frame.

C-x a -inverse-add-global-abbrev Define previous word as global (mode-independent) abbreviation.

C-x a i l inverse-add-mode-abbrev Define previous word as mode-specific abbreviation.
C-x b switch-to-buffer Move to the buffer specified.
C-x C-b list-buffers Display the buffer list.
C-x C-c save-buffers-kill-emacs Exit Emacs.
C-x C-f find-file Find file and read it.
C-x C-l downcase-region Lowercase region.
C-x C-p mark-page Place cursor and mark around whole page.
C-x C-q (none) Toggle read-only status of buffer.
C-x C-s save-buffer Save file. (If terminal hangs, C-q restarts.)
C-x C-t transpose-lines Transpose two lines.
C-x C-u upcase-region Uppercase region.

C-x C-v find-alternate-file Read an alternate file, replacing the one currently in the buffer.
C-x C-w write-file Write buffer contents to file.
C-x C-x exchange-point-and-mark Exchange location of cursor and mark.
C-x Del backward-kill-sentence Delete previous sentence.
C-x e call-last-kbd-macro Execute last macro defined.
C-x h mark-whole-buffer Place cursor and mark around whole buffer.
C-x i insert-file Insert file at cursor position.
C-x k kill-buffer Delete the buffer specified.
C-x o other-window Move to the other window.
C-x q kbd-macro-query Insert a query in a macro definition.
C-x s save-some-buffers Ask whether to save each modified buffer.

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C-x u advertised-undo Undo last edit (can be done repeatedly).
C-y yank Restore what you've deleted.
C-z suspend-emacs Suspend Emacs (use exit or fg to restart).

10.4.2. Meta-Key Sequences
Binding Command Action
M--M-c negative-argument; capitalize-word Capitalize previous word.
M--M-l negative-argument; downcase-word Lowercase previous word.
M--M-u negative-argument; upcase-word Uppercase previous word.
M-$ spell-word Check spelling of word after cursor.
M-< beginning-of-buffer Move to beginning of file.
M-> end-of-buffer Move to end-of-file.
M-{ backward-paragraph Move backward one paragraph.
M-} forward-paragraph Move forward one paragraph.
M-^ delete-indentation Join this line to the previous one.
M-n digit-argument Repeat the next command n times.
M-n C-x e digit-argument; call-last-kbd-macro Execute the last defined macro n times.
M-a backward-sentence Move backward one sentence.
M-b backward-word Move one word backward.
M-c capitalize-word Capitalize first letter of word.

M-C-\ indent-region Indent a region to match first line in region.
M-C-c exit-recursive-edit Exit a recursive edit.
M-C-o split-line Split line at cursor; indent to column of cursor.

M-C-r isearch-backward-regexp Incremental search backward for regular expression.

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M-C-s isearch-forward-regexp Incremental search forward for regular expression.
M-C-v scroll-other-window Scroll other window.
M-d kill-word Delete word that cursor is on.
M-Del backward-kill-word Delete previous word.
M-e forward-sentence Move forward one sentence.
M-f forward-word Move one word forward.

(none) fill-region Reformat individual paragraphs within a region.

M-h mark-paragraph Place cursor and mark around whole paragraph.
M-k kill-sentence Delete sentence the cursor is on.
M-l downcase-word Lowercase word.

M-m back-to-indentation Move cursor to first nonblank character on line.
M-q fill-paragraph Reformat paragraph.
M-t transpose-words Transpose two words.
M-u upcase-word Uppercase word.
M-v scroll-down Move backward one screen.
M-x (none) Execute a command by typing its name.

10.3. Summary of
Commands by Group
10.5. Summary of
Commands by Name

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Linux in a Nutshell, 3rd
Edition

10.5. Summary of Commands by Name
The following Emacs commands are presented alphabetically by command name. Use M-x to
access the command name. Tables list command name, keystroke, and description. C-
indicates the Ctrl key; M-indicates the Meta key.

Command Binding Action
macroname (none) Execute a keyboard macro you've saved.
abbrev-mode (none) Enter (or exit) word abbreviation mode.
abort-recursive-edit C-] Exit recursive edit and exit query-replace.
advertised-undo C-x u Undo last edit (can be done repeatedly).
apropos (none) What functions and variables involve this concept?

back-to-indentation M-m Move cursor to first nonblank character on line.
backward-char C-b Move backward one character (left).
backward-delete-char Del Delete previous character.
backward-kill-paragraph (none) Delete previous paragraph.
backward-kill-sentence C-x Del Delete previous sentence.
backward-kill-word C-c C-w Erase previous word.
backward-kill-word M-Del Delete previous word.
backward-page C-x [ Move backward one page.
backward-paragraph M-{ Move backward one paragraph.

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backward-sentence M-a Move backward one sentence.
backward-word M-b Move backward one word.
beginning-of-buffer M-< Move to beginning of file.
beginning-of-line C-a Move to beginning of line.
call-last-kbd-macro C-x e Execute last macro defined.
capitalize-region (none) Capitalize region.
capitalize-word M-c Capitalize first letter of word.
center-line (none) Center line that cursor is on.
center-paragraph (none) Center paragraph that cursor is on.
center-region (none) Center currently defined region.
command-apropos C-h a What commands involve this concept?

compare-windows (none) Compare two buffers; show first difference.
delete-char C-d Delete character under cursor.
delete-indentation M-^ Join this line to previous one.
delete-other-windows C-x 1 Delete all windows but this one.
delete-window C-x 0 Delete current window.
delete-windows-on (none) Delete all windows on a given buffer.

describe-bindings C-h b What are all the key bindings for in this buffer?

describe-copying C-h C-c View the Emacs General Public License.
describe-distribution C-h C-d View information on ordering Emacs from the FSF.
describe-function C-h f What does this function do?
describe-key C-h k What command does this keystroke sequence run, and what does it do?

describe-key-briefly C-h c What command does this keystroke sequence run?

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describe-mode C-h m Tell me about the mode the current buffer is in.
describe-no-warranty C-h C-w View the (non) warranty for Emacs.
describe-syntax C-h s What is the syntax table for this buffer?

describe-variable C-h v What does this variable mean, and what is its value?
digit-argument M-n Repeat next command n times.
downcase-region C-x C-l Lowercase region.
downcase-word M-l Lowercase word.
edit-abbrevs (none) Edit word abbreviations.
end-kbd-macro C-x ) End macro definition.
end-of-buffer M-> Move to end-of-file.
end-of-line C-e Move to end-of-line.
enlarge-window C-x ^ Make window taller.
enlarge-window-horizontally C-x } Make window wider.
exchange-point-and-mark C-x C-x Exchange location of cursor and mark.
exit-recursive-edit M-C-c Exit a recursive edit.

fill-individual-paragraphs (none) Reformat indented paragraphs, keeping indentation.
fill-paragraph M-q Reformat paragraph.
fill-region (none) Reformat individual paragraphs within a region.

find-alternate-file C-x C-v Read an alternate file, replacing the one currently in the buffer.
find-file C-x C-f Find file and read it.
find-file-other-frame C-x 5 f Find a file in a new frame.
find-file-other-window C-x 4 f Find a file in the other window.
forward-char C-f Move forward one character (right).
forward-page C-x ] Move forward one page.

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forward-paragraph M-} Move forward one paragraph.
forward-sentence M-e Move forward one sentence.
forward-word M-f Move forward one word.
goto-char (none) Go to character n of file.
goto-line (none) Go to line n of file.
help-command C-h Enter the online help system.
help-with-tutorial C-h t Run the Emacs tutorial.

indent-region M-C-\ Indent a region to match first line in region.

indented-text-mode (none) Major mode: each tab defines a new indent for subsequent lines.
info C-h i Start the Info documentation reader.
insert-file C-x i Insert file at cursor position.
insert-last-keyboard-macro (none) Insert the macro you named into a file.
interrupt-shell-subjob C-c C-c Terminate the current job (shell mode).

inverse-add-global-abbrev C-x a -Define previous word as global (mode-independent) abbreviation.

inverse-add-mode-abbrev C-x a i l Define previous word as mode-specific abbreviation.
isearch-backward C-r Start incremental search backward.
isearch-backward-regexp M-C-r Same, but search for regular expression.
isearch-forward C-s Start incremental search forward.
isearch-forward-regexp M-C-s Same, but search for regular expression.
kbd-macro-query C-x q Insert a query in a macro definition.
keyboard-quit C-g Abort current command.
kill-all-abbrevs (none) Kill abbreviations for this session.
kill-buffer C-x k Delete the buffer specified.
kill-line C-k Delete from cursor to end-of-line.

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kill-paragraph (none) Delete from cursor to end of paragraph.
kill-region C-w Delete a marked region.
kill-sentence M-k Delete sentence the cursor is on.
kill-shell-input C-c C-u Erase current line.
kill-some-buffers (none) Ask about deleting each buffer.
kill-word M-d Delete word the cursor is on.
list-abbrevs (none) View word abbreviations.
list-buffers C-x C-b Display buffer list.
load-file (none) Load macro files you've saved.

mark-page C-x C-p Place cursor and mark around whole page.

mark-paragraph M-h Place cursor and mark around whole paragraph.
mark-whole-buffer C-x h Place cursor and mark around whole buffer.
name-last-kbd-macro (none) Name last macro you created (before saving it).
negative-argument; capitalize-word M--M-c Capitalize previous word.

negative-argument; downcase-word M--M-l Lowercase previous word.
negative-argument; upcase-word M--M-u Uppercase previous word.
next-line C-n Move to next line (down).
other-window C-x o Move to the other window.
previous-line C-p Move to previous line (up).
query-replace-regexp (none) Query-replace a regular expression.

quoted-insert C-q Insert next character typed. Useful for inserting a control character.

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recenter C-l Redraw screen, with current line in center.
rename-buffer (none) Change buffer name to specified name.
replace-regexp (none) Replace a regular expression unconditionally.

re-search-backward (none) Simple regular-expression search backward.
re-search-forward (none) Simple regular-expression search forward.

revert-buffer (none)
Restore buffer to the state it was in
when the file was last saved (or auto-saved).

save-buffer C-x C-s Save file. (If terminal hangs, C-q restarts.)
save-buffers-kill-emacs C-x C-c Exit Emacs.
save-some-buffers C-x s Ask whether to save each modified buffer.
scroll-down M-v Move backward one screen.
scroll-left C-x < Scroll the window left.
scroll-other-window M-C-v Scroll other window.
scroll-right C-x > Scroll the window right.
scroll-up C-v Move forward one screen.

set-fill-prefix C-x .
Prepend each line in paragraph with
characters from beginning of line up to
cursor column; cancel prefix by typing
this command in column 1.

set-mark-command C-@ or C-Space Mark the beginning (or end) of a region.
shell-send-eof C-c C-d End-of-file character (shell mode).
shrink-window (none) Make window shorter.
shrink-window-horizontally C-x { Make window narrower.
spell-buffer (none) Check spelling of current buffer.

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spell-region (none) Check spelling of current region.

spell-string (none) Check spelling of string typed in minibuffer.
spell-word M-$ Check spelling of word after cursor.
split-line M-C-o Split line at cursor; indent to column of cursor.

split-window-horizontally C-x 3 Divide current window horizontally into two.
split-window-vertically C-x 2 Divide current window vertically into two.
start-kbd-macro C-x ( Start macro definition.
stop-shell-subjob C-c C-z Suspend current job.
suspend-emacs C-z Suspend Emacs (use fg to restart).
switch-to-buffer C-x b Move to the buffer specified.
switch-to-buffer-other-frame C-x 5 b Select a buffer in another frame.
switch-to-buffer-other-
window C-x 4 b Select a buffer in the other window.

text-mode (none) Enter text mode.
transpose-chars C-t Transpose two letters.
transpose-lines C-x C-t Transpose two lines.
transpose-paragraphs (none) Transpose two paragraphs.
transpose-sentences (none) Transpose two sentences.
transpose-words M-t Transpose two words.
unexpand-abbrev (none) Undo the last word abbreviation.
universal-argument C-u n Repeat the next command n times.
upcase-region C-x C-u Uppercase region.
upcase-word M-u Uppercase word.
view-emacs-news C-h n View news about updates to Emacs.

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view-lossage C-h l What are the last 100 characters I typed?

where-is C-h w What is the key binding for this command?
write-abbrev-file (none) Write the word abbreviation file.
write-file C-x C-w Write buffer contents to file.
yank C-y Restore what you've deleted.

10.4. Summary of
Commands by Key
11. The vi Editor

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The vi Editor (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

Chapter 11. The vi Editor
Contents:
Review of vi Operations
vi Command-Line Options
ex Command-Line Options
Movement Commands
Edit Commands
Saving and Exiting
Accessing Multiple Files
Interacting with the Shell
Macros
Miscellaneous Commands
Alphabetical List of Keys in Command Mode
Syntax of ex Commands
Alphabetical Summary of ex Commands
vi Configuration

vi is the classic screen-editing program for Unix. A number of enhanced versions exist,
including nvi, vim, vile, and elvis. On Linux, the vi command is usually a link to one of these
programs.

vi is based on an older line editor called ex. Powerful editing capabilities can be invoked
within vi by pressing the colon (:), entering an ex command, and pressing the Return key.
Furthermore, you can place ex commands in a startup file called ~/. exrc, which vi reads at the
beginning of your editing session. Because ex commands are still an important part of vi, they
also are described in this chapter. On Linux, ex is sometimes called hex.

This chapter, which essentially covers standard vi but reflects nvi extensions, presents the
following topics:

l Review of vi operations

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l vi command-line options

l ex command-line options
l Movement commands
l Edit commands
l Saving and exiting
l Accessing multiple files
l Interacting with the shell
l Macros
l Miscellaneous commands
l Alphabetical list of keys in command mode
l Syntax of ex commands
l Alphabetical summary of ex commands
l vi configuration (setting options at startup)

For more information, see the O'Reilly book Learning the vi Editor by Linda Lamb and
Arnold Robbins.

11.1. Review of vi Operations
This section provides a review of the following:
l Command-line options

l vi modes
l Syntax of vi commands
l Status-line commands

11.1.1. Command Mode
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Once the file is opened, you are in command mode. From command mode, you can:
l Invoke insert mode

l Issue editing commands
l Move the cursor to a different position in the file
l Invoke ex commands
l Invoke a Linux shell
l Save or exit the current version of the file

11.1.2. Insert Mode
In insert mode, you can enter new text in the file. Press the Esc or Ctrl-[ keys to exit insert
mode and return to command mode. The following commands invoke insert mode:

aAppend after cursor
AAppend at end-of-line
cBegin change operation (must be followed by a movement command)
CChange to end-of-line
iInsert before cursor
IInsert at beginning of line

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oOpen a line below current line
OOpen a line above current line
RBegin overwriting text
sSubstitute a character
SSubstitute entire line

11.1.3. Syntax of vi Commands
In vi, commands have the following general form:
[n] operator [m] objectThe basic editing operators are:
cBegin a change
dBegin a deletion
yBegin a yank (or copy)
If the current line is the object of the operation, then the operator is the same as the object: cc,
dd, yy. Otherwise, the editing operators act on objects specified by cursor-movement
commands or pattern-matching commands. n and m are the number of times the operation is

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performed or the number of objects the operation is performed on. If both n and m are
specified, the effect is n � m.

An object can represent any of the following text blocks:
word
Includes characters up to a space or punctuation mark. A capitalized object is a variant
form that recognizes only blank spaces.

sentence
Extends to ., !, ? followed by two spaces.
paragraph
Extends to next blank line or nroff/ troff paragraph macro (defined by para= option).
section
Extends to next nroff/ troff section heading (defined by sect= option).

11.1.3.1. Examples
2cwChange the next two words
d}Delete up to next paragraph
d^Delete back to beginning of line
5yyCopy the next five lines into temporary buffer (for future pasting)
y]]Copy up to the next section into temporary buffer (for future pasting)

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11.1.4. Status-Line Commands
Most commands are not echoed on the screen as you input them. However, the status line at
the bottom of the screen is used to echo input for the following commands:

/Search forward for a pattern
?Search backward for a pattern
:Invoke an ex command
!Pipe the text indicated by a subsequent movement command through the following
shell command, and replace the text with the output of the shell command

Commands that are input on the status line must be entered by pressing the Return key. In
addition, error messages and output from the Ctrl-G command are displayed on the status
line.

10.5. Summary of
Commands by Name
11.2. vi Command-Line
Options

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11.2. vi Command-Line Options
The three most common ways of starting a vi session are:
vi filevi + n filevi +/ pattern file

You can open file for editing, optionally at line n or at the first line matching pattern. If no file
is specified, vi opens with an empty buffer. The command-line options that can be used with
vi are:

+[ num]
Start editing at line number num, or the last line of the file if num is omitted.
+/ pattern
Start editing at the first line matching pattern. (Fails if nowrapscan is set in your .exrc
startup file.)

-c command
Run the given vi command upon startup. Only one -c option is permitted. ex
commands can be invoked by prefixing them with a :. An older form of this option,
+command, is still supported.

-e
Run as ex (line editing rather than full-screen mode).
-l
Enter LISP mode for running LISP programs (not supported in all versions).

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-r [file]

Recover and resume editing on file after an aborted editor session or system crash.
Without file, list files available for recovery.

-t tag
Edit the file containing tag and position the cursor at its definition (see ctags in
Chapter 3, "Linux Commands" for more information).

-v

Run in full-screen mode (default).
-w rows

Set the window size so rows lines at a time are displayed; useful when editing over a
slow dial-up line.
-x

Prompt for a key that will be used to try to encrypt or decrypt a file using crypt (not
supported in all versions).
-C

Same as -x, but assume the file is encrypted already (not supported in all versions).
-L

List files that were saved due to an aborted editor session or system crash (not
supported in all versions).
-R

Edit files read-only.

11. The vi Editor 11.3. ex Command-Line
Options

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11.3. ex Command-Line Options
While most people know ex commands only by their use within vi, the editor exists also as a
separate program and can be invoked from the shell (for instance, to edit files as part of a
script). Within ex, you can enter the vi or visual command to start vi. Similarly, within vi, you
can enter Q to quit the vi editor and enter ex.

If you invoke ex as a standalone editor, you can include the following options:
+[ num]
Start editing at line number num, or the last line of the file if num is omitted.
+/ pattern
Start editing at the first line matching pattern. (Fails if nowrapscan is set in your .exrc
start-up file.)

-c command
Run the given ex command upon start-up. Only one -c option is permitted. An older
form of this option, +command, is still supported.

-e
Run as a line editor rather than full-screen vi mode (default).
-l
Enter LISP mode for running LISP programs (not supported in all versions).
-r [file]
Recover and resume editing on file after an aborted editor session or system crash.

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Without file, list files available for recovery.

-s
Silent; do not display prompts. Useful when running a script. This behavior also can be
set through the older -option.

-t tag
Edit the file containing tag and position the cursor at its definition (see ctags in
Chapter 3, "Linux Commands" for more information).

-v

Run in full-screen mode (same as invoking vi).
-w rows

Set the window size so rows lines at a time are displayed; useful when editing by a
slow dial-up line.
-x

Prompt for a key that will be used to try to encrypt or decrypt a file using crypt (not
supported in all versions).
-C

Same as -x, but assume the file is encrypted already (not supported in all versions).
-L

List files that were saved due to an editor of system crash (not supported in all
versions).
-R

Edit files read-only; do not allow changes to be saved.
You can exit ex in several ways:
:xExit (save changes and quit).
:q!Quit without saving changes.
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Enter the vi editor.

11.2. vi Command-Line
Options
11.4. Movement Commands

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11.4. Movement Commands
A number preceding a command repeats the movement. Movement commands are also
objects for change, delete, and yank operations.

11.4.1. Character

Command Action
h, j, k, l Left, down, up, right ( , , , )
Spacebar Right
Backspace Left
Ctrl-H Left

11.4.2. Text
Command Action
w, b Forward, backward by word (treating punctuation marks as words).

W, B Forward, backward by word (recognizing only whitespace, not punctuation, as separators).
e End of word (treating a punctuation mark as the end of a word).
E End of word (recognizing only whitespace as the end of a word).
), ( Beginning of next, current sentence.
}, { Beginning of next, current paragraph.
]], [[ Beginning of next, current section.

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Ctrl-D Move to previous tab setting.
Ctrl-T Move to next tab setting.
Ctrl-W Move back one word.

11.4.3. Lines
Command Action
0, $ First, last position of current line.
^, _ First nonblank character of current line.
+, -First character of next, previous line.
Return First nonblank character of next line.
n| Column n of current line.
H Top line of screen.
M Middle line of screen.
L Last line of screen.
nH n lines after top line.
nL n lines before last line.
Ctrl-J Move down one line.
Ctrl-M Move to first nonblank character of next line.

11.4.4. Screens
Command Action
Ctrl-F, Ctrl-B Scroll forward, backward one screen.
Ctrl-D, Ctrl-U Scroll down, up one-half screen.
Ctrl-E, Ctrl-Y Show one more line at bottom, top of window.
z Return Reposition line with cursor to top of screen.
z. Reposition line with cursor to middle of screen.

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z-Reposition line with cursor to bottom of screen.
Ctrl-L, Ctrl-R Redraw screen (without scrolling).

11.4.5. Searches
Command Action
/pattern Search forward for pattern.
/ Repeat previous search forward.
/pattern/+ n Go to line n after pattern.
?pattern Search backward for pattern.
? Repeat previous search backward.
?pattern?-n Go to line n before pattern.
n Repeat previous search.
N Repeat previous search in opposite direction.
% Find match of current parenthesis, brace, or bracket.
fx Move forward to x on current line.
Fx Move backward to x on current line.
tx Move forward to just before x in current line.
Tx Move back to just after x in current line.
, Reverse search direction of last f, F, t, or T.
; Repeat last character search (f, F, t, or T).

11.4.5.1. Line numbering
Command Action
Ctrl-G Display current filename and line number.
nG Move to line number n.
G Move to last line in file.

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:n Move to line number n.

11.4.5.2. Marking position
Command Action
mx Mark current position with character x.
`x (backquote) Move cursor to mark x.
'x (apostrophe) Move to start of line containing x.
`` (backquotes) Return to previous mark (or location prior to search).
'' (apostrophes) Like preceding, but return to start of line.

11.3. ex Command-Line
Options
11.5. Edit Commands

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11.5. Edit Commands
Recall that c, d, and y are the basic editing operators.

11.5.1. Inserting New Text

Command Action
a Append after cursor.
A Append to end of line.
i Insert before cursor.
I Insert at beginning of line.
o Open a line below cursor.
O Open a line above cursor.
Esc Terminate insert mode.
Tab Insert a tab.
Backspace Delete previous character (in insert mode).
Ctrl-I Insert a tab.
Ctrl-U Delete current line.
Ctrl-V Insert next character verbatim.
Ctrl-[ Terminate insert mode.

Some of the control characters listed in the previous table are set by stty. Your terminal
settings may differ.

11.5.2. Changing and Deleting Text
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Edit Commands (Linux in a Nutshell, 3rd Edition)
The following table is not exhaustive but illustrates the most common operations.
Command Action
cw Change through end of current word.
cc Change line.
c$ Change text from current position to end-of-line.
C Same as c$.
dd Delete current line.
d$ Delete remainder of line.
D Same as d$.
ndd Delete n lines.
dw Delete a word.
d} Delete up to next paragraph.
d^ Delete back to beginning of line.
d/ pattern Delete up to first occurrence of pattern.
dn Delete up to next occurrence of pattern.
dfa Delete up to and including a on current line.
dta Delete up to (not including) a on current line.
dL Delete up to last line on screen.
dG Delete to end-of-file.
p Insert last deleted text after cursor.
P Insert last deleted text before cursor.
rx Replace character with x.
Rtext Replace text beginning at cursor.
s Substitute character.
ns Substitute n characters.
S Substitute entire line.

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u Undo last change.
U Restore current line.
x Delete current character.
X Delete back one character.
nX Delete previous n characters.
. Repeat last change.
~ Reverse case.
& Repeat last substitution.
Y Copy (yank) current line to temporary buffer.
yy Same as Y.
"xyy Copy current line to buffer x.
ye Copy text to end of word into temporary buffer.
yw Same as ye.
y$ Copy rest of line into temporary buffer.
"xdd Delete current line into buffer x.
"Xdd Delete current line and append to buffer x.
"xp Put contents of buffer x.
J Join previous line to current line.
:j! Same as J.

11.4. Movement Commands 11.6. Saving and Exiting
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Linux in a Nutshell, 3rd
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11.6. Saving and Exiting
Writing a file means saving the edits and updating the file's modification time.

Command Action
ZZ Quit vi, writing the file only if changes were made.
:x Same as ZZ.
:wq Write and quit file.
:w Write file.
:w file Save copy to file.
:n1, n2w file Write lines n1 to n2 to new file.
:n1, n2w >> file Append lines n1 to n2 to existing file.
:w! Write file (overriding protection).
:w! file Overwrite file with current buffer.
:w %. new Write current buffer named file as file. new.
:q Quit file.
:q! Quit file (discarding edits).
Q Quit vi and invoke ex.
:vi Return to vi after Q command.
% Current filename.
# Alternate filename.

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Saving and Exiting (Linux in a Nutshell, 3rd Edition)
11.5. Edit Commands 11.7. Accessing Multiple
Files

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Accessing Multiple Files (Linux in a Nutshell, 3rd Edition)
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11.7. Accessing Multiple Files
Command Action
:e file Edit another file; current file becomes alternate.
:e! Restore last saved version of current file.
:e+ file Begin editing at end of new file.
:e+ n file Open new file at line n.
:e# Open to previous position in alternate file.
:ta tag Edit file containing tag at the location of the tag.
:n Edit next file.
:n! Force next file into buffer (don't save changes to current file).
:n files Specify new list of files.
:args Display multiple files to be edited.
:rew Rewind list of multiple files to top.

11.6. Saving and Exiting 11.8. Interacting with the
Shell

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11.8. Interacting with the Shell
Command Action
:r file Read in contents of file after cursor.
:r !command Read in output from command after current line.
:nr !command Like preceding, but place after line n (0 for top of file).
:! command Run command, then return.

!object command Send object, indicated by a movement command, as input to shell command command; replace object with command output.
:n1, n2! command Send lines n1 through n2 to command; replace with output.
n!! command Send n lines to command; replace with output.
!! Repeat last system command.
!! command Replace current line with output of command.
:sh Create subshell; return to file with EOF.
Ctrl-Z Suspend editor, resume with fg.
:so file Read and execute ex commands from file.

11.7. Accessing Multiple
Files
11.9. Macros

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11.9. Macros
Command Action
:ab in out Use in as abbreviation for out.
:unab in Remove abbreviation for in.
:ab List abbreviations.
:map c sequence Map character c as sequence of commands.
:unmap c Disable map for character c.
:map List characters that are mapped.
:map! c sequence Map character c to input mode sequence.

:unmap! c Disable input mode map (you may need to quote the character with Ctrl-V).
:map! List characters that are mapped to input mode.

The following characters are unused in command mode and can be mapped as user-defined
commands:

Letters:
g K q V v
Control keys:
^K ^O ^T ^W ^X
Symbols:
_ * \ =
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Macros (Linux in a Nutshell, 3rd Edition)
NOTE
The = is used by vi if LISP mode is set. Different versions of vi may use some
of these characters, so test them before using them.

11.8. Interacting with the
Shell
11.10. Miscellaneous
Commands

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11.10. Miscellaneous Commands
Command Action
< Shift line left to position indicated by following movement command.
> Shift line right to position indicated by following movement command.
<< Shift line left one shift width (default is 8 spaces).
>> Shift line right one shift width (default is 8 spaces).
>} Shift right to end of paragraph.

<% Shift left until matching parenthesis, brace, bracket, etc. (Cursor must be on the matching symbol.)
^[ Abort command or end input mode.
^] Perform a tag look-up on the text under the cursor.
^\ Enter ex line-editing mode.
^^ (Caret key with Ctrl key pressed) Return to previously edited file.

11.9. Macros 11.11. Alphabetical List of
Keys in Command Mode

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11.11. Alphabetical List of Keys in Command
Mode

For brevity, control characters are marked by ^.

Command Action
a Append text after cursor.
A Append text at end-of-line.
^A Search for next occurrence of word under cursor.
b Back up to beginning of word in current line.
B Back up one word, treating punctuation marks as words.
^B Scroll backward one window.
c Change text up to target of next movement command.
C Change to end of current line.
^C End insert mode; interrupts a long operation.
d Delete up to target of next movement command.
D Delete to end of current line.

^D Scroll down half-window; in insert mode, unindent to shiftwidth if autoindent is set.
e Move to end of word.
E Move to end of word, treating punctuation as part of word.
^E Show one more line at bottom of window.
f Find next character typed forward on current line.

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Alphabetical List of Keys in Command Mode (Linux in a Nutshell, 3rd Edition)
F Find next character typed backward on current line.
^F Scroll forward one window.
g Unused.
G Go to specified line or end-of-file.
^G Print information about file on status line.
h Left arrow cursor key.
H Move cursor to home position.
^H Left arrow cursor key; Backspace key in insert mode.
i Insert text before cursor.
I Insert text before first nonblank character on line.
^I Unused in command mode; in insert mode, same as Tab key.
j Down arrow cursor key.
J Join previous line to current line.
^J Down arrow cursor key; in insert mode, move down a line.
k Up arrow cursor key.
K Unused.
^K Unused.
l Right arrow cursor key.
L Move cursor to last position in window.
^L Redraw screen.
m Mark the current cursor position in register (a-z).
M Move cursor to middle position in window.
^M Move to beginning of next line.
n Repeat the last search command.
N Repeat the last search command in reverse direction.
^N Down arrow cursor key.
o Open line below current line.

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O Open line above current line.
^O Unused.
p Put yanked or deleted text after or below cursor.
P Put yanked or deleted text before or above cursor.
^P Up arrow cursor key.
q Unused.
Q Quit vi and enter ex line-editing mode.
^Q Unused. (On some terminals, resume data flow.)
r Replace character at cursor with the next character you type.
R Replace characters.
^R Redraw the screen.
s Change the character under the cursor to typed characters.
S Change entire line.
^S Unused. (On some terminals, stop data flow.)

t Find next character typed forward on current line and position cursor before it.

T Find next character typed backward on current line and position cursor after it.
^T Unused in command mode; in insert mode, move to next tab setting.
u Undo the last change made.
U Restore current line, discarding changes.
^U Scroll the screen upward a half-window.
v Unused.
V Unused.
^V Unused in command mode; in insert mode, insert next character verbatim.
w Move to beginning of next word.
W Move to beginning of next word, treating punctuation marks as words.

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^W Unused in command mode; in insert mode, back up to beginning of word.
x Delete character under cursor.
X Delete character before cursor.
^X Unused.

y Yank or copy text up to target of following movement command into temporary buffer.
Y Make copy of current line.
^Y Show one more line at top of window.

zReposition line containing cursor. z must be followed by Return (reposition
line to top of screen), . (reposition line to middle of screen), or -(reposition
line to bottom of screen).

ZZ Exit the editor, saving changes.

11.10. Miscellaneous
Commands
11.12. Syntax of ex
Commands

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11.12. Syntax of ex Commands
To enter an ex command from vi, type:
:[ address] command [options]An initial : indicates an ex command. As you type the command, it is echoed on the status
line. Enter the command by pressing Return. address is the line number or range of lines that
are the object of command. options and addresses are described in the following sections. ex
commands are described in the alphabetical summary.

11.12.1. Options
!
Indicates a variant command form, overriding the normal behavior.
count
The number of times the command is to be repeated. Unlike vi commands, ex
commands cannot be preceded by count, because a number preceding an ex command
is treated as a line address. For example, d3 deletes 3 lines beginning with the current
line; 3d deletes line 3.

file
The name of a file that is affected by the command. %stands for current file; # stands
for previous file.

11.12.2. Addresses
If no address is given, the current line is the object of the command. If the address specifies a
range of lines, the format is:

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x, ywhere x and y are the first and last addressed lines (x must precede y in the buffer). x and y
may be line numbers or symbols. Using ; instead of , sets the current line to x before
interpreting y. The notation 1,$ addresses all lines in the file, as does %.

11.12.3. Address Symbols

Symbol Meaning
1,$ All lines in the file
% All lines; same as 1,$
x, y Lines x through y
x; y Lines x through y, with current line reset to x
0 Top of file
. Current line
n Absolute line number n
$ Last line
x-n n lines before x
x+ n n lines after x
-[ n] One or n lines previous
+[ n] One or n lines ahead
'x Line marked with x
'' Previous mark
/pattern/ Forward to line matching pattern
?pattern? Backward to line matching pattern

See Chapter 9, "Pattern Matching", for more information on using patterns.

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11.11. Alphabetical List of
Keys in Command Mode
11.13. Alphabetical
Summary of ex Commands

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11.13. Alphabetical Summary of ex Commands
ex commands can be entered by specifying any unique abbreviation. In this listing, the full name appears in the margin, and the shortest possible abbreviation
is used in the syntax line. Examples are assumed to be typed from vi, so they include the : prompt.

abbrev ab [string text]
Define string when typed to be translated into text. If string and text are not specified, list all current abbreviations.
Examples
Note: ^M appears when you type Ctrl-V followed by Return.
:ab ora O'Reilly & Associates, Inc.:ab id Name:^ MRank:^ MPhone:

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append [address] a[!]
text
.
Append text at specified address, or at present address if none is specified. Add a ! to switch the autoindent setting that will be used during
input (e. g., if autoindent was enabled, ! disables it). Terminate input by entering a line consisting of just a period.

args ar
Print filename arguments (the list of files to edit). The current argument is shown in brackets ([]).

cd cd dir
chdir dir
Change current directory within the editor to dir.

change [address] c[!]
text
.
Replace the specified lines with text. Add a ! to switch the autoindent setting during input of text. Terminate input by entering a line
consisting of just a period.

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copy [address] co destination
Copy the lines included in address to the specified destination address. The command t is the same as copy.
Example

:1,10 co 50 Copy first 10 lines to just after line 50delete [address] d [buffer]
Delete the lines included in address. If buffer is specified, save or append the text to the named buffer.
Examples
:/ Part I/,/ Part II/-1d Delete to line above "Part II" :/main/+ d Delete line below "main" :.,$d Delete from this line to last line

edit e[!] [+ n] [file]
Begin editing file. Add a ! to discard any changes to the current file. If no file is given, edit another copy of the current file. With the +n
argument, begin editing on linen.

Examples

:e file:e# Return to editing the previous file :e! Discard edits since last save

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exusage exu [command]
Print a brief usage message describing command, or a list of available commands if command is omitted.

file f [filename]
Change the name of the current file to filename, which is considered "not edited." If no filename is specified, print the current status of the
file.

Example
:f %. new

global [address] g[!]/ pattern<//[ commands]
Execute commands on all lines that contain pattern or, if address is specified, on all lines within that range. If commands are not specified,
print all such lines. If ! is used, execute commands on all lines that don't contain pattern. See v.

Examples
:g/ Unix/ p Print all lines containing "Unix" :g/Name:/ s/ tom/ Tom/ Change "tom" to "Tom" on all lines containing "Name:"

help h
Print a brief help message. Information on particular commands can be obtained through the exusage and viusage commands.

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insert address i[!]
text
.
Insert text at line before the specified address, or at present address if none is specified. Add a ! to switch the autoindent setting during
input of text. Terminate input by entering a line consisting of just a period.

join [address] j[!] [count]
Place the text in the specified address on one line, with whitespace adjusted to provide two blank characters after a period (.), no blank
characters after a ), and one blank character otherwise. Add a ! to prevent whitespace adjustment.

Example

:1,5j! Join first five lines, preserving whitespacek [address] k char
Mark the given address with char. Return later to the line with 'char.

list [address] l [count]
Print the specified lines so that tabs display as ^I, and the ends of lines display as $. l is a temporary version of :set list.

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map map[!] [char commands]
Define a keyboard macro named char as the specified sequence of commands. char is usually a single character, or the sequence #n,
representing a function key on the keyboard. Use a ! to create a macro for input mode. With no arguments, list the currently defined macros.

Examples
:map K dwwP Transpose two words :mapq :w^ M: n^ M Write current file; go to next :map!+ ^[ bi(^[ ea) Enclose previous word in parentheses

mark [address] ma char
Mark the specified line with char, a single lowercase letter. Return later to the line with 'char. Same as k.

mkexrc mk[!] file
Create an .exrc file containing a set command for every ex option, set to defaults.

move [address] m destination
Move the lines specified by address to the destination address.
Example

:.,/ Note/ m /END/ Move text block after line containing "END"

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next n[!] [[+ command] filelist]
Edit the next file from the command-line argument list. Use args to list these files. If filelist is provided, replace the current argument list
with filelist and begin editing on the first file; if command is given (containing no spaces), execute command after editing the first such file.
Add a ! to discard any changes to the current file.

Example

:n chap* Start editing all "chapter" filesnumber [address] nu [count]
Print each line specified by address, preceded by its buffer line number. Use # as an alternate abbreviation for number. count specifies the
number of lines to show, starting with address.

open [address] o [/ pattern/]
Enter vi's open mode at the lines specified by address or at the lines matching pattern. Enter and exit open mode with Q. Open mode lets
you use the regular vi commands, but only one line at a time. May be useful on slow dial-up lines.

preserve pre
Save the current editor buffer as though the system had crashed.

previous prev[!]
Edit the previous file from the command-line argument list.

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print [address] p [count]
[address] P [count]
Print the lines specified by address. count specifies the number of lines to print, starting with address. Add a ! to discard any changes to the
current file.

Example

:100;+ 5p Show line 100 and the next 5 linesput [address] pu [char]
Restore the lines that were previously deleted or yanked from named buffer char, and put them after the line specified by address. If char is
not specified, restore the last deleted or yanked text.

quit q[!]
Terminate current editing session. Use ! to discard changes made since the last save. If the editing session includes additional files in the
argument list that were never accessed, quit by typing q! or by typing q twice.

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read [address] r file
Copy in the text from file on the line below the specified address. If file is not specified, the current filename is used.
Example

:0r $HOME/ data Read file in at top of current fileread [address] r !command
Read the output of Linux command into the text after the line specified by address.
Example

:$ r !cal Place a calendar at end-of-filerecover rec [file]
Recover file from system save area.

rewind rew[!]
Rewind argument list and begin editing the first file in the list. The ! flag rewinds, discarding any changes to the current file that haven't
been saved.

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script sc[!] [file]
Create a new shell in a buffer that can be saved, optionally specifying file where the buffer can be saved. Can be used only in vi.

set se parameter1 parameter2 ...
Set a value to an option with each parameter, or if no parameter is supplied, print all options that have been changed from their defaults.
For Boolean-valued options, each parameter can be phrased as option or nooption; other options can be assigned with the syntax
option= value. Specify all to list current settings.

Examples
:set nows wm= 10:set all

shell sh
Create a new shell. Resume editing when the shell is terminated.

source so file
Read and execute ex commands from file.
Example
:so $HOME/. exrc

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stop st
Suspend the editing session. Same as Ctrl-Z. Use fg to resume session.

substitute [address] s [/ pattern/ replacement/] [options] [count]
Replace each instance of pattern on the specified lines with replacement. If pattern and replacement are omitted, repeat last substitution.
count specifies the number of lines on which to substitute, starting with address. When preceded by the global (g) or v command, this
command can be specified with a blank pattern, in which case the pattern from the g or v command is then used. For more examples, see
Section 9.4.1, "Examples of Searching and Replacing" in Chapter 9, "Pattern Matching".

Options
c
Prompt for confirmation before each change.
g

Substitute all instances of pattern on each line.
p

Print the last line on which a substitution was made.
Examples
:1,10s/ yes/ no/ g Substitute on first 10 lines :%s/[ Hh] ello/ Hi/ gc Confirm global substitutions :s/Fortran/\ U&/ 3 Uppercase first instance of "Fortran" on next three lines :g/^[0-9][ 0-9]*/ s// Line &:/ For every line beginning with one or more digits, add the "Line" and a colon

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suspend su
Suspend the editing session. Same as Ctrl-Z. Use fg to resume session.

t [address] t destination
Copy the lines included in address to the specified destination address. t is an alias for copy.
Example

:% t$ Copy the file and add it to the endtag [address] ta[!] tag
Switch the editing session to the file containing tag.
Example
Run ctags, then switch to the file containing myfunction:
:! ctags *. c:tag myfunction

tagnext tagn[!]
Find the next occurrence of the current tag.

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tagpop tagp[!]
Forget the current tag and return to the last position of the previous tag found.

tagprev tagpr[!]
Return to the previous occurrence of the current tag.

tagtop tagt[!]
Return to the first tag searched for and forget about all tags.

unabbreviate una word
Remove word from the list of abbreviations.

undo u
Reverse the changes made by the last editing command.

unmap unm[!] char
Remove char from the list of keyboard macros. Use ! to remove a macro for input mode.

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v [address] v/ pattern/[ commands]
Execute commands on all lines not containing pattern. If commands are not specified, print all such lines. v is equivalent to g!. See global.
Example

:v/# include/ d Delete all lines except "# include" linesversion ve
Print the editor's current version number.

vi vi [+ n] file
Begin editing file, optionally at line n. Can be used only in vi.

visual [address] vi [type] [count]
Enter visual mode (vi) at the line specified by address. Exit with Q. type can be one of -, ^, or . (See the z command.) count specifies an
initial window size.

viusage viu [key]
Print a brief usage message describing the operation of key, or a list of defined keys if key is omitted.

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wq wq[!]
Write and quit the file in one command. The ! flag forces the editor to write over any current contents of file.

write [address] w[!] [[>>] file
Write lines specified by address to file, or write full contents of buffer if address is not specified. If file also is omitted, save the contents of
the buffer to the current filename. If >> file is used, write contents to the end of an existing file. The ! flag forces the editor to write over any
current contents of file.

write [address] w !command
Write lines specified by address to command.
Examples
:1,10w name_ list Copy first 10 lines to name_ list :50w>> name_ list Now append line 50

xit x
Write the file if it was changed since the last write, then quit.

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yank [address] ya [char] [count]
Place lines specified by address in named buffer char. If no char is given, place lines in general buffer. count specifies the number of lines
to yank, starting with address.

Example
:101,200 ya a

z [address] z [type] [count]
Print a window of text, with the line specified by address at the top. count specifies the number of lines to be displayed.
Type
+
Place specified line at top of window (the default).
-Place
specified line at bottom of window.
.
Place specified line in center of window.
^
Move up one window.
=
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Place specified line in center of window, and leave this line as the current line.
! [address] !command
Execute Linux command in a shell. If address is specified, apply the lines contained in address as standard input to command, and replace
the lines with the output.

Examples
:! ls List files in the current directory :11,20!sort -f Sort lines 11-20 of current file

= [address] =
Print the line number of the next line matching address. If no address is given, print the number of the last line.

< > [address]<[ count]
[address]>[ count]
Shift lines specified by address either left (<) or right (>). Only blanks and tabs are removed in a left shift. count specifies the number of
lines to shift, starting with address.

address address
Print the line specified in address.

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Return Return
Print the next line in the file.

& & [options] [count]
Repeat the previous substitution (s) command. count specifies the number of lines on which to substitute, starting with address.
Examples
:s/ Overdue/ Paid/ Substitute once on current line :g/Status/& Redo substitution on all "Status" lines

~ [address] ~ [count]
Replace the previous regular expression with the previous replacement pattern from a substitute (s) command.

^D ^DScroll through the file.

^Z ^ZSuspend the editing session. Use fg to resume session.

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Alphabetical Summary of ex Commands (Linux in a Nutshell, 3rd Edition)
11.12. Syntax of ex
Commands
11.14. vi Configuration

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vi Configuration (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

11.14. vi Configuration
This section describes the following:
l The :set command

l Options available with :set
l Sample ~/. exrc file

11.14.1. The :set Command
The :set command lets you specify options that change characteristics of your editing
environment. Options may be put in the ~/. exrc file or set during a vi session.

The colon should not be typed if the command is put in ~/. exrc.

Command Action
:set x Enable option x.
:set nox Disable option x.
:set x= val Give value to option x.
:set Show changed options.
:set all Show all options.
:set x? Show value of option x.

11.14.2. Options Used by :set
The following table describes the options to :set. The first column includes the optional
abbreviation, if there is one, and uses an equals sign to show that the option takes a value. The

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vi Configuration (Linux in a Nutshell, 3rd Edition)
second column gives the default, and the third column describes the behavior of the enabled
option.

Option Default Description
autoindent

(ai)
noai In insert mode, indent each line to the same level as the line above or below. Use with shiftwidth option.

autoprint
(ap)
ap Display changes after each editor command. (For global replacement, display last replacement.)

autowrite
(aw)
noaw
Automatically write (save) file if changed, before
opening another file with :n or before giving Linux
command with :!.

beautify

(bf)
nobf Ignore all control characters during input (except tab, newline, or formfeed).

directory=
(dir)
/tmp Name the directory in which ex stores buffer files. (Directory must be writable.)

edcompatible noed-compatible Use ed-like features on substitute commands.
errorbells

(eb)
errorbells Sound bell when an error occurs.

exrc
(ex)
noexrc Allow the execution of ~/. exrc files that reside outside the user's home directory.

hardtabs=
(ht)
8 Define boundaries for terminal hardware tabs.

ignorecase
(ic)
noic Disregard case during a search.

lisp nolisp Insert indents in appropriate LISP format. (), { }, [[, and ]] are modified to have meaning for LISP.

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vi Configuration (Linux in a Nutshell, 3rd Edition)
list nolist Print tabs as ^I; mark ends of lines with $. (Use list to tell if end character is a tab or a space.)

magic magic Wildcard characters . (dot), * (asterisk), and [ ] (brackets) have special meaning in patterns.
mesg mesg Permit system messages to display on terminal while editing in vi.
number
(nu)
nonu Display line numbers on left of screen during editing session.

redraw
(re)
noredraw

Terminal redraws screen whenever edits are made (in
other words, insert mode pushes over existing
characters, and deleted lines immediately close up).
Default depends on line speed and terminal type.
noredraw is useful at slow speeds on a dumb
terminal: deleted lines show up as @, and inserted text
appears to overwrite existing text until you press Esc.

remap remap Allow nested map sequences.

report= 5
Display a message on the prompt line whenever you
make an edit that affects at least a certain number of
lines. For example, 6dd reports the message "6 lines
deleted."

scroll= <1/ 2 window> Amount of screen to scroll.
sections=

(sect)
SHNHH HU
Define section delimiters for [[ ]] movement. The
pairs of characters in the value are the names of
nroff/ troff macros that begin sections.

shell=

(sh)
/bin/ sh
Pathname of shell used for shell escape (:!) and shell
command (: sh). Default value is derived from SHELL
variable.

shiftwidth=

(sw)
8 Define number of spaces used by the indent commands (^ T, ^D, >>, and <<).

showmatch
(sm)
nosm

In vi, when ) or } is entered, cursor moves briefly to
matching ( or {. (If the match is not on the screen,
rings the error message bell.) Very useful for
programming.

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vi Configuration (Linux in a Nutshell, 3rd Edition)
showmode noshowmode
In insert mode, displays a message on the prompt line
indicating the type of insert you are making, such as
"Open Mode" or "Append Mode."

slowopen

(slow)
Hold off display during insert. Default depends on line
speed and terminal type.

tabstop=
(ts)
8 Define number of spaces that a tab indents during editing session. (Printer still uses system tab of 8.)

taglength=
(tl)
0
Define number of characters that are significant for
tags. Default (0) means that all characters are
significant.

tags= tags /usr/ lib/ tags
Define pathname of files containing tags (see the
ctags command in Chapter 3, "Linux Commands").

By default, the system looks for files tags (in the
current directory) and /usr/ lib/ tags.

term= Set terminal type.
terse noterse Display shorter error messages.
timeout

(to)
timeout Keyboard maps timeout after 1second.

ttytype= Set terminal type. Default is inherited from TERM environment variable.
warn warn Display the message, "No write since last change."
window=

(w)
Show a certain number of lines of the file on the
screen. Default depends on line speed and terminal
type.

wrapmargin=

(wm)
0 Define right margin. If greater than 0, automatically insert carriage returns to break lines.

wrapscan
(ws)
ws Searches wrap around either end of file.

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vi Configuration (Linux in a Nutshell, 3rd Edition)
writeany
(wa)
nowa Allow saving to any file.

11.14.3. Sample ~/. exrc File
The following lines of code are an example of a customized .exrc file:
set nowrapscan wrapmargin= 7 set sections= SeAhBhChDh nomesg map q :w^ M: n^ M map v dwElp ab ORA O'Reilly & Associates, Inc.

11.13. Alphabetical
Summary of ex Commands
12. The sed Editor

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The sed Editor (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

Chapter 12. The sed Editor
Contents:
Conceptual Overview
Command-Line Syntax
Syntax of sed Commands
Group Summary of sed Commands
Alphabetical Summary of sed Commands

This chapter presents the following topics:
l Conceptual overview of sed

l Command-line syntax
l Syntax of sed commands
l Group summary of sed commands
l Alphabetical summary of sed commands

For more information, see the O'Reilly book sed & awk, 2d ed., by Dale Dougherty and
Arnold Robbins.

12.1. Conceptual Overview
sed is a noninteractive, or stream-oriented, editor. It interprets a script and performs the
actions in the script. sed is stream-oriented, because, as with many Unix programs, input
flows through the program and is directed to standard output. For example, sort is stream-oriented;
vi is not. sed's input typically comes from a file but can be directed from the
keyboard. Output goes to the screen by default but can be captured in a file instead.

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The sed Editor (Linux in a Nutshell, 3rd Edition)
Typical uses of sed include:

l Editing one or more files automatically

l Simplifying repetitive edits to multiple files
l Writing conversion programs

sed operates as follows:
l Each line of input is copied into a pattern space.

l All editing commands in a sed script are applied in order to each line of input.
l Editing commands are applied to all lines (globally) unless line addressing restricts the
lines affected.

l If a command changes the input, subsequent commands are applied to the changed
line, not to the original input line.

l The original input file is unchanged, because the editing commands modify a copy of
the original input line. The copy is sent to standard output (but can be redirected to a
file).

11.14. vi Configuration 12.2. Command-Line Syntax
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.

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Command-Line Syntax (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

12.2. Command-Line Syntax
The syntax for invoking sed has two forms:
sed [options] 'command' file( s)

sed [options] -f scriptfile file( s)The first form allows you to specify an editing command on the command line, surrounded by
single quotes. The second form allows you to specify a scriptfile, a file containing sed
commands. If no files are specified, sed reads from standard input.

The following options are recognized:
-e cmd
Next argument is an editing command; not needed unless specifying two or more
editing commands.

-f scriptfile
Next argument is a file containing editing commands.
-n
Suppress the default output; sed displays only those lines specified with the p
command or with the p flag of the s command.

-V
Display version number.
--quiet

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Command-Line Syntax (Linux in a Nutshell, 3rd Edition)
Same as -n.

--expression= cmd
Same as -e.
--file= file
Same as -f.
--help
Display brief help message with command-line options.
--silent
Same as -n.
--version
Same as -V.

12. The sed Editor 12.3. Syntax of sed
Commands

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Syntax of sed Commands (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

12.3. Syntax of sed Commands
sed commands have the general form:
[address[, address]][!] command [arguments]sed commands consist of addresses and editing commands. commands consist of a single letter or symbol; they are
described later, alphabetically and by group. arguments include the label supplied to b or t, the filename supplied to r or w,
and the substitution flags for s. addresses are described in the next section.

12.3.1. Pattern Addressing
A sed command can specify zero, one, or two addresses. An address can be a line number, the symbol $ (for last line), or a
regular expression enclosed in slashes (/ pattern/). Regular expressions are described in Chapter 9, "Pattern Matching".

Additionally, \n can be used to match any newline in the pattern space (resulting from the N command) but not the newline
at the end of the pattern space.

If the Command Specifies Then the Command Is Applied To
No address Each input line.

One address Any line matching the address. Some commands (a, i, r, q, and =) accept only one address.

Two comma-separated addresses First matching line and all succeeding lines up to and including a line matching the second address.
An address followed by ! All lines that do not match the address.

12.3.1.1. Examples
s/ xx/ yy/ g Substitute on all lines (all occurrences) /BSD/ d Delete lines containing BSD /^ BEGIN/,/^ END/ p Print between BEGIN and END, inclusive /SAVE/! d Delete any line that doesn't contain SAVE /BEGIN/,/ END/! s/ xx/ yy/ g Substitute on all lines, except between BEGIN and END

Braces ({}) are used in sed to nest one address inside another or to apply multiple commands at the same address:
[/ address/[,/ address/]]{ command1 command2}

The opening curly brace must end a line, and the closing curly brace must be on a line by itself. Be sure there are no blank
spaces after the braces.

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Syntax of sed Commands (Linux in a Nutshell, 3rd Edition)
12.2. Command-Line Syntax 12.4. Group Summary of sed
Commands

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Group Summary of sed Commands (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

12.4. Group Summary of sed Commands
In the following tables, the sed commands are grouped by function and are described tersely.
Full descriptions, including syntax and examples, can be found afterward in the alphabetical
summary.

12.4.1. Basic Editing

Command Action
a\ Append text after a line.
c\ Replace text (usually a text block).
i\ Insert text before a line.
d Delete lines.
s Make substitutions.
y Translate characters (like tr in Chapter 3, "Linux Commands").

12.4.2. Line Information
Command Action
= Display line number of a line.
l Display control characters in ASCII.
p Display the line.

12.4.3. Input/ Output Processing

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Group Summary of sed Commands (Linux in a Nutshell, 3rd Edition)
Command Action
n Skip current line and go to line below.
r Read another file's contents into the input.
w Write input lines to another file.
q Quit the sed script (no further output).

12.4.4. Yanking and Putting
Command Action
h Copy pattern space into hold space; wipe out what's there.
H Copy pattern space into hold space; append to what's there.
g Get the hold space back; wipe out the pattern space.
G Get the hold space back; append to pattern space.
x Exchange contents of hold space and pattern space.

12.4.5. Branching Commands
Command Action
b Branch to label or to end of script.
t Same as b, but branch only after substitution.
:label Label branched to by t or b.

12.4.6. Multiline Input Processing
Command Action
N Read another line of input (creates embedded newline).
D Delete up to the embedded newline.
P Print up to the embedded newline.

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Group Summary of sed Commands (Linux in a Nutshell, 3rd Edition)
12.3. Syntax of sed
Commands
12.5. Alphabetical Summary
of sed Commands

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Alphabetical Summary of sed Commands (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

12.5. Alphabetical Summary of sed Commands
# #
Begin a comment in a sed script. Valid only as the first character of the first line. (Some versions of
sed, including the GNU version on Linux, allow comments anywhere, but it is better not to rely on
this.) If the first line of the script is #n, sed behaves as if -n had been specified.

: :label
Label a line in the script for the transfer of control by b or t. label may contain up to seven
characters.

= [/ pattern/]=
Write to standard output the line number of each line containing pattern.

a [address] a\
text
Append text following each line matched by address. If text goes over more than one line, newlines
must be "hidden" by preceding them with a backslash. The text will be terminated by the first
newline that is not hidden in this way. The text is not available in the pattern space, and subsequent
commands cannot be applied to it. The results of this command are sent to standard output when the
list of editing commands is finished, regardless of what happens to the current line in the pattern
space.

Example
$a\ This goes after the last line in the file\ (marked by $). This text is escaped at the\ end of each line, except for the last one.

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b [address1[, address2]] b[ label]
Transfer control unconditionally to :label elsewhere in script. That is, the command following the
label is the next command applied to the current line. If no label is specified, control falls through to
the end of the script, so no more commands are applied to the current line.

Example
Ignore lines between .TS and .TE; resume script after .TE:
/^\. TS/,/^\. TE/ b

c [address1[, address2]] c\
text
Replace the lines selected by the address with text. When a range of lines is specified, all lines as a
group are replaced by a single copy of text. The newline following each line of text must be escaped
by a backslash, except the last line. The contents of the pattern space are, in effect, deleted, and no
subsequent editing commands can be applied.

Example
Replace first 100 lines in a file:
1,100c\ \ <First 100 names to be supplied>

d [address1[, address2]] d
Delete the addressed line (or lines) from the pattern space. Thus, the line is not passed to standard
output. A new line of input is read, and editing re sumes with the first command in the script.

Example
Delete all blank lines:
/^$/ d

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D [address1[, address2]] D
Delete first part (up to embedded newline) of multiline pattern space created by N command, and
resume editing with first command in script. If this command empties the pattern space, then a new
line of input is read, as if the d had been executed.

Example
Strip multiple blank lines, leaving only one:
/^$/{ N /^\ n$/ D}

g [address1[, address2]] g
Paste the contents of the hold space (see h or H command) back into the pattern space, wiping out
the previous contents of the pattern space. The example shows a simple way to copy lines.

Example
This script collects all lines containing the word Item: and copies them to a place marker later in the
file. The place marker is overwritten.

/Item:/ H /< Replace this line with the item list>/ g

G [address1[, address2]] G
Same as g, except that the hold space is pasted below the address instead of overwriting it. The
example shows a simple way to cut and paste lines.

Example
This script collects all lines containing the word Item: and moves them after a place marker later in
the file. The original Item: lines are deleted.

/Item:/{ H d } /Summary of items:/ G

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h [address1[, address2]] h
Copy the pattern space into the hold space, a special temporary buffer. The previous contents of the
hold space are obliterated. You can use h to save a line before editing it.

Example
# Edit a line; print the change; replay the original /Linux/{ h s/.* Linux $.*$ .*/\ 1:/ p x }

Sample input:
This describes the Linux ls command. This describes the Linux cp command.

Sample output:
ls: This describes the Linux ls command. cp: This describes the Linux cp command.

H [address1[, address2]] H
Append the contents of the pattern space (preceded by a newline) to the contents of the hold space.
Even if the hold space is empty, H still appends a newline. H is like an incremental copy. See
examples under g and G.

i [address1] i\
text
Insert text before each line matched by address. (See a for details on text.)
Example
/Item 1/ i\ The five items are listed below:

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l [address1[, address2]] l
List the contents of the pattern space, showing nonprinting characters as ASCII codes. Long lines are
wrapped.

n [address1[, address2]] n
Read next line of input into pattern space. The current line is sent to standard output, and the next
line becomes the current line. Control passes to the command following n instead of resuming at the
top of the script.

Example
In the ms macros, a section header occurs on the line below an .NH macro. To print all lines of
header text, invoke this script with sed -n:

/^\. NH/{ n p }

N [address1[, address2]] N
Append next input line to contents of pattern space; the two lines are separated by an embedded
newline. (This command is designed to allow pattern matches across two lines.) Using \n to match
the embedded newline, you can match patterns across multiple lines. See example at D.

Examples
Like previous example, but print .NH line as well as header title:
/^\. NH/{ N p }

Join two lines (replace newline with space):
/^\. NH/{ N s/\ n/ / p }

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p [address1[, address2]] p
Print the addressed lines. Unless the -n command-line option is used, this command causes duplicate
lines to be output. Also, it typically is used before commands that change flow control (d, N, b) and
that might prevent the current line from being output. See examples at h, n, and N.

P [address1[, address2]] P
Print first part (up to embedded newline) of multiline pattern created by N command. Same as p if N
has not been applied to a line.

q [address] q
Quit when address is encountered. The addressed line first is written to output (if default output is
not suppressed), along with any text appended to it by previous a or r commands.

Examples
Delete everything after the addressed line:
/Garbled text follows:/ qPrint only the first 50 lines of a file:
50q

r [address] r file
Read contents of file and append after the contents of the pattern space. Exactly one space must be
put between the r and the filename.

Example
/The list of items follows:/ r item_ file

s [address1[, address2]] s/ pattern/ replacement/[ flags]
Substitute replacement for pattern on each addressed line. If pattern addresses are used, the pattern //
represents the last pattern address specified. The following flags can be specified:

n
Replace nth instance of /pattern/ on each addressed line. n is any number in the range 1 to
512; the default is 1.

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Replace all instances of /pattern/ on each addressed line, not just the first instance.
p
Print the line if a successful substitution is done. If several successful substitutions are done,
multiple copies of the line will be printed.

w file
Write the line to a file if a replacement was done.
Examples
Here are some short, commented scripts:
# Change third and fourth quote to ( and ): /function/{ s/"/(/ 3 s/"/)/ 4 }

# Remove all quotes on a given line: /Title/ s/"// g

# Remove first colon or all quotes; print resulting lines: s/:// p s/"// gp

# Change first "if" but leave "ifdef" alone: /ifdef/! s/ if/ if/

t [address1[, address2]] t [label]
Test if any substitutions have been made on addressed lines, and if so, branch to line marked by
:label. (See b and :.) If label is not specified, control falls through to bottom of script. The t
command is like a case statement in the C programming language or the shell programming
languages. You test each case; when it's true, you exit the construct.

Example
Suppose you want to fill empty fields of a database. You have this:
ID: 1 Name: greg Rate: 45 ID: 2 Name: dale ID: 3

You want this:
ID: 1 Name: greg Rate: 45 Phone: ?? ID: 2 Name: dale Rate: ?? Phone: ??

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ID: 3 Name: ???? Rate: ?? Phone: ??

You need to test the number of fields already there. Here's the script (fields are tab-separated):
/ID/{ s/ ID: .* Name: .* Rate: .*/& Phone: ??/ p t s/ ID: .* Name: .*/& Rate: ?? Phone: ??/ p t s/ ID: .*/& Name: ?? Rate: ?? Phone: ??/ p }

w [address1[, address2]] w file
Append contents of pattern space to file. This action occurs when the command is encountered,
rather than when the pattern space is output. Exactly one space must separate the w and the filename.
This command will create the file if it does not exist; if the file exists, its contents will be overwritten
each time the script is executed. Multiple write commands that direct output to the same file append
to the end of the file.

Example
# Store tbl and eqn blocks in a file: /^\. TS/,/^\. TE/ w troff_ stuff /^\. EQ/,/^\. EN/ w troff_ stuff

x [address1[, address2]] x
Exchange contents of the pattern space with the contents of the hold space. See h for an example.

y [address1[, address2]] y/ abc/ xyz/
Translate characters. Change every instance of a to x, b to y, c to z, etc.
Example
# Change item 1, 2, 3 to Item A, B, C ... /^ item [1-9]/ y/ 123456789/ ABCDEFGHI/

12.4. Group Summary of sed
Commands
13. The gawk Scripting
Language

Copyright © 2001 O'Reilly & QKFIN. All rights reserved.
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Edition

Chapter 13. The gawk Scripting
Language
Contents:
Conceptual Overview
Command-Line Syntax
Patterns and Procedures
gawk System Variables
Operators
Variable and Array Assignments
Group Listing of gawk Commands
Alphabetical Summary of Commands

gawk is the GNU version of awk, a powerful pattern-matching program for processing text
files that may be composed of fixed or variable length records separated by some delineator
(by default, a newline character). gawk may be used from the command line or in gawk
scripts. Normally you should be able to invoke this utility using either awk or gawk on the
shell command line.

This chapter presents the following topics:
l Conceptual overview

l Command-line syntax
l Patterns and procedures
l System variables
l Operators

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l Variable and array assignment

l Group listing of commands
l Alphabetical summary of commands

For more information, see the O'Reilly book sed & awk, 2d ed., by Dale Dougherty and
Arnold Robbins.

13.1. Conceptual Overview
With gawk, you can:
l Conveniently process a text file as though it were made up of records and fields in a
textual database.

l Use variables to change the database.

l Execute shell commands from a script.
l Perform arithmetic and string operations.
l Use programming constructs such as loops and conditionals.
l Define your own functions.
l Process the result of shell commands.
l Process command-line arguments more gracefully.
l Produce formatted reports.

12.5. Alphabetical Summary
of sed Commands
13.2. Command-Line Syntax

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13.2. Command-Line Syntax
gawk's syntax has two forms:
gawk [options] 'script' var= value file( s)gawk [options] -f scriptfile var= value file( s)

You can specify a script directly on the command line, or you can store a script in a scriptfile
and specify it with -f. Multiple -f options are allowed; awk concatenates the files. This feature
is useful for including libraries.

gawk operates on one or more input files. If none are specified (or if -is specified), gawk
reads from the standard input.

Variables can be assigned a value on the command line. The value assigned to a variable can
be a literal, a shell variable ($ name), or a command substitution (`cmd`), but the value is
available only after a line of input is read (i. e., after the BEGIN statement).

For example, to print the first three (colon-separated) fields of the password file, use -F to set
the field separator to a colon:

gawk -F: '{ print $1; print $2; print $3} ' /etc/ passwdNumerous examples are shown later in Section 13.3, "Patterns and Procedures".

13.2.1. Options
All options exist in both traditional POSIX (one-letter) format and GNU-style (long) format.
Some recognized options are:

--
Treat all subsequent text as commands or filenames, not options.

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-f scriptfile, --file= scriptfile

Read gawk commands from scriptfile instead of command line.
-v var= value, --assign= var= value
Assign a value to variable var. This allows assignment before the script begins
execution.

-Fc, --field-separator= c
Set the field separator to character c. This is the same as setting the variable FS. c may
be a regular expression. Each input line, or record, is divided into fields by whitespace
(blanks or tabs) or by some other user-definable record separator. Fields are referred to
by the variables $1, $2,..., $n. $0 refers to the entire record.

-W option
All -W options are specific to gawk, as opposed to awk. An alternate syntax is --
option (i. e., --compat). option may be one of:

compat
Same as traditional.
copyleft
Print copyleft notice and exit.
copyright
Same as copyleft.
help
Print syntax and list of options, then exit.
lint
Warn about commands that might not port to other versions of awk or that
gawk considers problematic.

lint-old

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Like lint but compares to an older version of awk.

posix
Expect exact compatibility with POSIX; additionally, ignore \x escape
sequences, **, and **=.

re-interval
Allow use of {n, m} intervals in regular expressions.
source= script
Treat script as gawk commands. Like the 'script' argument but lets you mix
commands from files (using -f options) with commands on the gawk command
line.

traditional
Behave exactly like traditional (non-GNU) awk.
usage
Same as help.
version
Print version information and exit.

13. The gawk Scripting
Language
13.3. Patterns and Procedures

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13.3. Patterns and Procedures
gawk scripts consist of patterns and procedures:
pattern {procedure}Both are optional. If pattern is missing, {procedure} is applied to all records. If {procedure} is
missing, the matched record is printed. By default, each line of input is a record, but you can
specify a different record separator through the RS variable.

13.3.1. Patterns
A pattern can be any of the following:
/regular expression/ relational expression pattern-matching expression pattern, patternBEGIN END

Some rules regarding patterns include:
l Expressions can be composed of quoted strings, numbers, operators, functions, defined
variables, or any of the predefined variables described later under "gawk System
Variables."

l Regular expressions use the extended set of metacharacters and are described in
Chapter 9, "Pattern Matching".
l In addition, ^ and $ can be used to refer to the beginning and end of a field,

respectively, rather than the beginning and end of a record. l
Relational expressions use the relational operators listed under "Operators" later in this
chapter. Comparisons can be either string or numeric. For example, $2 > $1 selects
lines for which the second field is greater than the first. l
Pattern-matching expressions use the operators ~ (match) and !~ (don't match). See

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Patterns and Procedures (Linux in a Nutshell, 3rd Edition)
"Operators" later in this chapter. l
The BEGIN pattern lets you specify procedures that take place before the first input
record is processed. (Generally, you set global variables here.) l
The END pattern lets you specify procedures that take place after the last input record
is read. l
If there are multiple BEGIN or END patterns, their associated actions are taken in the
order in which they appear in the script. l
pattern, pattern specifies a range of lines. This syntax cannot include BEGIN or END
as a pattern.

Except for BEGIN and END, patterns can be combined with the Boolean operators || (OR),
&& (AND), and ! (NOT).

In addition to other regular-expression operators, GNU awk supports POSIX character lists,
which are useful for matching non-ASCII characters in languages other than English. These
lists are recognized only within [ ] ranges. A typical use would be [[: lower:]], which in
English is the same as [a-z]. See Chapter 9, "Pattern Matching" for a complete list of POSIX

character lists.

13.3.2. Procedures
Procedures consist of one or more commands, functions, or variable assignments, separated
by newlines or semicolons and contained within curly braces. Commands fall into four
groups:

l Variable or array assignments

l Printing commands
l Built-in functions
l Control-flow commands

13.3.3. Simple Pattern-Procedure Examples
1. Print first field of each line (no pattern specified):
{ print $1 }2. Print all lines that contain "Linux":
/Linux/3. Print first field of lines that contain "Linux":
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/Linux/{ print $1 }4. Print records containing more than two fields:
NF > 25. Interpret each group of lines up to a blank line as a single input record:
BEGIN { FS = "\ n"; RS = "" }6. Print fields 2 and 3 in switched order but only on lines whose first field matches the
string "URGENT":

$1 ~ /URGENT/ { print $3, $2 }7. Count and print the number of instances of "ERR" found:
/ERR/ { ++ x }; END { print x }8. Add numbers in second column and print total:
{total += $2 }; END { print "column total is", total}9. Print lines that contain fewer than 20 characters:
length() < 2010. Print each line that begins with "Name:" and that contains exactly seven fields:
NF == 7 && /^ Name:/11. Reverse the order of fields:
{ for (i = NF; i >= 1; i--) print $i }

13.2. Command-Line Syntax 13.4. gawk System Variables
Copyright © 2001 O'Reilly & QKFIN. All rights reserved.
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13.4. gawk System Variables
Variable Description
$n nth field in current record; fields are separated by FS
$0 Entire input record
ARGC Number of arguments on command line
ARGIND Current file's place in command line (starting with 0)
ARGV An array containing the command-line arguments
CONVFMT Conversion format for numbers (default is %. 6g)
ENVIRON An associative array of environment variables
ERRNO Description of last system error
FIELDWIDTHS List of field widths (whitespace-separated)
FILENAME Current filename
FNR Like NR, but relative to the current file

FS Field separator (default is any whitespace; null string separates into individual characters)
IGNORECASE If true, make case-insensitive matches
NF Number of fields in current record
NR Number of the current record
OFMT Output format for numbers (default is %. 6g)
OFS Output field separator (default is a blank)
ORS Output record separator (default is a newline)

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RLENGTH Length of the string matched by match function
RS Record separator (default is a newline)
RSTART First position in the string matched by match function
SUBSEP Separator character for array subscripts (default is \034)

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Operators (Linux in a Nutshell, 3rd Edition)
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13.5. Operators
The following table lists the operators, in order of increasing precedence, that are available in
gawk.

Symbol Meaning
= += -= *= /= %= ^= **= Assignment
?: C conditional expression
|| Logical OR
&& Logical AND
~ !~ Match regular expression and negation
< <= > >= != == Relational operators
(blank) Concatenation
+ -Addition, subtraction
* / % Multiplication, division, and modulus
+ -! Unary plus and minus and logical negation
^ ** Exponentiation
++ --Increment and decrement, either prefix or postfix
$ Field reference
in Array membership (see for command)

13.4. gawk System Variables 13.6. Variable and Array
Assignments

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13.6. Variable and Array Assignments
Variables can be assigned a value with an equals sign. For example:
FS = ","Expressions using the operators +, -, /, and % (modulo) can be assigned to variables.
Arrays can be created with the split function (see the listing in Section 13.8, "Alphabetical
Summary of Commands"), or they can simply be named in an assignment statement. Array
elements can be subscripted with numbers (array[ 1]) or with names. For example, to count
the number of occurrences of a pattern, you could use the following script:

/pattern/ { array["/ pattern/"]++ } END { printarray["/ pattern/"] }

In gawk, variables need not be declared previous to their use, nor do arrays need to be
dimensioned; they are activated upon first reference. All variables are stored as strings but
may be used either as strings or numbers. gawk will use the program script context to
determine whether to treat a variable as a string or a number, but the distinction also can be
forced by the user. To force a variable to be treated as a string, catenate a null to the variable:

var ""To force a variable to be treated as a number, add 0 to it:
var + 0

13.5. Operators 13.7. Group Listing of gawk
Commands

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13.7. Group Listing of gawk Commands
gawk commands may be classified as follows:

Arithmetic
Functions
String
Functions
Control Flow
Statements
Input/ Output
Processing
Time
Functions Misc.

atan2 gensub break close strftime delete
cos gsub continue fflush systime function
exp index do/ while getline system
int length exit next
log match for nextfile
rand split if print
sin sub return printf
sqrt substr sprintf
srand tolower while
toupper

13.6. Variable and Array
Assignments
13.8. Alphabetical Summary
of Commands

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13.8. Alphabetical Summary of Commands
The following alphabetical list of statements and functions includes all that are available in gawk in Linux.

atan2 atan2( y, x)
Return the arctangent of y/ x in radians.

break break
Exit from a while or for loop.

close close( filename-expr)
close( command-expr)
Close a file read by a getline command or a pipe; takes as an argument the same expression that opened
the pipe or file.

continue continue
Begin next iteration of while or for loop without reaching the bottom.

cos cos( x)
Return the cosine of x, an angle in radians.

delete delete array[ element]
delete array
Delete element of array. If no element is specified, all elements are deleted.

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do do
body
while( expr)
Looping statement. Execute statements in body, then evaluate expr. If expr is true, execute body again.

exit exit
Do not execute remaining instruction, and read no new input. END procedures will be executed.

exp exp( arg)
Return the natural exponent of arg (the inverse of log).

fflush fflush( filename)
Flushes output to filename; default is the standard output.

for for( i= lower ; i<= upper ; i++)
command
While the value of variable i is in the range between lower and upper, do command. A series of
commands must be put within braces. <= or any relational operator can be used; ++ or --can be used to
increment or decrement the variable.

for for( item in array)
command
For each item in an associative array, do command. Multiple commands must be put inside braces.
Refer to each element of the array as array[ item]. Elements of gawk arrays are stored in an order that
enables access of any element in essentially equivalent time. This order may appear to be
indiscriminate; if the output is desired in sorted order, you must pipe it through the sort command.

function function name( parameter-list) {
statements
}
Create name as a user-defined function consisting of gawk statements that apply to the specified list of
parameters.

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gensub gensub( r, s, n, t)
Substitute s for the nth match of regular expression r in the string t. Leave t unchanged, but return new
string as the result. If n is "g" or "G" change all matches. If t is not supplied, it defaults to $0.

getline getline [varhairsp;] [< file]
command | getline [var]
The first form reads input from file or the next file on the command line, and the second form reads the
output of command. Both forms read one line at a time, and each time the statement is executed it gets
the next line of input. The line of input is assigned to $0 and is parsed into fields, setting NF, NR, and
FNR. If var is specified, the result is assigned to var, and neither $0 nor NF is changed. Thus, if the
result is assigned to a variable, the current line does not change. getline is actually a function, and it
returns 1 if it reads a record successfully, 0 at EOF, and -1 if for some reason it is otherwise
unsuccessful.

gsub gsub( r, s, t)
Globally substitute s for each match of the regular expression r in the string t. Return the number of
substitutions. If t is not supplied, it defaults to $0.

if if (condition)
command1
[else
command2]
If condition is true, do command1; otherwise, do command2. Condition can be an expression using any
of the relational operators <, <=, ==, !=, >=, or >, as well as the pattern-matching operator ~. A series of
commands must be put within braces.

Example
The following lines determine whether the first word in each line starts with A, uppercase or lowercase:
if ($ 1 ~ /[ Aa]*/) ... Begins with A or a

index index( substr, str)
Return the position of a substring in a string. Returns 0 if substr is not contained in str.

int int( arg)
Return the integer part of arg.

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length length( arg)
Return the length of arg. If arg is not supplied, $0 is assumed.

log log( arg)
Return the natural logarithm of arg (the inverse of exp).

match match( s, r)
Return position in s where regular expression r first matches or 0 if no occurrences are found. Sets the
value of RSTART and RLENGTH.

next next
Read next input line and start new cycle through pattern/ procedures statements.

nextfile nextfile
Skip to the next file on the gawk command line and start new cycle through pattern/ procedures
statements.

print print [args] [destination]
Print args on output. Literal strings must be quoted. Fields are printed in the order they are listed. If
separated by commas in the argument list, they are separated in the output by the character specified by
OFS. If separated by spaces, they are concatenated in the output. destination is a shell redirection or
pipe expression (e. g., > file) that redirects the default output.

printf printf [format [, expressions]]
Formatted print statement. Expressions or variables can be formatted according to instructions in the
format argument. The number of expressions must correspond to the number specified in the format
sections.

format follows the conventions of the C-language printf statement. Here are a few of the most common
formats:

%s
A string.
%d
A decimal number.
%n. mf
A floating point number. n = total number of digits; m = number of digits after decimal point.

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%[-] nc
n specifies minimum field length for format type c, while -left-justifies value in field; otherwise,
value is right-justified.

Field widths are adjustable. For example, %3.2f limits a floating-point number to a total width of three
digits, with two digits after the decimal point.

format also can contain embedded escape sequences, \n (newline) and \t (tab) being the most common.
Spaces and literal text can be placed in the format argument by quoting the entire argument. If there are
multiple expressions to be printed, multiple formats should be specified.

Example
Using the script:
{printf (" The sum on line %s is %d.\ n", NR, $1+$ 2)}the following input line:
5 5produces this output, followed by a newline:
The sum on line 1 is 10.

rand rand( )
Generate a random number between 0 and 1. This function returns the same series of numbers each
time the script is executed, unless the random number generator is seeded using the srand function.

return return [expr]
Used at end of user-defined functions to exit function, returning the value of expr.

sin sin( x)
Return the sine of x, an angle in radians.

split split( string, array[, sep])
Split string into elements of array array[ 1],..., array[ n]. The string is split at each occurrence of
separator sep. If sep is not specified, FS is used. If sep is a null string, a split is performed on every
character. The number of array elements created is returned.

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sprintf sprintf [format [, expression( s)]]
Return the value of one or more expressions, using the specified format (see printf). Data is formatted
but not printed.

sqrt sqrt( arg)
Return square root of arg.

srand srand( expr)
Use expr to set a new seed for random number generator. Default is time of day.

strftime strftime([ format [, timestamp]])
Format timestamp according to format. Return the formatted string. The timestamp is a time-of-day
value in seconds since midnight, January 1, 1970, UTC. The format string is similar to that of sprintf.
(See the example for systime.) If timestamp is omitted, it defaults to the current time. If format is
omitted, it defaults to a value that produces output similar to that of date.

sub sub( r, s, t)
Substitute s for first match of the regular expression r in the string t. Return 1 if successful; 0 otherwise.
If t is not supplied, the default is $0.

substr substr( string, m[, n])
Return substring of string beginning at character position m and consisting of the next n characters. If n
is omitted, include all characters to the end of string.

system system( command)
Execute the specified shell command and return its status. The status of the command that is executed
typically indicates its success (1), completion (0), or unexpected error (-1). The output of the command
is not available for processing within the gawk script.

systime systime()
Return number of seconds since midnight UTC, January 1, 1970.
Example
Log the start and end times of a data-processing program:
BEGIN { now = systime() mesg = strftime(" Started at %m/% d/% Y %H:% M:% S", now) print mesg

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}process data ...END { now = systime() mesg = strftime(" Ended at %m/% d/% Y %H:% M:% S", now) print mesg }

tolower tolower( str)
Translate all uppercase characters in str to lowercase and return the new string.

toupper toupper( str)
Translate all lowercase characters in str to uppercase and return the new string.

while while (condition)
command
Do command while condition is true (see if for a description of allowable conditions). A series of
commands must be put within braces.

13.7. Group Listing of gawk
Commands
14. CVS and RCS

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Chapter 14. CVS and RCS
Contents:
Basic Concepts
The CVS Utility
CVS Administrator Reference
CVS User Reference
The RCS Utility
Overview of RCS Commands
Basic RCS Operations
General RCS Specifications
Alphabetical Summary of RCS Commands

CVS, and the older RCS, offer version control (or revision control), the practice of
maintaining information about a project's evolution so that prior versions may be retrieved,
changes tracked, and, most importantly, the efforts of a team of developers coordinated.

14.1. Basic Concepts
RCS (Revision Control System) works within a single directory. To accommodate large
projects using a hierarchy of several directories, CVS creates two new concepts called the
repository and the sandbox.

The repository (also called an archive) is the centralized storage area, managed by the version
control system and the repository administrator, which stores the projects' files. The repository
contains information required to reconstruct historical versions of the files in a project. An
administrator sets up and controls the repository using the procedures and commands later in
Section 14.3, "CVS Administrator Reference".

A sandbox (also called a working directory) contains copies of versions of files from the
repository. New development occurs in sandboxes, and any number of sandboxes may be
created from a single repository. The sandboxes are independent of one another and may

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contain files from different stages of the development of the same project. Users set up and
control sandboxes using the procedures and commands found in Section 14.4, "CVS User

Reference", later in this chapter.

In a typical interaction with the version control system, a developer checks out the most
current code from the repository, makes changes, tests the results, and then commits those
changes back to the repository when they are deemed satisfactory.

14.1.1. Locking and Merging
Some systems, including RCS, use a locking model to coordinate the efforts of multiple
developers by serializing file modifications. Before making changes to a file, a developer
must not only obtain a copy of it, but he must also request and obtain a lock on it from the
system. This lock serves to prevent (really dissuade) multiple developers from working on the
same file at the same time. When the changes are committed, the developer unlocks the file,
permitting other developers to gain access to it.

The locking model is pessimistic: it assumes that conflicts must be avoided. Serialization of
file modifications through locks prevents conflicts. But it is cumbersome to have to lock files
for editing when bug-hunting. Often, developers will circumvent the lock mechanism to keep
working, which is an invitation to trouble.

Unlike RCS and SCCS, CVS uses a merging model which allows everyone to have access to
the files at all times and supports concurrent development. The merging model is optimistic: it
assumes that conflicts are not common and that when they do occur, it usually isn't difficult to
resolve them.

CVS is capable of operating under a locking model via the -L and -l options to the admin
command. Also, CVS has special commands (edit and watch) for those who want additional
development coordination support. CVS uses locks internally to prevent corruption when
multiple people are accessing the repository simultaneously, but this is different from the user-visible
locks of the locking model discussed here.

14.1.2. Conflicts and Merging
In the event that two developers commit changes to the same version of a file, CVS
automatically defers the commit of the second committer's file. The second developer then
issues the cvs update command, which merges the first developer's changes into the local file.
In many cases, the changes will be in different areas of the file, and the merge is successful.
However, if both developers have made changes to the same area of the file, the second to
commit will have to resolve the conflict. This involves examination of the problematic area( s)
of the file and selection among the multiple versions or making changes that resolve the
conflict.

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CVS only detects textual conflicts, but conflict resolution is concerned with keeping the
project as a whole logically consistent. Therefore, conflict resolution sometimes involves
changing files other than the one about which CVS complained.

For example, if one developer adds a parameter to a function definition, it may be necessary
for all the calls to that function to be modified to pass the additional parameter. This is a
logical conflict, so its detection and resolution is the job of the developers (with support from
tools like compilers and debuggers); CVS won't notice the problem.

In any merge situation, whether or not there was a conflict, the second developer to commit
will often want to retest the resulting version of the project because it has changed since the
original commit. Once it passes, the developer will need to recommit the file.

14.1.3. Tagging
CVS tracks file versions by revision number, which can be used to retrieve a particular
revision from the repository. In addition, it is possible to create symbolic tags so that a group
of files (or an entire project) can be referred to by a single identifier even when the revision
numbers of the files are not the same (which is most often the case). This capability is often
used to keep track of released versions or other important project milestones.

For example, the symbolic tag hello-1_ 0 might refer to revision number 1.3 of hello. c and
revision number 1.1 of Makefile (symbolic tags are created with the tag and rtag commands).

14.1.4. Branching
The simplest form of development is linear, in which there is a succession of revisions to a
file, each derived from the prior revision. Many projects can get by with a completely linear
development process, but larger projects (as measured by number of files, number of
developers, and/ or the size of the user community) often run into maintenance issues that
require additional capabilities. Sometimes, it is desirable to do some speculative development
while the main line of development continues uninterrupted. Other times, bugs in the currently
released version must be fixed while work on the next version is underway. In both of these
cases, the solution is to create a branch (fork) from an appropriate point in the development of
the project. If at a future point some or all of the changes on the branch are needed back on the
main line of development (or elsewhere), they can be merged in (joined).

Branches are forked with the tag -b command; they are joined with the update -j command.

13.8. Alphabetical Summary
of Commands
14.2. The CVS Utility

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14.2. The CVS Utility
This section offers general background about CVS.

14.2.1. CVS Command Format
CVS commands are of the form:
cvs global_ options command command_ optionsFor example, here is a simple sequence of commands showing both kinds of options in the context of creating a repository,
importing existing files, and performing a few common operations on them:

user@ localhost$ cvs -d /usr/ local/ cvsrep inituser@ localhost$ cd ~/ work/ hellouser@ localhost$ cvs -d /usr/ local/ cvsrep import -m 'Import' hello vendor startuser@ localhost$ cd ..user@ localhost$ mv hello hello. bakuser@ localhost$ cvs -d /usr/ local/ cvsrep checkout hellouser@ localhost$ cd hellouser@ localhost$ vi hellouser@ localhost$ cvs commit -m 'Fixed a typo'user@ localhost$ cvs tag hello-1_ 0user@ localhost$ cvs remove -f Makefileuser@ localhost$ cvs commit -m 'Removed old Makefile'user@ localhost$ cvs upd -r hello-1_ 0user@ localhost$ cvs upd -A

Some global options are common to both user and administrator commands, and some are specific to each of these. The
common global options are described in the next section, and the user and administrator options are described in the
Section 14.4, "CVS User Reference" and Section 14.3, "CVS Administrator Reference" sections, respectively.

14.2.2. Common Global Options
Table 14-1 lists the global options that apply to both user and administrator commands.

Table 14-1. Common Global Options

Option Description
-b bindir Location of external RCS programs. This option is obsolete, having been deprecated at CVS versions above 1.9.18.
-T tempdir Absolute path for temporary files. Overrides the setting of $TMPDIR.

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-v
--version
Display version and copyright information.

14.2.3. Gotchas
This section clarifies a few aspects of CVS that can sometimes cause confusion.
CVS's file orientation
While directories are supported, they are not versioned in the same way as traditional files. This is particularly
important in the early evolutionary stages of a project, when the structure may be in flux. Also, if the project is
undergoing major changes, the structure is likely to change. See later in Section 14.3.4, "Hacking the Repository".

CVS's text-orientation

There is no equivalent to diff for binary files, although CVS's support for binary files is usually sufficient. Use
admin -kb to tell CVS a file is binary.
CVS's line-orientation

Moving a segment of code from one place in a file to another is seen as one delete (from the old location) and an
unrelated add (to the new location).
CVS is not syntax-aware

As far as CVS is concerned, small formatting changes are equivalent to sweeping logic changes in the same line
ranges.
RCS anachronisms

CVS was originally built on top of RCS, but now all the RCS-related functionality is internal to CVS itself. RCS
still shows up in the name of the $RCSBIN environment variable and the description of the -b option, which are
now obsolete.

14. CVS and RCS 14.3. CVS Administrator
Reference

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14.3. CVS Administrator Reference
This section provides details on creating and configuring repositories and performing other CVS
administrative tasks. A single computer can run multiple copies of the CVS server, and each server can serve
multiple repositories.

14.3.1. Creating a Repository
Select a directory that will contain the repository files (/ usr/ local/ cvsrep is used in the following examples).
Use the init command to initialize the repository. Either set the $CVSROOT environment variable first:

user@ localhost$ export CVSROOT=/ usr/ local/ cvsrepuser@ localhost$ cvs init

or use the -d option to specify the repository location:
user@ localhost$ cvs -d /usr/ local/ cvsrep initFor information on importing code, see Section 14.4, "CVS User Reference", especially Section 14.4.7.11,
"import" and Section 14.4.7.1, "add" sections.

14.3.1.1. Setting up the password server
If you want users to access the repository from other computers, then configure the pserver by doing the
following as root:

l Make sure there is an entry in /etc/ services similar to the following:

cvspserver 2401/ tcpl If you are not using tcpwrappers, then place a line like this in /etc/ inetd. conf:

cvspserver stream tcp nowait root /usr/ bin/ cvs cvs --allow-root=/ usr/ local/ cvsroot pserver

l Or, if you are using tcpwrappers, then use a line like this:

cvspserver stream tcp nowait root /usr/ sbin/ tcpd /usr/ bin/ cvs --allow-root=/ usr/ local/ cvsroot pserver

l Once these changes are in place, restart inetd (or send it the appropriate signal to cause it to re-read
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inetd. conf).

14.3.2. Security Issues
The following are security issues that need to be considered when working with CVS:
l The contents of files will be transmitted in the open over the network with pserver and rsh. With
pserver, passwords are transmitted in the open as well.

l When using a local repository (i. e., when CVS is not being used in client/ server mode), developers
need write access to the repository, which means they can hack it.

l The CVS server runs as root briefly before changing its user ID.

l The ~/. cvspass file must be kept unreadable by all users except the owner to prevent passwords from
being accessible.

l A user who has authority to make changes to the files in the CVSROOT module can run arbitrary
programs.

l Some of the options to the admin command are very dangerous, so it is advisable to restrict its use.
This can be accomplished by creating a user group named cvsadmin. If this user group exists, then
only users in that group can run the admin command (except admin -kkflag, which is available to
everyone).

14.3.3. Repository Structure
The CVS repository is implemented as a normal directory with special contents. This section describes the
contents of the repository directory.

14.3.3.1. The CVSROOT directory
The CVSROOT directory contains the administrative files for the repository; other directories in the repository
contain the modules. The administrative files permit (and ignore) blank lines and comment lines in addition to
the lines with real configuration information on them. Comment lines start with a hash mark (`# ').

Some of the administrative files contain filename patterns to match file and directory names. These patterns
are regular expressions like those used in GNU Emacs. Table 14-2 contains the special constructions used

most often.

Table 14-2. Filename Pattern Special Constructions

Construction Description

^ Match the beginning of the string.
$ Match the end of the string.
. Match any single character.

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* Modify the preceding construct to match zero or more repetitions.

CVS will perform a few important expansions in the contents of the administrative files before interpreting
the results. First, the typical shell syntax for referring to a home directory is ~/, which expands to the home
directory of the user running CVS; and ~user expands to the home directory of the specified user.

In addition, CVS provides a mechanism similar to the shell's environment variable expansion capability.
Constructs such as ${ variable} will be replaced by the value of the named variable. Variable names start
with letters and consist entirely of letters, numbers, and underscores. Curly brackets may be omitted if the
character immediately following the variable reference is not a valid variable name character. While this
construct looks like a shell environment variable reference, the full environment is not available. Table 14-3

contains the built-in variables.

Table 14-3. Administrative File Variables

Variable Description

CVSEDITOR
EDITOR
VISUAL
The editor CVS uses for log file editing.

CVSROOT The repository locator in use.
USER The name of the user (on the server, if using a remote repository) running CVS.

=var The value of a user-defined variable named var. Values for these variables are provided by the global -s option.

In order to edit these files, check out the CVSROOT module from the repository, edit the files, and commit
them back to the repository. You must commit the changes for them to affect CVS's behavior.

Table 14-4 describes the administrative files and their functions.

Table 14-4. CVSROOT Files

File Description

checkoutlist Extra files to be maintained in CVSROOT
commitinfo Specifications for commit governors
config Settings to affect the behavior of CVS
cvsignore Filename patterns of files to ignore
cvswrappers Specifications for checkout and commit filters
editinfo Specifications for log editors (obsolete)

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history Log information for the history command
loginfo Specify commit notifier program( s)
modules Module definitions
notify Notification processing specifications
passwd A list of users and their CVS-specific passwords
rcsinfo Template form for log messages
readers A list of users having read-only access
taginfo Tag processing specifications
users Alternate user email addresses for use with notify
verifymsg Specify log message evaluator program
writers A list of users having read/ write access

Since the editinfo file is obsolete, use the $EDITOR environment variable (or the -e option) to specify the
editor and the verifymsg file to specify an evaluator.

Each line of the taginfo file contains a filename pattern and a command line to execute when files with
matching names are tagged.

14.3.3.2. The checkoutlist file
Whenever changes to files in the CVSROOT module are committed, CVS prints the message:
cvs commit: Rebuilding administrative file databaseto inform you that the checked-out copy in the repository has been updated to reflect any changes just
committed. As with any other module directory in the repository, the CVSROOT directory contains RCS (*, v)
files that retain the history of the files. But to use the files, CVS needs a copy of the latest revision. So, when
CVS prints this message, it is checking out the latest revisions of the administrative files.

If you have added files to the CVSROOT module (such as scripts to be called via entries in the loginfo file),
you will need to list them in the checkoutlist file. This makes CVS treat them the same way as it treats the
standard set of CVSROOT files.

Each line in this file consists of a filename and an optional error message that is displayed in case there is
trouble checking out the file.

14.3.3.3. The commitinfo file
Whenever a commit is being processed, CVS consults this file to determine whether or not any precommit
checking of the file is required. Each line of the file contains a directory name pattern, followed by the path of
a program to invoke when files are commited in directories with matching names.

Aside from the usual filename-pattern syntax, there are two special patterns:

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ALLIf this pattern is present in the file, then all files are passed to the specified checking program. CVS
then looks for a pattern that matches the name of each particular file and runs the additional checks
found, if any.

DEFAULTIf this pattern is present in the file, all files for which there was no pattern match are sent to the
specified checking program. The automatic match of every file to the ALL entry, if any, does not count
as a match when determining whether or not to send the file to the DEFAULT checking program.

CVS constructs the command line for the checking program by appending the full path to the directory within
the repository and the list of files being committed (this means you can specify the first few command-line
arguments to the program, if necessary). If the checking program exits with a nonzero status, the commit is
aborted.

The programs that run via this mechanism run on the server computer when a remote repository is used. Here
is an example of a commitinfo file:

ALL $CVSROOT/ CVSROOT/ commit-ALL. pl DEFAULT $CVSROOT/ CVSROOT/ commit-DEFAULT. pl CVSROOT$ $CVSROOT/ CVSROOT/ commit-CVSROOT. pl

This example assumes you will create the script files in the CVSROOT module and add them to the
checkoutlist file.

14.3.3.4. The config file
Repository configuration is specified in the config administrative file.
LockDir= dir
Directs CVS to put its lock files in the alternate directory given instead of in the repository itself,
allowing users without write access to the repository (but with write access to dir) to read from the
repository.

Version 1.10 doesn't support alternate directories for lock files and reports an error if this option is set.
Older versions of CVS (1.9 and older) don't support this option either and will not report an error. Do
not mix versions that support alternate directories for lock files with versions that don't, since lock files
in both places defeat the purpose of having them.

RCSBIN= dir
Obsolete (used in versions 1.9.12 to 1.9.18). This option used to tell CVS where to find RCS programs.
Since all RCS-related functions are now handled internally, this option does nothing.

SystemAuth= value
CVS tries to authenticate users via the CVSROOT/ passwd file first, and if that fails and this option is

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set to yes, CVS tries to authenticate via the system's user database. This option is used with the
password server. The default is yes.

TopLevelAdmin= value
If this option is set to yes, an additional CVS directory is created at the top-level directory when
checkout is run. This allows the client software to detect the repository locator in that directory (see
Section 14.4.1, "Repository Locators"). The default is no.

This option is useful if you check out multiple modules to the same sandbox directory. If it is enabled,
you won't have to provide a repository locator after the first checkout; CVS infers it from the
information in the top-level CVS directory created during the first checkout.

14.3.3.5. The cvsignore file
The cvsignore administrative file contains a list of filename patterns to ignore, just like the .cvsignore files
that can appear in sandboxes and user home directories. Unlike the filename patterns in other administrative
files, these patterns are in sh syntax; they are not GNU Emacs-style regular expressions. There can be
multiple patterns on a line, separated by whitespace (consequently, the patterns themselves cannot contain
whitespace).

Table 14-5 shows the most commonly used sh-style pattern constructs.

Table 14-5. Filename Patterns for cvsignore

Construct Description

? Any one character.
* Any sequence of zero or more characters.

Again, diverging from the standards used by the rest of the administrative files, the cvsignore file does not
support comments.

14.3.3.6. The cvswrappers file
While the cvsignore file allows CVS to ignore certain files, the cvswrappers file allows you to give CVS
default options for commands that work with files. Lines in this file consist of a sh-style filename pattern
followed by a -k (keyword substitution mode) option and/ or an -m (update method) option. The legal values
for -k are described in Table 14-19. The legal values for -m are COPY and MERGE.

If -m COPY is specified, CVS will not attempt to merge the files. Instead, it presents the user with conflicting
versions of the file, and he can choose one or the other or resolve the conflict manually.

For example, to treat all files ending in .exe as binary, add this line to the file:
*. exe -k b

14.3.3.7. The history file
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If this file exists, CVS inserts records of activity against the repository. This information produces displays of
the cvs history command. The history file is not intended for direct reading or writing by programs other than
CVS.

A repository set up with cvs init automatically has a history file.

14.3.3.8. The loginfo file
The loginfo administrative file works much like the commitinfo file and can use the special patterns ALL and
DEFAULT. This file allows you to do something with commit log messages and related information.

The programs called during loginfo processing receive the log message on standard input. Table 14-6 shows
the three codes that can pass additional information to the called programs via command-line arguments.

Table 14-6. Special loginfo Variables

Variable Description

s Filename
V Pre-commit revision number
v Post-commit revision number

If a percent sign (%) followed by the desired variable is placed after the command path, CVS inserts the
corresponding information as a whitespace-separated list with one entry for each file, preceded by the
repository path (as with commitinfo). There can be only one percent sign on the command line, so if you want
information from more than one variable, place the variable names inside curly brackets: %{...}. In this
case, each file-specific entry has one field for each variable, separated by commas. For example, the code
%{ sVv} expands into a list like this:

/usr/ local/ cvsrep/ hello Makefile, 1.1,1.2 hello. c, 1.8,1.9It can be helpful to send email notifications each time someone commits a file to the repository. Developers
can monitor this stream of notices to determine when they should pull the latest development code into their
private sandboxes. For example, consider a developer doing some preparatory work in his sandbox while he
awaits stabilization and addition of another developer's new library. As soon as the new library is added and
committed, email notification goes out, and the waiting developer sees the code is ready to use. So, he runs
cvs upd -d in the appropriate directory to pull in the new library code and then sets about integrating it with
his work.

It is simple to set up this kind of notification. Just add a line like this to the CVSROOT/ loginfo file:
DEFAULT mail -s %s developers@ company. comOften, the email address is a mailing list, which has all the interested parties (developers or otherwise) on the
distribution list. If you want to send messages to multiple email addresses, you can write a script to do that
and have that script called via this file. Alternatively, you can use the log. pl program that comes as part of the
CVS source distribution (located at /usr/ local/ src/ cvs-1.10.8/ contrib/ log. pl, assuming CVS was unpacked into

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/usr/ local/ src). Instructions for its use are provided as comments in the file.

14.3.3.9. The modules file
The top-level directories in a repository are called modules. In addition to these physical modules, CVS
provides a mechanism to create logical modules through the modules administrative file. Here are the three
kinds of logical modules:

Alias
Alias modules are defined by lines of the form:
module_ name -a alias_ module ...You can use the alias module name in CVS commands in the same way you use the modules named
after the -a option.

Regular
Regular modules are defined by lines of the form:
module_ name [options] directory file ...Checking out module_ name results in the specified files from directory being checked out into a
directory named module_ name. The intervening directories (if any) are not reflected in the sandbox.

Ampersand
Ampersand modules are defined by lines of the form:
module_ name [options] &other_ module ...Checking out such a module results in a directory named module_ name, which in turn contains copies
of the other_ module modules.

Table 14-7 shows the options that can define modules.

Table 14-7. Module Options

Option Description

-d name Overrides the default working directory name for the module
-e prog Runs the program prog when files are exported from the module; the module name is passed to prog as the sole argument

-i prog Runs the program prog when files are committed to the module; the repository directory of the committed files is passed in to prog as the sole argument

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-i prog Runs the program prog when files are checked out from the module; the module name is passed in to prog as the sole argument
-s status Assigns a status descriptor to the module
-t prog Runs the program prog when files are tagged in the module using rtag; the module name and the symbolic tag are passed to prog

-u prog Runs the program prog when files are updated in the module's top-level directory; the full path to the module within the repository is passed to prog as the sole argument

Alias modules provide alternative names for other modules or shortcuts for referring to collections or
subdirectories of other modules. Alias module definitions function like macro definitions in that they cause
commands to run as if the expanded list of modules and directories was on the command line. Alias modules
do not cause the modules of their definition to be grouped together under the alias name (use ampersand
modules for that). For example, the definition:

h -a hellomakes the name h a synonym for the hello module. This definition:
project -a library client serverallows you to check out all three modules of the project as a unit. If an entry in the definition of an alias
module is preceded by an exclamation point (!), then the named directory is excluded from the module.

Regular modules allow you to create modules that are subsets of other modules. For example, the definition:
header library library. hcreates a module that just contains the header file from the library module.
Ampersand modules are true logical modules. There are no top-level directories for them in the repository, but
you can check them out to sandboxes, and directories with their names will then appear. The modules listed in
the definition are below that directory. For example:

project &library &client &serveris almost the same as the alias module example given earlier, except that the submodules are checked out
inside a subdirectory named project.

In this file, long definitions may be split across multiple lines by terminating all but the last line with
backslashes (\).

14.3.3.10. The notify file
This file is used in conjunction with the watch command. When notifications are appropriate, this file is
consulted to determine how to do the notification.

Each line of the notify file contains a filename pattern and a command line. CVS's notification mechanism
uses the command line specified to perform notifications for files having names that match the corresponding

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pattern.

There is a single special-purpose variable, %s, that can appear in the command specification. When the
command is executed, the name of the user to notify replaces the variable name. If the users administrative
file exists, the user names are looked up there, and the resulting values are used for %s instead. This allows
emails to be sent to accounts other than those on the local machine. Details are sent to the notification
program via standard input.

Typical usage of this feature is the single entry:
ALL mail %s -s "CVS notification"In fact, this entry is present in the default notify file created when you run cvs init to create a repository
(although it is initially commented out).

14.3.3.11. The passwd file
If you access the repository via a pserver repository locator (see Section 14.4.1, "Repository Locators"), then
CVS can have its own private authentication information, separate from the system's user database. This
information is stored in the CVSROOT/ passwd administrative file.

This feature provides anonymous CVS access over the Internet. By creating an entry for a public user (usually
anoncvs or anonymous), the pserver can be used by many people sharing the public account. If you don't want
to create a system user with the same name as the public user, or if you have such a user but it has a different
purpose, you can employ a user alias to map it to something else:

anonymous: TY7QWpLw8bvus: cvsnonameThen, make sure you create the cvsnoname user on the system. You can use /bin/ false as the login shell and
the repository's root directory as the home directory for the user.

To restrict the public user to read-only access, list it in the CVSROOT/ readers administrative file.
Additionally, CVS's private user database is useful even if you don't want to set up anonymous CVS access.
You can restrict access to a subset of the system's users, provide remote access to users who don't have
general system access, or prevent a user's normal system password from being transmitted in the clear over
the network (see Section 14.3.2, "Security Issues").

There is no cvs passwd command for setting CVS-specific passwords (located in the repository file
CVSROOT/ passwd). CVS-specific user and password management are manual tasks.

14.3.3.12. The rcsinfo file
CVS consults this file when doing a commit or import to determine the log message editor template. Each
entry in the file consists of a filename pattern and the name of the file to use as the template for module
directories with matching names.

The ALL and DEFAULT special patterns apply to this file.

14.3.3.13. The readers file

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If this file exists, users listed in it have read-only access.
14.3.3.14. The taginfo file
CVS consults this file whenever the tag or rtag commands are used. Entries in this file are filename patterns
and program specifications. The ALL special pattern applies to this file.

The taginfo file is called with the tag, the operation being performed, the module directory name (relative to
the repository root), and the filename and revision number for each affected file. The valid operations are:
add (for tag), del (for tag -d), and mov (for tag -F).

If the taginfo program returns a nonzero status, the tag or rtag command that caused its execution is aborted.

14.3.3.15. The users file
If this file exists, it is consulted during processing of the notify administrative file's contents. Entries in this
file consist of two colon-separated fields on a single line. The first field is the name of a user, and the second
field is a value (normally the user's email address on another machine). For example:

john: john@ somecompany. com jane: jane@ anothercompany. com

14.3.3.16. The verifymsg file
CVS consults this file to determine if log messages should be validated. If the program returns a nonzero
status, the commit is aborted. The verifymsg file is called with the full path to a file containing the log
message to be verified.

The ALL special pattern is not supported for this file, although DEFAULT is. If more than one pattern
matches, the first match is used.

14.3.3.17. The writers file
If this file exists, users listed in it have read/ write access (unless they are also listed in the readers file, in
which case they have read-only access).

14.3.4. Hacking the Repository
Since the repository is a normal directory, albeit one with special contents, it is possible to cd into the
directory and examine its contents and/ or make changes to the files and directories there. For each file that has
been added there will be a file with the same name followed by ,v in a corresponding directory in the
repository. These are RCS (the format, not the program) files that contain multiple versions of the file.

NOTE
Since the activities discussed in this section involve making changes directly to the repository
instead of working through CVS commands, you should exercise extreme caution and have
current backups when following these instructions.

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14.3.4.1. Restructuring a project

Restructuring the project by moving files and directories around (and possibly renaming them) in the
repository will allow the files to retain their history. The standard way to rename a file when using CVS is to
rename the file in the sandbox and do a cvs remove on the old name and a cvs add on the new name. This
results in the file being disconnected from its history under the new name, so sometimes it is better to do the
renaming directly in the repository, although doing this while people have active sandboxes is dangerous,
since the sandboxes will contain information about a file that is no longer in the repository.

14.3.4.2. Bulk importing
When importing an entire project, all of the project's files will be added to the repository. But, if some of these
files shouldn't have been added, you'll want to remove them. Doing a cvs remove will accomplish this, but
copies of those files will remain in the repository's .Attic directory forever. To avoid this, you can delete the
files from the repository directly before checking out sandboxes from it.

14.3.5. Importing
If you have an existing code base, you'll want to import it into CVS in a way that preserves the most historical
information. This section provides instructions for importing projects into CVS from code snapshots or other
version control systems. All of these, except the code snapshot import procedure, are based upon conversion
to RCS files, followed by placing the RCS files in the proper location in the CVS repository.

14.3.5.1. Importing code snapshots
If you have maintained project history archives manually by taking periodic snapshots of the code, you can
import the first snapshot, tag it with the date or version number, and then successively overlay the updated
files from later archives. Each set can then be committed and tagged in order to bootstrap a repository that
maintains the prior history.

For example, first unpack the distributions (this assumes they unpack to directories containing the version
numbers):

user@ localhost$ tar xvzf foo-1.0. tar. gzuser@ localhost$ tar xvzf foo-1.1. tar. gzuser@ localhost$ tar xvzf foo-2.0. tar. gz

Next, make a copy of the first version, import it into the CVS repository, check it out to make a sandbox
(since importing doesn't convert the source directory into a sandbox), and use cvs tag to give it a symbolic
name reflecting the project version:

user@ localhost$ mkdir foouser@ localhost$ cp -R -p foo-1.0/* foouser@ localhost$ cd foouser@ localhost$ cvs import -m 'Imported version 1.0' foo vendor startuser@ localhost$ cd ..user@ localhost$ mv foo foo. bakuser@ localhost$ cvs checkout foouser@ localhost$ cd foouser@ localhost$ cvs tag foo-1_ 0user@ localhost$ cd ..

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Now, apply the differences between version 1.0 and 1.1 to the sandbox, commit the changes, and create a tag:
user@ localhost$ diff -Naur foo-1.0 foo-1.1 | (cd foo; patch -Np1)user@ localhost$ cd foouser@ localhost$ cvs commit -m 'Imported version 1.1'user@ localhost$ cvs tag foo-1_ 1user@ localhost$ cd ..

Now, apply the differences between version 1.1 and 2.0 to the sandbox, commit the changes, and create a tag:
user@ localhost$ diff -Naur foo-1.1 foo-2.0 | (cd foo; patch -Np1)user@ localhost$ cd foouser@ localhost$ cvs commit -m 'Imported version 2.0'user@ localhost$ cvs tag foo-2_ 0

Now, you can use the log command to view the history of the files, browse past versions of the files, and
continue development under version control.

14.3.5.2. Importing from RCS
If you are migrating from RCS to CVS, following these instructions will result in a usable CVS repository.
This procedure involves direct modification of the CVS repository, so it should be undertaken with caution.

Before beginning, make sure none of the files to be imported into CVS are locked by RCS. Then, create a new
CVS repository and module (or a new module within an existing repository). Next, create directories in the
CVS repository to mirror the project's directory structure. Finally, copy all the version files (, v) from the
project (which may be in RCS subdirectories) into the appropriate directories in the repository (without RCS
subdirectories).

For example, first move aside the directory under RCS control, create an empty directory to build the new
CVS structure, import the directory, and then check it out to make a sandbox:

user@ localhost$ mv foo foo-rcsuser@ localhost$ mkdir foouser@ localhost$ cd foouser@ localhost$ cvs import -m 'New empty project' foo vendor startuser@ localhost$ cd ..user@ localhost$ mv foo foo. bakuser@ localhost$ cvs checkout foo

Next, make directories and add them to the repository to match the structure in the RCS project:
user@ localhost$ cd foouser@ localhost$ mkdir diruser@ localhost$ cvs add diruser@ localhost$ cd ..

Now, copy the ,v files from the RCS project into the repository for the CVS project:
user@ localhost$ cp -p foo-rcs/*, v $CVSROOT/ foo

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user@ localhost$ cp -p foo-rcs/ dir/*, v $CVSROOT/ foo/ dir

Finally, issue the cvs update command in the sandbox directory to bring in the latest versions of all the files:
user@ localhost$ cd foouser@ localhost$ cvs upd

14.3.5.3. Importing from SCCS
To import from SCCS, use the sccs2rcs script located in the contrib directory of the CVS distribution to
convert the files to RCS format, and then follow the preceding RCS procedure. You must have both CVS and
SCCS installed for this to work. The script's comments contain additional instructions.

14.3.5.4. Importing from PVCS
To import from PVCS, use the pvcs_ to_ rcs script located in the contrib directory of the CVS distribution to
convert the files to RCS format, and then follow the previous RCS procedure. You must have both CVS and
PVCS installed for this to work. The script's comments contain additional instructions.

14.3.6. Using an Interim Shared Sandbox
Sometimes projects will develop unintended environmental dependencies over time, especially when there is
no pressure for the code to be relocatable. A project developed outside version control may even be initially
developed in place (at its intended installation location). While these practices are not recommended, they do
occur in real-world situations; CVS can be helpful in improving the situation, by encouraging relocatability
from the beginning of a project.

The default mode of operation for CVS is multiple independent sandboxes, all coordinated with a central
shared repository. Code that runs in this environment is necessarily (at least partially) relocatable. So, using
CVS from the beginning of a project helps ensure flexibility.

However, if a project is already well underway, an interim approach can be used. For example, you could
convert the development area to a single shared sandbox by importing the code into CVS and checking it back
out again:

user@ localhost$ cd /usr/ local/ baruser@ localhost$ cvs import bar vendor startuser@ localhost$ cd ..user@ localhost$ mv bar bar. bakuser@ localhost$ cvs checkout bar

Chances are good that this approach is too aggressive and will check in more files than absolutely necessary.
You can either go back and hack the repository to remove the files that shouldn't be there or just issue the cvs
remove command to delete them as you discover them.

In addition, there will probably be some binary files in the sandbox that were imported as text files. Wherever
you see a binary file that needs to remain in the repository, you should issue the command cvs admin -kb file,
then make a fresh copy from the project backup. Finally, issue the command cvs commit file to commit the
fixed file back to the repository.

Having version control in place before making flexibility enhancements is a good idea, since it makes it easier
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to find (and possibly reverse) changes that cause trouble.

The repository locator (see Section 14.4.1, "Repository Locators") is specified via the -d option or the
$CVSROOT environment variable. It is stored in the various sandbox CVS/ root files. If you are using the
password server (pserver), the user ID of the person checking out the sandbox will be remembered. If more
than one person is working with a particular sandbox, they will have to share an account for CVS access.

One way to do this is to have a neutral user account, with a password known by everyone with CVS access.
Everyone can then issue the cvs login command with the same user ID and password and have access to the
repository. Once you are no longer using a shared sandbox, this workaround won't be necessary. However,
during the time you are using a shared sandbox, it is important that the developers type their real user IDs into
their log messages, since all the changes will appear to be made by the common user.

14.3.7. Global Server Option
The server has one global option: --allow-root= rootdir. This option is used to tell the CVS server to accept
and process requests for the specified repository.

14.3.8. Administrator Commands
Table 14-8 lists the commands that CVS administrators can use to manage their repositories.

Table 14-8. Administrator Commands

Command Description

admin
adm
rcs
Perform administrative functions

init Create a new repository
server Run in server mode

14.3.8.1. admin
admin [ -b[rev] ] [ -cstring ] [ -kkflag ] [ -l[rev] ] [ -L ] [ -mrev:msg ] [ -nname[:[rev]] ] [ -Nname[:[rev]] ] [ -orange ] [ -q ]

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[ -sstate[: rev][ -t[ file] ] [ -t-string ] [ -u[rev] ] [ -U ] [files ... ]

The admin is used to perform administrative functions. If a cvsadmin user group exists, then only those users
in that group will be able to run admin with options other than -k. Additional options that may be used with
the admin command are listed in Table 14-9.

Table 14-9. admin Options

Option Description

-b[ rev] Set the default branch.
-cstring Obsolete. Set the comment leader.
-kkflag Set the default keyword substitution mode.
-l[ rev] Lock the specified revision.
-L Enable strict locking.
-mrev: msg Change the revision's log message.
-nname[:[ rev]] Give the branch or revision specified the symbolic name name.
-Nname[:[ rev]] The same as -n, except that if name is already in use, it is moved.
-orange Delete revisions permanently.
-q Don't print diagnostics.
-sstate[: rev] Change the state of a revision.
-t[ file] Set the descriptive text in the RCS file.
-t-string Set the descriptive text in the RCS file to string.
-u[ rev] Unlock the specified revision.
-U Disable strict locking.

If the revision specified for -l is a branch, the latest revision on that branch will be used. If no revision is
given, the latest revision on the default branch is used.

If the name given for -n is already in use, an error is generated. You can use -N to move a tag (change the
revision associated with the tag); however, you should usually use cvs tag or cvs rtag instead.

The -o option is very dangerous and results in a permanent loss of information from the repository. Use it with
extreme caution and only after careful consideration. See Table 14-10 for the various ways to specify ranges.

There must not be any branches or locks on the revisions to be removed. Beware of interactions between this

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command and symbolic names.

If no file is specified to the -t option, CVS reads from standard input until it reaches the end of the file or a
period on a line by itself.

The determination of the target revision for the -u option is the same as for -l.
Table 14-10. Range Formats

Format Description

rev1:: rev2 Eliminate versions between rev1 and rev2, retaining only enough information to go directly from rev1 to rev2. The two specified versions are retained.
:: rev The same as rev1:: rev2, except the first revision is the branchpoint revision.
rev:: The same as rev1:: rev2, except the second revision is the end of the branch, and it is deleted instead of retained.
rev Delete the specified revision.
rev1: rev2 The same as rev1:: rev2, except the two named revisions are deleted as well.
:rev The same as :: rev2, except the named revision is deleted as well.
rev: The same as rev1::, except the named revision is deleted as well.

The options in Table 14-11 are present in CVS for historical reasons and should not be used (using these
options may corrupt the repository).

Table 14-11. Obsolete admin Options

Option Description

-alogins Append the logins to the RCS file's access list.
-Aoldfile Append the access list of oldfile to the access list of the RCS file.
-e[ logins] Erases logins from the RCS file's access list, or erases all if a list is not provided.

-i Create and initialize a new RCS file. Don't use this option. Instead, use add to add files to a CVS repository.

-I Run interactively. This option doesn't work with client/ server CVS and is likely to be removed in a future version.
-Vn Obsolete. This option was used to specify that the RCS files used by CVS should be made compatible with a specific version of RCS.
-xsuffixes This option used to be described as determining the filename suffix for RCS files, but CVS has always only used ,v as the RCS file suffix.

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14.3.8.2. init

initInitializes the repository. Use the global -d option to specify the repository's directory if $CVSROOT isn't set
appropriately.

The newly initialized repository will contain a CVSROOT module, but nothing else. Once the repository is
initialized, use other CVS commands to add files to it or to check out the CVSROOT module to make changes
to the administrative files.

14.3.8.3. pserver
pserverOperate as a server, providing access to the repositories specified before the command with the --allow-root
option. This command is used in the inetd. conf file, not on the command line. Another global option
frequently used with this command is -T (see Table 14-1).

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14.4. CVS User Reference
This section provides details on connecting to a repository, the structure of sandboxes, and using
the CVS commands.

14.4.1. Repository Locators
CVS currently supports five methods for the client to access the repository: local, external, a
password server, a GSS-API (Generic Security Services API) server, and a Kerberos 4 server
(most Kerberos users will want to use GSS-API). Table 14-12 describes the various repository

locator types and their respective access methods.

Table 14-12. Repository Access Types and Methods

Method Locator Format Description

Local path
If the repository directory is local to the
computer from which you will access it (or
appears local, such as an NFS or Samba
mounted filesystem), the repository string is
just the pathname of the repository
directory, such as /usr/ local/ cvsrep.

External :ext: user@ host: path
External repositories are accessed via a
remote shell utility, usually rsh (the
default) or ssh. The environment variable
$CVS_ RSH is used to specify the remote
shell program.

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Password server :pserver: user@ host: path
Password server repositories require
authentication to a user account before
allowing use of the repository. Public CVS
servers are commonly configured this way
so they can provide anonymous CVS
access. See Section 14.3.3.11, "The passwd

file", earlier in this chapter, for more
information on anonymous CVS.

GSS-API server :gserver:This locator type is used for servers
accessible via Kerberos 5 or other
authentication mechanisms supported by
GSS-API.

Kerberos server :kserver: This locator type is used for servers accessible via Kerberos 4.

14.4.2. Configuring CVS
CVS's behavior can be influenced by two classes of settings other than the command-line
arguments: the environment variables (see Table 14-13) and special files (see Table 14-14).

Table 14-13. Environment Variables

Variable Description

$COMSPEC Command interpreter on OS/ 2, if not cmd. exe.

$CVS_ CLIENT_ LOGClient-side debugging file specification for client/ server
connections.

$CVS_ CLIENT_ LOG is the basename for the
$CVS_ CLIENT_ LOG. in and $CVS_ CLIENT_ LOG. out
files, which will be written in the current working
directory at the time a command is executed.

$CVS_ CLIENT_ PORT $CVS_ IGNORE_ REMOTE_ ROOT

The port number for :kserver: locators.
$CVS_ CLIENT_ PORT doesn't need to be set if the
kserver is listening on port 1999 (the default).

According to the ChangeLog, this variable was removed
from CVS with Version 1.10.3.

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$CVS_ PASSFILE Password file for :PSERVER: locators. This variable must be set before issuing the cvs login to have the
desired effect. Defaults to $HOME/. cvspass.

$CVS_ RCMD_ PORT For non-Unix clients, the port for connecting to the
server's rcmd daemon.

$CVS_ RSH Remote shell for :ext: locators, if not rsh.

$CVS_ SERVER Remote server program for :ext: locators, if not cvs.
$CVS_ SERVER_ SLEEP Server-side execution delay (in seconds) to allow time to
attach a debugger.

$CVSEDITOR Editor used for log messages; overrides $EDITOR.

$CVSIGNORE A list of filename patterns to ignore, separated by white space. (See also cvsignore in Table 14-4 and .cvsignore
in Table 14-14.)

$CVSREAD Determines read-only (if the variable is set) or read/ write
(if the variable is not set) for checkout and update.

$CVSROOT Default repository locator.

$CVSUMASK Used to determine permissions for (local) repository
files.

$CVSWRAPPERS A list of filename patterns for the cvswrappers function.
See also Section 14.3.3, "Repository Structure".

$EDITOR Specifies the editor to use for log messages; see notes for
$CVSEDITOR earlier in this table.

$HOME On Unix, used to find the .cvsrc file.

$HOMEDRIVE On Windows NT, used to find the .cvsrc file.
$HOMEPATH On Windows NT, used to find the .cvsrc file.
$PATH Used to locate programs to run.

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$RCSBIN Used to locate RCS programs to run. This variable is
obsolete.

$TEMP

$TMP $TMPDIR

Location for temporary files. $TMPDIR is used by the
server. On Unix, /tmp (and TMP on Windows NT) may
not be overridden for some functions of CVS due to
reliance on the system's tmpnam() function.

Despite the similarity in names, the $CVSROOT environment variable and the CVSROOT
directory in a repository are not related to each other.

The "RSH" in the name of the $CVS_ RSH environment variable doesn't refer to the particular
program (rsh), but rather to the program CVS is supposed to use for creating remote shell
connections (which could be some program other than rsh, such as ssh).

Since there is only one way to specify the remote shell program to use ($ CVS_ RSH), and since
this is a global setting, users that commonly access multiple repositories may need to pay close
attention to which repository they are using. If one repository requires one setting of this
variable and another requires a different setting, then you will have to change this variable
between accesses to repositories requiring different settings. This aspect of the repository access
method is not stored in the CVS/ Root file in the sandbox (see Section 14.4.4.3, "CVS

directories", later in this chapter). For example, if you access some repositories via rsh and some
via ssh, then you can create the following two utility aliases (bash syntax):

user@ localhost$ alias cvs=" export CVS_ RSH= ssh; cvs"user@ localhost$ alias cvr=" export CVS_ RSH= rsh; cvs"

Table 14-14 shows the files used by the CVS command-line client for server connection and
client configuration information. These files reside in the user's home directory.

Table 14-14. Client Configuration Files

Option Description

~/. cvsignore Filename patterns of files to ignore
~/. cvspass Passwords cached by cvs login

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~/. cvsrc Default command options

~/. cvswrappers User-specific checkout and commit filters

The ~/. cvspass file is really an operational file, not a configuration file. It is used by the cvs
client program to store the repository user account password between cvs login and cvs logoff.

Some common .cvsrc settings are:
update -dP
Brings in new directories and prunes empty directories on cvs update.
diff -c
Give output in context diff format.

14.4.3. Creating a Sandbox
In order to use CVS, you must create a sandbox or have one created for you. This section
describes sandbox creation, assuming there is already a module in the repository you want to
work with. See Section 14.4.7.11, "import" for information on importing a new module into the

repository.

1. Determine the repository locator. Talk to the repository administrator if you need help
finding the repository or getting the locator syntax right.
2. If this will be the main repository you use, set $CVSROOT; otherwise, use the -d option
when running CVS commands that don't infer the repository from the sandbox files.
3. Pick a module to check out.
4. Pick a sandbox location, and cd to the parent directory.
5. If the repository requires login, do cvs login.
6. Run cvs checkout module.

For example:
export CVSROOT=/ usr/ local/ cvsroot cd ~/ work cvs checkout hello

14.4.4. Sandbox Structure
This section describes the files and directories that may be encountered in sandboxes.

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14.4.4.1. .cvsignore files
Sandboxes may contain .cvsignore files. These files specify filename patterns for files that may
exist in the sandbox but which normally won't be checked into CVS. This is commonly used to
cause CVS to bypass derived files.

14.4.4.2. .cvswrappers files
Sandboxes may contain .cvswrappers files, which provide directory-specific file handling
information like that in the repository configuration file cvswrappers (see Section 14.3.3.6, "The

cvswrappers file", earlier in this chapter).

14.4.4.3. CVS directories
Each directory in a sandbox contains a CVS directory. The files in this directory (see Table 14-
15) contain metadata used by CVS to locate the repository and track which file versions have
been copied into the sandbox.

Table 14-15. Files in the CVS Directories

File Description

Base
Baserev
Baserev. tmp

The Base directory stores copies of files when the edit command is in use.
The Baserev file contains the revision numbers of the files in Base. The
Baserev. tmp file is used in updating the Baserev file.

Checkin. prog
Update. prog
The programs specified in the modules file for options -i and -u,
respectively (if any).

Entries Version numbers and timestamps for the files as they were copied from the
repository when checked out or updated.

Entries. Backup

Entries. Log
Entries. Static
These are temporary and intermediate files used by CVS.

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Notify
Notify. tmp
These are temporary files used by CVS for dealing with notifications for
commands like edit and unedit.

Repository The name by which the directory is known in the repository.
Root The repository locator in effect when the sandbox was created (via cvs
checkout).

Tag Information about sticky tags and dates for files in the directory.

Template Used to store the contents of the rcsinfo administrative file from the
repository for remote repositories.

Since each sandbox directory has one CVS/ Root file, a sandbox directory corresponds to exactly
one repository. You cannot check out some files from one repository and some from another into
a single sandbox directory.

14.4.5. Client Global Options
Table 14-16 lists the global options that control the operation of the CVS client program.

Table 14-16. Client Global Options

Option Description

-a Authenticate (gserver only).
-d root Locate the repository. Overrides the setting of $CVSROOT.

-e editor Specify message editor. Overrides the settings of $CVSEDITOR and $EDITOR.

-f Don't read ~/. cvsrc. Useful when you have .cvsrc settings that you want to forgo for a particular command.
-H [command]
--help [command]
Display help. If no command is specified, general CVS help, including a
list of other help options, is displayed.

-l Don't log command in history.

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-n Don't change any files. Useful when you want to know ahead of time which files will be affected by a particular command.
-q Be quiet.
-Q Be very quiet. Print messages only for serious problems.
-r Make new working files read-only.

-s variable= value Set the value of a user variable to a given value. User variables can be used in the contents of administrative files.

-t
Trace execution. Helpful in debugging remote repository connection
problems and, in conjunction with -n, in determining the effect of an
unfamiliar command.

-w Make new working files read/ write. Overrides $CVSREAD. Files are read/ write unless $CVSREAD is set or -r is specified.
-x Encrypt. (Introduced in Version 1.10.)
-z gzip_ level Set the compression level. Useful when using CVS in client/ server mode across slow connections.

14.4.6. Common Client Options
Table 14-17 and Table 14-18 describe the options that are common to many CVS commands.
Table 14-17 lists the common options with a description of their function, while Table 14-18
lists which options can be used with the user commands. In the sections that follow, details will
be provided only for options that are not listed here and for those that do not function as
described here.

Table 14-17. Common Options

Option Description

-D date Use the most recent revision no later than date.
-f
For commands that involve tags (via -r) or dates (via -D), include files not tagged
with the specified tag or not present on the specified date. The most recent revision
will be included.

-k kflag Determine how keyword substitution will be performed. The space between -k and kflag is optional. See Table 14-19 for the list of keyword substitution modes.
-l Do not recurse into subdirectories.

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-n Don't run module programs.
-R Do recurse into subdirectories (the default).
-r rev Use a particular revision number or symbolic tag.

Table 14-18 shows which common options are applicable to each user command.
Table 14-18. Client Common Option Applicability

User Command -D -f -k -l -n -R -r

add
annotate
checkout
commit
diff
edit
editors
export
help
history
import
log
login
logout
rdiff
release
remove
rtag
status

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tag
unedit
update
watch
watchers

14.4.6.1. Date formats
CVS can understand dates in a wide variety of formats, including:
ISO standard
The preferred format is YYYY-MM-DD HH: MM, which would read as 2000-05-17, or
2000-05-17 22: 00. The technical details of the format are defined in the ISO 8601
standard.

Email standard
17 May 2000. The technical details of the format are defined in the RFC 822 and RFC
1123 standards.

Relative
10 days ago, 4 years ago.Common
month/ day/ year. This form can cause confusion because not all cultures use the first two
fields in this order (1/ 2/ 2000 would be ambiguous).

Other
Other formats are accepted, including YYYY/ MM/ DD and those omitting the year (which
is assumed to be the current year).

14.4.6.2. Keyword substitutions
Table 14-19 describes the keyword substitution modes that can be selected with the -k option.
CVS uses keyword substitutions to insert revision information into files when they are checked
out or updated.

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Table 14-19. Keyword Substitution Modes

Mode Description

b Binary mode. Treat the file the same as with mode o, but also avoid newline conversion.
kKeyword-only mode. Flatten all keywords to just the keyword name. Use this mode if
you want to compare two revisions of a file without seeing the keyword substitution
differences.

kv Keyword-value mode. The keyword and the corresponding value are substituted. This is the default mode.

kvlKeyword-value-locker mode. This mode is the same as kv mode, except it always
adds the lock holder's user ID if the revision is locked. The lock is obtained via the
cvs admin -l command.

o Old-contents mode. Use the keyword values as they appear in the repository rather than generate new values.

vValue-only mode. Substitute the value of each keyword for the entire keyword field,
omitting even the $ delimiters. This mode destroys the field in the process, so use it
cautiously.

Keyword substitution fields are strings of the form $Keyword ...$. The valid keywords are:
AuthorThe user ID of the person who committed the revision.
DateThe date and time (in standard UTC format) the revision was committed.
HeaderThe full path of the repository RCS file, the revision number, the commit date, time, and
user ID, the file's state, and the lock holder's user ID if the file is locked.

IdA shorter form of Header, omitting the leading directory name( s) from the RCS file's
path, leaving only the filename.

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Name

The tag name used to retrieve the file, or empty if the no explicit tag was given when the
file was retrieved.

LockerThe user ID of the user holding a lock on the file, or empty if the file is not locked.
LogThe RCS filename. In addition to keyword expansion in the keyword field, each commit
adds additional lines in the file immediately following the line containing this keyword.
The first such line contains the revision number, the commit date, time, and user ID.
Subsequent lines are the contents of the commit log message. The result over time is a
reverse-chronological list of log entries for the file. Each of the additional lines is
preceded by the same characters that precede the keyword field on its line. This allows
the log information to be formatted in a comment for most languages. For example:

# # ch14_ 04. htm # # $Log: ch14_ 04. htm, v $ # Revision 1.3 2001/ 06/ 22 16: 14: 09 ellie # replaced grave entity w/ literal backtic # # Revision 1.2 2001/ 06/ 18 18: 28: 37 ellie # regenerated after xslt fixes # # Revision 1.1 2000/ 06/ 09 18: 07: 51 ellie # Fixed the last remaining bug in the system. #

Be sure that you don't place any keyword fields in your log messages if you use this keyword,
since they will get expanded if you do.

RCSfileThe name of the RCS file (without any leading directories).
RevisionThe revision number of the file.
Source

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The full path of the RCS file.

StateThe file's state, as assigned by cvs admin -s (if you don't set the state explicitly, it will be
Exp by default).

14.4.7. User Commands
The CVS client program provides the user commands defined in Table 14-20.

Table 14-20. User Commands

Command Description

ad
add
new
Indicate that files/ directories should be added to the repository.

ann
annotate
Display contents of the head revision of a file, annotated with the revision
number, user, and date of the last change for each line.

checkout
co
get
Create a sandbox for a module.

ci
com
commit
Commit changes from the sandbox back to the repository.

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di
dif
diff
View differences between file versions.

edit Prepare to edit files. This is used for enhanced developer coordination.
editors Display a list of users working on the files. This is used for enhanced developer coordination.
ex
exp
export
Retrieve a module, but don't make the result a sandbox.

help Get help.
hi

his
history
Display the log information for files.

im
imp
import
Import new modules into the repository.

lgn
login
logon
Log in to (cache the password for) a remote CVS server.

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lo
log
rlog
Show the activity log for the file( s).

logout Log off from (flush the password for) a remote CVS server.
pa

patch
rdiff
Release diff. The output is the format of input to Larry Wall's patch command.
Does not have to be run from within a sandbox.

re
rel
release
p Perform a logged delete on a sandbox.

remove
rm
delete
Remove a file or directory from the repository.

rt
rtag
rfreeze
Tag a particular revision.

st
stat
status
Show detailed status for files.

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ta
tag
freeze
Attach a tag to files in the repository.

unedit Abandon file modifications and make read-only again.
up

upd
update
Synchronize sandbox to repository.

watch Manage the watch settings. This is used for enhanced developer coordination.
watchers Display the list of users watching for changes to the files. This is used for enhanced developer coordination.

14.4.7.1. add
add [ -kkflag ] [ -mmessage ]file ...

Indicate that files/ directories should be added to the repository. They are not actually added until
they are committed via cvs commit. This command is also used to resurrect files that have been
deleted with cvs remove.

The standard meaning of the common client option -k applies. There is only one additional
option that can be used with the add command: -m message. This option is used to provide a
description of the file (which appears in the output of the log command).

14.4.7.2. annotate
annotate [ [ -Ddate | -r rev ] -f ] [ -l | -R ]file ...

CVS prints a report showing each line of the specified file. Each line is prefixed by information
about the most recent change to the line, including the revision number, the user, and the date. If

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no revision is specified, then the head of the trunk is used.

The standard meanings of the common client options -D, -f, -l, -r, and -R apply.

14.4.7.3. checkout
checkout [ -A ] [ -c | -s ] [ -ddir [ -N ] ] [ [ -Ddate | -r rev ] -f ] [ -jrev1 [ -j rev2 ] ] [ -kkflag ] [ -l | -R ] [ -n ] [ -p ] [ -P ]module ...

Copy files from the repository to the sandbox.
The standard meanings of the common client options -D, -f, -k, -l, -r, and -R apply. Additional
options are listed in Table 14-21.

Table 14-21. Checkout Options

Option Description

-A Reset any sticky tags or dates.
-c Copy the module file to standard output.
-d dir Override the default directory name.
-j rev Join branches together.
-N Don't shorten module paths.

-p Pipe the files to standard output, with header lines between them showing the filename, RCS filename, and version.
-P Prune empty directories.
-s Show status for each module from the modules file.

14.4.7.4. commit
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commit [ -f | [ -l | -R ] ] [ -Ffile | -m message ] [ -n ] [ -rrevision ] [files ... ]

Commit the changes made to files in the sandbox to the repository.
The standard meanings of the common client options -l, -n, -r, and -R apply. Additional options
are listed in Table 14-22.

Table 14-22. commit Options

Option Description
-f Force commit, even if no changes were made.
-F file Use the contents of the file as the message.
-m message Use the message specified.

Use of the -r option causes the revision to be sticky, requiring the use of admin -A to continue
to use the sandbox.

14.4.7.5. diff
diff [ -kkflag ] [ -l | -R ] [ format ] [ [ -rrev1 | -D date1 ] [ -r rev2 | -D date2 ] ] [file ... ]

The diff command compares two versions of a file and displays the differences in a format
determined by the options. By default, the sandbox version of the file will be compared to the
repository version it was originally copied from.

The standard meanings of the common client options -D, -k, -l, -r, and -R apply. All options for
the diff command in Chapter 3, "Linux Commands" can also be used.

14.4.7.6. edit
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[ -a action ] [ -l | -R ] [file ... ]

The edit command is used in conjunction with watch to permit a more coordinated (serialized)
development process. It makes the file writable and sends out an advisory to any users who have
requested them. A temporary watch is established and will be removed automatically when
either the unedit or the commit command is issued.

The standard meanings of the common client options -l and -R apply. There is only one
additional option that can be used with the edit command: -a actions. This option is used to
specify the actions to watch. The legal values for actions are described in the entry for the watch
command.

14.4.7.7. editors
editors [ -l | -R ] [file ... ]

Display a list of users working on the files specified. This is determined by checking which users
have run the edit command on those files. If the edit command has not been used, no results will
be displayed.

The standard meanings of the common client options -l and -R apply.
See also the later section on watch.

14.4.7.8. export
export [ -ddir [ -N ] ] [ -Ddate | -r rev ] [ -f ] [ -kkflag ] [ -l | -R ] [ -n ] [ -P ]module ...

Export files from the repository, much like the checkout command, except that the result is not a
sandbox (i. e., CVS subdirectories are not created). This can be used to prepare a directory for
distribution. For example:

user@ localhost$ cvs export -r foo-1_ 0 -d foo-1.0 foo

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user@ localhost$ tar czf foo-1.0. tar. gz foo-1.0

The standard meanings of the common client options -D, -f, -k, -l, -n, -r, and -R apply.
Additional options are listed in Table 14-23.

Table 14-23. export Options

Option Description

-d dir Use dir as the directory name instead of using the module name.
-n Don't run any checkout programs.
-N Don't shorten paths.

When checking out a single file located one or more directories down in a module's directory
structure, the -N option can be used with -d to prevent the creation of intermediate directories.

14.4.7.9. help
helpDisplay helpful information about using the cvs program.

14.4.7.10. history
history [ -a | -uuser ] [ -bstring ] [ -c ] [ -Ddate ] [ -e | -xtype ] [ -f file | -mmodule | -n module | -p repository ]... [ -l ] [ -o ] [ -rrev ] [ -ttag ] [ -T ] [ -w ] [ -zzone ] [file ... ]

Display historical information. To use the history command, you must first set up the history
file in the repository. See Section 14.3.3, "Repository Structure" for more information on this

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file.

NOTE
When used with the history command, the functions of -f, -l, -n, and -p are not
the same as elsewhere in CVS.

The standard meanings of the common client options -D, and -r apply. History is reported for
activity subsequent to the date or revision indicated. Additional options are listed in Table 14-24.

Table 14-24. history Options

Option Description

-a Show history for all users (default is current user).
-b str Show history back to the first record containing str in the module name, filename, or repository path.
-c Report each commit.
-e Report everything.
-f file Show the most recent event for file.
-l Show last event only.
-m module Produce a full report on module.
-n module Report the last event for module.
-o Report on modules that have been checked out.
-p repository Show history for a particular repository directory.
-t tag Show history since the tag tag was last added to the history file.
-T Report on all tags.
-u name Show history for a particular user.
-w Show history only for the current working directory.
-w zone Display times according to the time zone zone.
-x type Report on specific types of activity. See Table 14-25.

The -p option should limit the history report to entries for the directory or directories (if
multiple -p options are specified) given, but as of Version 1.10.8, it doesn't seem to affect the

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output. For example, to report history for the CVSROOT and hello modules, run the command:

cvs history -p CVSROOT -p helloUsing -t is faster than using -r because it only needs to search through the history file, not all of
the RCS files.

The record types shown in Table 14-25 are generated by update commands.

Table 14-25. Update-Related history Record Types

Type Description

C Merge was necessary, but conflicts requiring manual intervention occurred.
G Successful automatic merge.
U Working file copied from repository.
W Working copy deleted.

The record types shown in Table 14-26 are generated by commit commands:
Table 14-26. Commit-Related history Record Types

Type Description

A Added for the first time
M Modified
R Removed

Each of the record types shown in Table 14-27 is generated by a different command.
Table 14-27. Other history Record Types

Type Command

E export
F release

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O checkout
T rtag

14.4.7.11. import
import [ -bbranch ] [ -d ] [ -Ipattern ] [ -kkflag ] [ -mmessage ] [ -Wspec ]module vendor_ tag release_ tag...

Import an entire directory into the repository as a new module. Used to incorporate code from
outside sources or other code that was initially created outside the control of the CVS repository.
More than one release_ tag may be specified, in which case multiple symbolic tags will be
created for the initial revision.

The standard meaning of the common client option -k applies. Additional options are listed in
Table 14-28.

Table 14-28. import Options

Option Description

-b branch Import to a vendor branch.
-d Use the modification date and time of the file instead of the current date and time as the import date and time. For local repository locators only.
-I pattern Filename patterns for files to ignore.
-m message Use message as the log message instead of invoking the editor.
-W spec Wrapper specification.

The -k setting will apply only to those files imported during this execution of the command. The
keyword substitution modes of files already in the repository are not modified.

When used with -W, the spec variable is in the same format as entries in the cvswrappers

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administrative file (see Section 14.3.3.6, "The cvswrappers file").

Table 14-29 describes the status codes displayed by the import command.
Table 14-29. import Status Codes

Status Description

C Changed. The file is in the repository, and the sandbox version is different; a merge is required.
I Ignored. The .cvsignore file is causing CVS to ignore the file.
L Link. Symbolic links are ignored by CVS.
N New. The file is new. It has been added to the repository.
U Update. The file is in the repository, and the sandbox version is not different.

14.4.7.12. log
log [ -b ] [ -ddates ] [ -h ] [ -N ] [ -rrevisions ] [ -R ] [ -sstate ] [ -t ] [ -wlogins ] [file ... ]

Print an activity log for the files.
The standard meaning of the common client option -l applies. Additional options are listed in
Table 14-30.

Table 14-30. log Options

Option Description

-b List revisions on default branch.
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-d dates Report on these dates.
-h Print header only.
-N Don't print tags.

-r[ revisions] Report on the listed revisions. There is no space between -r and its argument. Without an argument, the latest revision of the default branch is used.

-R Print RCS filename only. The usage of -R here is different than elsewhere in CVS (-R usually causes CVS to operate recursively).
-s state Print only those revisions having the specified state.
-t Print only header and descriptive text.

-wlogins Report on checkins by the listed logins. There is no space between -w and its argument.

For -d, use the date specifications in Table 14-31. Multiple specifications separated by
semicolons may be provided.

Table 14-31. log Date Range Specifications

Specification Description

d1< d2, or d2> d1 The revisions dated between d1 and d2, exclusive
d1<= d2, or d2>= d1 The revisions dated between d1 and d2, inclusive
<d, or d> The revisions dated before d
<= d, or d>= The revisions dated on or before d
d<, or >d The revisions dated after d
d<=, or >= d The revisions dated on or after d
d The most recent revision dated d or earlier

For -r, use the revision specifications in Table 14-32.
Table 14-32. log Revision Specifications

Specification Description

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rev1: rev2 The revisions between rev1 and rev2, inclusive.
:rev The revisions from the beginning of the branch to rev, inclusive.
rev: The revisions from rev to the end of the branch, inclusive.
branch All revisions on the branch.
branch1: branch2 All revisions on all branches between branch1 and branch2 inclusive.
branch. The latest revision on the branch.

For rev1: rev2, it is an error if the revisions are not on the same branch.
14.4.7.13. login
loginThis command is used to log in to remote repositories. The password entered will be cached in
the ~/. cvspass file, since a connection to the server is not maintained across invocations.

14.4.7.14. logout
logoutThis command logs out of a remote repository. The password cached in the ~/. cvspass file will
be deleted.

14.4.7.15. rdiff
rdiff [ -c | -s | -u ] [ { { -Ddate1 | -r rev1 } [ -D date2 | -r rev2 ] } | -t ] [ -f ] [ -l | -R ] [-Vvn] file...

The rdiff command creates a patch file that can be used to convert a directory containing one
release into a different release.

The standard meanings of the common client options -D, -f, -l, -r, and -R apply. Additional
options are listed in Table 14-33.

Table 14-33. rdiff Options

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Option Description

-c Use context diff format (the default).
-s Output a summary of changed files instead of a patch file.
-t Show the differences between the two most recent revisions.
-u Use unidiff format.

-V rcsver Obsolete. Used to specify version of RCS to emulate for keyword expansion. (Keyword expansion emulates RCS Version 5.)

14.4.7.16. release
release [ -d ]directory ...

Sandboxes can be abandoned or deleted without using cvs release if desired; using the release
command will log an entry to the history file (if this mechanism is configured) about the
sandbox being destroyed. In addition, it will check the disposition (recursively) of each of the
sandbox files before deleting anything. This can help prevent destroying work that has not yet
been committed.

There is only one option that can be used with the release command, -d. The -d option will
delete the sandbox copy if no uncommitted changes are present.

NOTE
New directories (including any files in them) in the sandbox will be deleted if the -d
option is used with release.

The status codes listed in Table 14-34 are used to describe the disposition of each file
encountered in the repository and the sandbox.

Table 14-34. release Status Codes.

Status Description

A The sandbox file has been added (the file was created and cvs add was run), but the addition has not been committed.

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M The sandbox copy of the file has been modified.
P

UUpdate available. There is a newer version of the file in the repository, and the copy
in the sandbox has not been modified.

R The sandbox copy was removed (the file was deleted and cvs remove was run), but the removal was not committed.
? The file is present in the sandbox but not in the repository.

14.4.7.17. remove
remove [ -f ] [ -l | -R ] [file ... ]

Indicate that files should be removed from the repository. The files will not actually be removed
until they are committed. Use cvs add to resurrect files that have been removed if you change
your mind later.

The standard meanings of the common client options -l and -R apply. Only one other option may
be used with the remove command, -f. When used, -f will delete the file from the sandbox first.

14.4.7.18. rtag
rtag [ -a ] [ -b ] [ -d ] [ -Ddate | -r rev ] [ -f ] [ -F ] [ -l | -R ] [ -n ]tag file...

Assign a tag to a particular revision of a set of files. If the file already uses the tag for a different
revision, cvs rtag will complain unless the -F option is used. This command does not refer to the
sandbox file revisions (use cvs tag for that), so it can be run outside of a sandbox, if desired.

The standard meanings of the common client options -D, -f, -l, -r, and -R apply. Additional
options are listed in Table 14-35.

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Table 14-35. rtag Options

Option Description

-a Search the Attic for removed files containing the tag.
-b Make it a branch tag.
-d Delete the tag.
-F Force. Move the tag from its current revision to the one specified.
-n Don't run any tag program from the modules file.

14.4.7.19. status
status [ -l | -R ] [ -v ] [file ... ]

Display the status of the files.
The standard meanings of the common client options -l and -R apply. The other option that can
be used with the status command, -v, may be used to include tag information.

14.4.7.20. tag
tag [ -b ] [ -c ] [ -d ] [ -Ddate | -r rev ] [ -f ] [ -F ] [ -l | R ]tag[ file ... ]

Assign a tag to the sandbox revisions of a set of files. You can use the status -v command to list
the existing tags for a file.

The tag must start with a letter and must consist entirely of letters, numbers, dashes (-) and
underscores (_). Therefore, while you might want to tag your hello project with 1.0 when you

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release Version 1.0, you'll need to tag it with something like hello-1_ 0 instead.

The standard meanings of the common client options -D, -f, -l, -r, and -R apply. Additional
options are listed in Table 14-36.

Table 14-36. tag Options

Option Description

-b Make a branch.
-c Check for changes. Make sure the files are not locally modified before tagging.
-d Delete the tag.
-F Force. Move the tag from its current revision to the one specified.

Since the -d option throws away information that might be important, it is recommended that
you use it only when absolutely necessary. It is usually better to create a different tag with a
similar name.

14.4.7.21. unedit
unedit [ -l | -R ] [file ... ]

Abandon file modifications and make the file read-only again. Watchers will be notified.
The standard meanings of the common client options -l and -R apply.

14.4.7.22. update
update [ -A ] [ -d ] [ -Ddate | -r rev ] [ -f ] [ -Ipattern ] [ -jrev1 [ -j rev2 ] ] [ -kkflag ] [ -l | -R ] [ -p ] [ -P ]

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[ -W spec ] [file ... ]

Update the sandbox, merging in any changes from the repository. For example:
cvs -n -q update -AdPcan be used to do a quick status check of the current sandbox versus the head of the trunk of
development.

The standard meanings of the common client options -D, -f, -k, -l, -r, and -R apply. Additional
options are listed in Table 14-37.

Table 14-37. update Options

Option Description

-A Reset sticky tags.
-d Create and update new directories.
-I pattern Provide filename patterns for files to ignore.
-j revision Merge in changes between two revisions. Mnemonic: join.
-p Check out files to standard output.
-P Prune empty directories.
-W spec Provide wrapper specification.

Using -D or -r results in sticky dates or tags, respectively, on the affected files (using -p along
with these prevents stickiness). Use -A to reset any sticky tags or dates.

If two -j specifications are made, the differences between them are computed and applied to the
current file. If only one is given, then the common ancestor of the sandbox revision and the
specified revision is used as a basis for computing differences to be merged.

For example, suppose a project has an experimental branch, and important changes to the file
foo. c were introduced between revisions 1.2.2.1 and 1.2.2.2. Once those changes have proven
stable, you want them reflected in the main line of development. From a sandbox with the head
revisions checked out, we run:

user@ localhost$ cvs update -j 1.2.2.1 -j 1.2.2.2 foo. cCVS finds the differences between the two revisions and applies those differences to the file in
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our sandbox.

The spec used with -W is in the same format as entries in the cvswrappers administrative file
(see Section 14.3.3.6, "The cvswrappers file").

The status codes listed in Table 14-38 are used to describe the action taken on each file
encountered in the repository and the sandbox.

Table 14-38. update Status Codes

Status Code Description

A Added. Server took no action because there was no repository file. Indicates that cvs add, but not cvs commit, has been run.
CConflict. Sandbox copy is modified (it has been edited since it was checked
out or last committed). There was a new revision in the repository, and there
were conflicts when CVS merged its changes into the sandbox version.

MModified. Sandbox copy is modified (it has been edited since it was checked
out or last committed). If there was a new revision in the repository, its
changes were successfully merged into the file (no conflicts).

P Patched. Same as U but indicates the server used a patch.

R Removed. Server took no action. Indicates that cvs remove, but not cvs commit, has been run.
U Updated. The file was brought up-to-date.
? File is present in sandbox but not in repository.

14.4.7.23. watch
watch { { on | off } | { add | remove } [ -aaction ] } [ -l | -R ]file ...

The watch command controls CVS's edit-tracking mechanism. By default, CVS operates in its
concurrent development mode, allowing any user to edit any file at any time. CVS includes this
watch mechanism to support developers who would rather be notified of edits made by others
proactively than discover them when doing an update.

The CVSROOT/ notify file determines how notifications are performed.

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Table 14-39 shows the watch sub-commands and their uses.

Table 14-39. watch Sub-commands

Sub-command Description

add Start watching files.
off Turn off watching.
on Turn on watching.
remove Stop watching files.

The standard meanings of the common client options -l and -R apply. The only other option that
can be used with the watch command is -a action. The -a option is used in conjunction with one
of the actions listed in Table 14-40.

Table 14-40. watch Actions

Action Description

all All of the following.
commit A user has committed changes.
edit A user ran cvs edit.
none Don't watch. Used by the edit command.

unedit A user ran cvs unedit, cvs release, or deleted the file and ran cvs update, re-creating it.

See also the descriptions of the edit, editors, unedit, and watchers commands.
14.4.7.24. watchers
watchers [ -l | -R ] [file ... ]

Display a list of users watching the specified files. This is determined by checking which users
have run the watch command on a particular file (or set of files). If the watch command has not
been used, no results will be displayed.

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The standard meanings of the common client options -l and -R apply.
See also watch.

14.3. CVS Administrator
Reference
14.5. The RCS Utility

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Linux in a Nutshell, 3rd
Edition

14.5. The RCS Utility
The Revision Control System (RCS) is designed to keep track of multiple file revisions,
thereby reducing the amount of storage space needed. With RCS you can automatically store
and retrieve revisions, merge or compare revisions, keep a complete history (or log) of
changes, and identify revisions using symbolic keywords. This chapter describes Version 5.7
but notes differences from earlier versions.

14.4. CVS User Reference 14.6. Overview of RCS
Commands

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Linux in a Nutshell, 3rd
Edition

14.6. Overview of RCS Commands
The three most important RCS commands are:
ci
Check in revisions (put a file under RCS control).
co

Check out revisions.
rcs

Set up or change attributes of RCS files.
Two additional commands provide information about RCS files:
ident
Extract keyword values from an RCS file.
rlog

Display a summary (log) about the revisions in an RCS file.
You can compare RCS files with these commands:
rcsdiff
Report differences between revisions.
rcsmerge

Incorporate changes from two RCS files into a third RCS file.
The following command helps with configuration management:

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rcsclean

Remove working files that have not been changed.

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Linux in a Nutshell, 3rd
Edition

14.7. Basic RCS Operations
Normally, you maintain RCS files in a subdirectory called RCS, so the first step in using RCS
should be:

mkdir RCSNext, you place an existing file (or files) under RCS control by running the check-in
command:

ci fileThis creates a file called file, v in directory RCS. file, v is called an RCS file, and it will store all
future revisions of file. When you run ci on a file for the first time, you are prompted to
describe the contents. ci then deposits file into the RCS file as revision 1.1.

To edit a new revision, check out a copy:
co -l fileThis causes RCS to extract a copy of file from the RCS file. You must lock the file with -l to
make it writable by you. This copy is called a working file. When you're done editing, you can
record the changes by checking the working file back in again:

ci fileThis time, you are prompted to enter a log of the changes made, and the file is deposited as
revision 1.2. Note that a checkin normally removes the working file. To retrieve a read-only
copy, do a checkout without a lock:

co fileThis is useful when you need to keep a copy on hand for compiling or searching. As a shortcut
to the previous ci/ co, you could type:

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ci -u file

This checks in the file but immediately checks out a read-only copy. To compare changes
between a working file and its latest revision, you can type:

rcsdiff fileAnother useful command is rlog, which shows a summary of log messages.
System administrators can use the rcs command to set up default behavior for RCS.

14.6. Overview of RCS
Commands
14.8. General RCS
Specifications

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Linux in a Nutshell, 3rd
Edition

14.8. General RCS Specifications
This section discusses:
l Keyword substitution
l Revision numbering
l Specifying the date
l Specifying states
l Standard options and environment variables

14.8.1. Keyword Substitution
RCS lets you place keyword variables in your working files. These variables are later expanded into
revision notes. You can then use the notes either as embedded comments in the input file or as text strings
that appear when the output is printed. To create revision notes via keyword substitution, follow this
procedure:

1. In your working file, type any of the keywords listed in the next section.
2. Check the file in.
3. Check the file out again. Upon checkout, the co command expands each keyword to include its
value. That is, co replaces instances of:

$keyword$ with:
$keyword: value$4. Subsequent checkin and checkout of a file will update any existing keyword values. Unless
otherwise noted later, existing values are replaced by new values.

NOTE
Note: Many RCS commands have a -k option that provides more flexibility during
keyword substitution.

14.8.1.1. Keywords
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$Author$
Username of person who checked in revision.
$Date$
Date and time of checkin.
$Header$
A title that includes the RCS file's full pathname, revision number, date, author, state, and (if
locked) the person who locked the file.

$Id$
Same as $Header$, but exclude the full pathname of the RCS file.
$Locker$
Username of person who locked the revision. If the file isn't locked, this value is empty.
$Log$
The message that was typed during checkin to describe the file, preceded by the RCS filename,
revision number, author, and date. Log messages accumulate rather than being overwritten.

$RCSfile$
The RCS filename, without its pathname.
$Revision$
The assigned revision number.
$Source$
The RCS filename, including its pathname.
$State$
The state assigned by the -s option of ci or rcs.

14.8.1.2. Example values
Let's assume that the file /projects/ new/ chapter3 has been checked in and out by a user named daniel.
Here's what keyword substitution would produce for each keyword, for the second revision of the file:

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$Author: daniel $

$Date: 2001/ 07/ 05 14: 25: 39 $ $Header: /projects/ new/ chapter3, v 1.2 2000/ 02/ 25 18: 21: 10 daniel \ Exp Locker: daniel $

$Id: chapter3, v 1.2 2001/ 07/ 05 14: 25: 39 daniel Exp $ $Locker: $ $Log: chapter3, v $ Revision 1.2 2001/ 07/ 05 14: 25: 39 daniel Added section on error handling

#Revision 1.1 2000/ 02/ 25 16: 49: 59 daniel #Initial revision #

$RCSfile: chapter3, v $ $Revision: 1.2 $ $Source: /projects/ new/ chapter3, v $ $State: Exp $

14.8.2. Revision Numbering
Unless told otherwise, RCS commands typically operate on the latest revision. Some commands have an -r
option that is used to specify a revision number. In addition, many options accept a revision number as
an optional argument. (In the command summary, this argument is shown as [R].) Revision numbers
consist of up to four fields, release, level, branch, and sequence, but most revisions consist of only the
release and level.

For example, you can check out revision 1.4 as follows:
co -l -r1.4 ch01When you check it in again, the new revision will be marked as 1.5. But suppose the edited copy needs to
be checked in as the next release. You would type:

ci -r2 ch01This creates revision 2.1. You can also create a branch from an earlier revision. The following command
creates revision 1.4.1.1:

ci -r1.4.1 ch01Numbers are not the only way to specify revisions, though. You can assign a text label as a revision
name, using the -n option of ci or rcs. You can also specify this name in any option that accepts a

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revision number for an argument. For example, you could check in each of your C programs, using the
same label regardless of the current revision number:

ci -u -nPrototype *. cIn addition, beginning with RCS Version 5.6, you can specify a $, which means the revision number is
extracted from the keywords of a working file. For example:

rcsdiff -r$ ch01compares ch01 to the revision that is checked in. You can also combine names and symbols. The
command:

rcs -nDraft:$ ch*assigns a name to the revision numbers associated with several chapter files.

14.8.3. Specifying the Date
Revisions are timestamped by time and date of checkin. Several keyword strings include the date in their
values. Dates can be supplied in options to ci, co, and rlog. RCS uses the following date format as its
default:

1999/ 10/ 16 02: 00: 00 (year/ month/ day time)The default time zone is Greenwich Mean Time (GMT), which is also referred to as Coordinated
Universal Time (UTC). Dates can be supplied in free format. This lets you specify many different styles.
Here are some of the more common ones, which show the same time as in the preceding example:

6: 00 pm lt (assuming today is Oct. 16, 1999) 2: 00 AM, Oct. 16, 1999 Sat Oct 16 18: 00: 00 1999 LT Sat Oct 16 18: 00: 00 PST 1999

The uppercase or lowercase lt indicates local time (here, Pacific Standard Time). The third line shows
ctime format (plus the LT); the fourth line is the date command format.

14.8.4. Specifying States
In some situations, particularly programming environments, you want to know the status of a set of
revisions. RCS files are marked by a text string that describes their state. The default state is Exp
(experimental). Other common choices include Stab (stable) or Rel (released). These words are user-defined
and have no special internal meaning. Several keyword strings include the state in their values. In
addition, states can be supplied in options to ci, co, rcs, and rlog.

14.8.5. Standard Options and Environment Variables
RCS defines the environment variable RCSINIT, which is used to set up default options for RCS

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commands. If you set RCSINIT to a space-separated list of options, they will be prepended to the
command-line options you supply to any RCS command. Three options are useful to include in
RCSINIT: -q, -V, and -x. They can be thought of as standard options because most RCS commands
accept them. Note that -V was new in RCS Version 5 and that -x was new in Version 5.6.

-q[ R]
Quiet mode; don't show diagnostic output. R specifies a file revision.
-V[ n]
Emulate version n of RCS; useful when trading files between systems that run different versions. n
can be 3, 4, or 5. If n is omitted, the command prints the version number of this version of RCS.

-xsuffixes
Specify an alternate list of suffixes for RCS files. Each suffix is separated by a /. On Unix systems,
RCS files normally end with the characters ,v. The -x option provides a workaround for systems
that don't allow a comma (,) character in filenames.

-z[ zone]
Specify the format of the date in keyword substitution. If empty, the default is to output the UTC
time with no zone indication. With an argument of LT, the local time zone will be used to output
an ISO 8601 format, with an indication of the separation from UTC. You may also specify a
numeric UTC offset. For example, -z+ 4: 30 would output a string such as: 1998-11-24
02: 30: 00+ 4: 30.

For example, when depositing a working file into an RCS file, the command:

ci -x, v/ ch01 (second suffix is blank)searches in order for the RCS filenames:
RCS/ ch01, v ch01, v RCS/ ch01

14.7. Basic RCS Operations 14.9. Alphabetical Summary
of RCS Commands

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Linux in a Nutshell, 3rd
Edition

14.9. Alphabetical Summary of RCS Commands
For details on the syntax of keywords, revision numbers, dates, states, and standard options, refer to the previous discussions.

ci ci [options] files
Check in revisions. ci stores the contents of the specified working files into their corresponding RCS files. Normally, ci deletes the working
file after storing it. If no RCS file exists, then the working file is an initial revision. In this case, the RCS file is created and you are prompted
to enter a description of the file. If an RCS file exists, ci increments the revision number and prompts you to enter a message that logs the
changes made. Starting with RCS Version 5.6, if a working file is checked in without changes, the file reverts to the previous revision. In
older RCS versions, you may end up having to check in a new revision that contains no changes.

The mutually exclusive options -u, -l, and -r are the most common. Use -u to keep a read-only copy of the working file (for example, so that
the file can be compiled or searched). Use -l to update a revision and then immediately check it out again with a lock. This allows you to save
intermediate changes but continue editing (for example, during a long editing session). Use -r to check in a file with a different release
number. ci accepts the standard options -q, -V, -x, and -z.

Options
-d[ date]
Check the file in with a timestamp of date or, if no date is specified, with the time of last modification.

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-f[ R]
Force a checkin even if there are no differences.
-I[ R]
Interactive mode; prompt user even when standard input is not a terminal (e. g., when ci is part of a command pipeline). -I was new in
RCS Version 5.

-i[ R]
Create (initialize) an RCS file and check it in. A warning is reported if the RCS file already exists.
-j[ R]
Check in a file without initializing. Will report an error if file does not already exist.
-k[ R]
Assign a revision number, creation date, state, and author from keyword values that were placed in the working file, instead of
computing the revision information from the local environment. -k is useful for software distribution: the preset keywords serve as a
timestamp shared by all distribution sites.

-l[ R]
Do a co -l after checking in. This leaves a locked copy of the next revision.
-mmsg
Use the msg string as the log message for all files checked in. When checking in multiple files, ci normally prompts whether to reuse
the log message of the previous file. -m bypasses this prompting.

-M[ R]
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Set the working file's modification time to that of the retrieved version. Use of -M can confuse make and should be used with care.
(This was new in RCS Version 5.6.)

-nname
Associate a text name with the new revision number.
-Nname
Same as -n, but override a previous name.
-r[ R]
Check the file in as revision R.
-r
By itself, reverts to default behavior when releasing a lock and removing the working file. This option overrides any -l or -u options
that have been initialized by shell aliases or scripts. This behavior for -r is specific to ci.

-sstate
Set the state of the checked-in revision.
-T
Set the RCS file's modification time to the time of the latest revision if the RCS file's time precedes the new revision.
-tfile
Replace RCS file description with contents of file. As of Version 5, this works only for initial checkin.
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-t-string
Replace RCS file description with string. As of Version 5, this works only for initial checkin.
-u[ R]
Do a co -u after checking in. This leaves a read-only copy.
-wuser
Set the author field to user in the checked-in revision.
Examples
Check in chapter files using the same log message:
ci -m'First round edits' chap*Check in edits to prog. c, leaving a read-only copy:
ci -u prog. cStart revision level 2; refer to revision 2.1 as "Prototype":
ci -r2 -nPrototype prog. c

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co co [options] files
Retrieve a previously checked-in revision, and place it in the corresponding working file (or print to standard output if -p is specified). If you
intend to edit the working file and check it in again, specify -l to lock the file. co accepts the standard options -q, -V, and -x.

Options
-ddate
Retrieve latest revision whose checkin timestamp is on or before date.
-f[ R]
Force the working file to be overwritten.
-I[ R]
Interactive mode; prompt user even when standard input is not a terminal. (New in RCS Version 5.)
-jR2: R3
This works like rcsmerge. R2 and R3 specify two revisions whose changes are merged into a third file: either the corresponding
working file or a third revision (any R specified by other co options).

-kc
Expand keyword symbols according to flag c. c can be:
b
Like o, but performs its operations in binary mode, generating the previous revision's keywords and values in binary.

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k
Expand symbols to keywords only (no values). This is useful for ignoring trivial differences during file comparison.
kv
Expand symbols to keyword and value (the default). Insert the locker's name only during a ci -l or co -l.
kvl
Like kv, but always insert the locker's name.
o
Expand symbols to keyword and value present in previous revision. This is useful for binary files that don't allow substring
changes.

v
Expand symbols to values only (no keywords). This prevents further keyword substitution and is not recommended.
-l[ R]
Same as -r, but also lock the retrieved revision.
-M[ R]
Set the working file's modification time to that of the retrieved version. Use of -M can confuse make and should be used with care.
(This was new in RCS Version 5.6.)

-p[ R]
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-r[ R]
Retrieve the latest revision or, if R is given, retrieve the latest revision that is equal to or lower than R.
-sstate
Retrieve the latest revision having the given state.
-T
Preserve the modification time of the RCS file even if a lock is added or removed.
-u[ R]
Same as -r, but also unlock the retrieved revision if you locked it previously.
-w[ user]
Retrieve the latest revision that was checked in either by the invoking user or by the specified user.
Examples
Sort the latest stored version of file:
co -p file | sortCheck out (and lock) all uppercase filenames for editing:
co -l [A-Z]*Note that filename expansion fails unless a working copy resides in the current directory. Therefore, this example works only if the files were
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previously checked in via ci -u. Finally, here are some different ways to extract the working files for a set of RCS files (in the current
directory):

co -r3 *, v Latest revisions of release 3co -r3 -wjim *, v Same, but only if checked in by jimco -d'May 5, 2 pm LT' *, v Latest revisions that were modified on or before the dateco -rPrototype *, v Latest revisions named Prototype

ident ident [option] [files]
Extract keyword/ value symbols from files. files can be text files, object files, or dumps.
Option
-q
Suppress warning message when no keyword patterns are found.
Examples
If file prog. c is compiled, and it contains this line of code:
char rcsID[] = "$ Author: ellie $";then the following output is produced:
% ident prog. c prog. oprog. c: $Author: ellie $ prog. o: $Author: ellie $

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Show keywords for all RCS files (suppress warnings):
co -p RCS/*, v | ident -q

rcs rcs [options] <files
An administrative command for setting up or changing the default attributes of RCS files. Among other things, rcs lets you set strict locking
(-L), delete revisions (-o), and override locks set by co (-l and -u). RCS files have an access list (created via -a); anyone whose username is
on the list can run rcs. The access list is often empty, meaning that rcs is available to everyone. In addition, you can always invoke rcs if you
own the file, if you're a privileged user, or if you run rcs with -i. rcs accepts the standard options -q, -V, -x, and -z.

Options
-ausers
Append the comma-separated list of users to the access list.
-Aotherfile
Append otherfile's access list to the access list of files.
-b[ R]
Set the default branch to R or, if R is omitted, to the highest branch on the trunk.
-c`s'
The comment character for $Log keywords is set to string s. By default, co expands embedded $Log keywords into comments
preceded by #. You could, for example, set s to .\" for troff files or set s to * for C programs. (You would need to manually insert an
enclosing /* and */ before and after $Log.)

-e[ users]
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Erase everyone (or only the specified users) from the access list.
-i
Create (initialize) an RCS file, but don't deposit a revision.
-I
Interactive mode; prompt user even when standard input is not a terminal. (New in RCS Version 5.)
-kc
Use c as the default style for keyword substitution. (See co for values of c.) -kkv restores the default substitution style; all other styles
create incompatibilities with RCS Version 4 or earlier.

-l[ R
Lock revision R or the latest revision. -l "retroactively locks" a file and is useful if you checked out a file incorrectly by typing co
instead of co -l.

-L
Turn on strict locking (the default). This means that everyone, including the owner of the RCS file, must use co -l to edit files. Strict
locking is recommended when files are to be shared. (See -U.)

-mR: msg
Use the msg string to replace the log message of revision R. (This was new in RCS Version 5.6.)
-M
Disable email notification when breaking a lock on a file with rcs -u. This should only be used when there is another means to warn
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users that their files have been unlocked.
-nflags
Add or delete an association between a revision and a name. flags can be:
name: R
Associate name with revision R.
name:
Associate name with latest revision.
name
Remove association of name.
-Nflags
Same as -n, but overwrite existing names.
-oR_ list
Delete (outdate) revisions listed in R_ list. R_ list can be specified as R1, R1-R2, R1-, or -R2. When a branch is given, -o deletes only
the latest revision on it. RCS Version 5.6 changed the range separator character to :, although -is still valid.

-sstate[: R]
Set the state of revision R (or the latest revision) to the word state.
-t[ file]
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Replace RCS file description with contents of file or, if no file is given, with standard output.
-t-string
Replace RCS file description with string. Preserves the time of modification on an RCS file unless a revision is removed.
-T
Preserve the modification time of the RCS file.
-u[ R]
The complement of -l: unlock a revision that was previously checked out via co -l. If someone else did the checkout, you are
prompted to state the reason for breaking the lock. This message is mailed to the original locker.

-U
Turn on nonstrict locking. Everyone except the file owner must use co -l to edit files. (See -L.)
-V
Print the RCS version number.
-zzone
Set the default time zone for timestamp options performed by the ci and co commands.
Examples
Associate the label To_ customer with the latest revision of all RCS files:
rcs -nTo_ customer: RCS/*file:/// E|/ O'Reilly/ O'Reilly% 20-% 20Linux% 20in% 20a% 20Nutshell,% 203rd% 20Edition/ Pages/ ch14_ 09. htm (12 of 19) [15/ 05/ 2002 18: 12: 57] 850
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Add three users to the access list of file beatle_ deals:
rcs -ageorge, paul, ringo beatle_ dealsDelete revisions 1.2 through 1.5:
rcs -o1.2-1.5 docReplace an RCS file description with the contents of a variable:
echo "$ description" | rcs -t file

rcsclean rcsclean [options] [files]
Compare checked-out files against the corresponding latest revision or revision R (as given by the options). If no differences are found, the
working file is removed. (Use rcsdiff to find differences.) rcsclean is useful in makefiles. For example, you could specify a "clean-up" target
to update your directories. rcsclean is also useful prior to running rcsfreeze. rcsclean accepts the standard options -q, -V, -x, and -z.

Options
-kc
When comparing revisions, expand keywords using style c. (See co for values of c.)
-n[ R]
Show what would happen, but don't actually execute.
-r[ R]
Compare against revision R. R can be supplied as arguments to other options, so -r is redundant.
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-T
Preserve the modification time of the RCS file even if a lock is added or removed.
-u[ R]
Unlock the revision if it's the same as the working file.
Examples
Remove unchanged copies of program and header files:
rcsclean *. c *. h

rcsdiff rcsdiff [options] [diff_ options] files
Compare revisions via diff. Specify revisions using -r as follows:
Number of Revisions Specified: Comparison Made:None Working file against latest revision One Working file against specified revision Two One revision against the other

rcsdiff accepts the standard options -q, -T, -V, -x, and -z, as well as diff_ options, which can be any valid diff option. rcsdiff exits with a
status of 0 (no differences), 1 (some differences), or 2 (unknown problem).

Options
-kc
When comparing revisions, expand keywords using style c. (See co for values of c.)
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-rR1
Use revision R1 in the comparison.
-rR2
Use revision R2 in the comparison. (-rR1 must also be specified.)

rcsmerge rcsmerge [options] file
Perform a three-way merge of file revisions, taking two differing versions and incorporating the changes into the working file. You must
provide either one or two revisions to merge (typically with -r). Overlaps are handled the same as with merge, by placing warnings in the
resulting file. rcsmerge accepts the standard options -q, -V, -x, and -z. rcsmerge exits with a status of 0 (no overlaps), 1 (some overlaps), or
2 (unknown problem).

Options
-kc
When comparing revisions, expand keywords using style c. (See co for values of c.)
-p[ R]
Send merged version to standard output instead of overwriting file.
-r[ R]
Merge revision R or, if no R is given, merge the latest revision.
Examples

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Suppose you need to add updates to an old revision (1.3) of prog. c, but the current file is already at revision 1.6. To incorporate the changes:
co -l prog. c(edit latest revision by adding revision 1.3 updates, then:)rcsmerge -p -r1.3 -r1.6 prog. c > prog. updated. c

Undo changes between revisions 3.5 and 3.2, and overwrite the working file:
rcsmerge -r3.5 -r3.2 chap08

rlog rlog [options] files
Display identification information for RCS files, including the log message associated with each revision, the number of lines added or
removed, date of last checkin, and so on. With no options, rlog displays all information. Use options to display specific items. rlog accepts
the standard options -T, -V, -x, and -z.

Options
-b
Prune the display; print only about the default branch.
-ddates
Display information for revisions whose checkin timestamp falls in the range of dates (a list separated by semicolons). Be sure to use
quotes. Each date can be specified as:

date1< date2
Select revisions between date1 and date2, inclusive.
date1 <
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Select revisions made on or after date1.
date1
Select revisions made on or before date1.
-h
Display the beginning of the normal rlog listing.
-l[ users]
Display information only about locked revisions or, if lockers is specified, only revisions locked by the list of users.
-L
Skip files that aren't locked.
-N
Don't display symbolic names.
-r[ list]
Display information for revisions in the comma-separated list of revision numbers. If no list is given, the latest revision is used. Items
can be specified as:

R1
Select revision R1. If R1 is a branch, select all revisions on it.
R1.
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If R1 is a branch, select its latest revision.
R1-R2
Select revisions R1 through R2.
-R1
Select revisions from beginning of branch through R1.
R1-Select
revisions from R1 through end of branch.
RCS Version 5.6 changed the range separator character to :, although -is still valid.
-R
Display only the name of the RCS file.
-sstates
Display information for revisions whose state matches one from the comma-separated list of states.
-t
Same as -h, but also display the file's description.
-w[ users]
Display information for revisions checked in by anyone in the comma-separated list of users. If no users are supplied, assume the
name of the invoking user.
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Examples
Display a file's revision history:
rlog RCS/*, v | moreDisplay names of RCS files that are locked by user daniel:
rlog -R -L -ldaniel RCS/*Display the "title" portion (no revision history) of a working file:
rlog -t calc. c

14.8. General RCS
Specifications
15. GNOME

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Chapter 15. GNOME
Contents:
Desktop Overview
The Panel
The Main Menu
The GNOME Control Center

GNOME stands for the GNU Network Object Model Environment. It is a user-friendly,
graphically driven environment that controls the look and feel of your desktop and provides a
consistent method of interaction and cooperation between applications. GNOME is one of two
popular desktop environments used with Linux. It is standard with Red Hat, Debian, and other
popular distributions. The other popular Linux environment is called KDE, which is discussed
in Chapter 16, "KDE".

GNOME is not a window manager. As a graphical environment, it provides users with a
highly customizable user interface and consistent functionality of common GUI features such
as menus, toolbars, and buttons. As a user environment, GNOME utilizes a growing set of
native applications to create a productive computing system.

One of GNOME's most attractive features is its CORBA-based architecture, which allows
interaction among applications through the sharing and embedding of component objects.
CORBA stands for Common Object Request Broker Architecture. It specifies methods that
software objects use to interact with each other through an ORB (object request broker). The
ORB package currently used by GNOME is the ORBit package
(http:// www. labs. redhat. com/ orbit). ORBit allows similar functionality to Window's COM and

OLE. For example, a spreadsheet created by gnumeric (a GNOME spreadsheet program) can
be placed as an object into an AbiWord document.

GNOME does rely on a window manager to handle the particulars of the X Window System
environment. The window manager controls the placement, movement, and graphical style of
the windows on your screen. You can use GNOME with many different window managers,
but they must be compliant with GNOME in order to utilize features such as drag-and-drop.

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Sawfish and Enlightenment are commonly used window managers and are fully compliant
with the GNOME environment. Other window managers that can be used are IceWM,
WindowMaker, and AfterStep.

15.1. Desktop Overview
Figure 15-1 shows the default GNOME desktop. The left side of the screen contains icons that
are shortcuts to open applications. The top icon is a symbolic link to the user's home folder,
and when double-clicked, opens the GNOME file manager displaying that folder. The other
icons include shortcuts to the floppy drive and CD-ROM and links to web pages. Desktop
icons can be used to launch any program on your system, invoke the appropriate application
for a data file or view a directory or URL.

Figure 15-1. The GNOME desktop
The bar across the bottom of the screen is the GNOME panel. It is your primary means of
finding and opening applications and managing your desktop. The panel contains launcher
buttons for the main menu, help and configuration tools, and the Netscape browser. You can
add buttons to the control panel to launch any application on your system.

The panel also runs two special programs (called applets) that help you get around your
desktop. The Desk Guide applet displays your desktop workspace. Many window managers
allow you to divide your workspace into a number of different screens (called virtual desktops
or viewports). Desk Guide provides a small display of the available desktops and outlines of
the windows they contain. Clicking on an area of the display will switch your desktop view.

The Tasklist applet lets you keep track of open windows. It displays a button on the panel for
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each window you have open. Clicking on a button in the tasklist will bring focus to its
window or reopen it if it was minimized.

GNOME allows you an enormous number of configuration options for your desktop
environment. You can right-click on just about anything and get a pop-up menu (called a
context menu) containing specific actions for that item and a way to configure its properties.
General configuration settings are contained in the GNOME Control Center. You can access
this tool in the following ways: click the toolbox button on the panel to open the Control
Center window, or from the main menu, select Settings, then GNOME Control Center
(individual configuration applications also are accessible from this menu).

15.1.1. Adding Desktop Icons
Desktop icons offer you convenient double-click access to your most important files,
applications, and links. The items displayed on your desktop exist as files in the .gnome-desktop
directory of your home directory. Anything you add to that directory will appear on
the desktop.

The desktop context menu contains a New submenu that allows you to add different types of
items to your desktop.

To add an icon that launches an application, select New Launcher. This opens the Desktop
Entry Properties dialog box shown in Figure 15-2. Provide the name of the launcher (this will

be the text displayed underneath the icon), a comment (this will be the tooltip that appears
when the pointer is over the icon), and the command used to run the application. After you
click OK, the new launcher icon appears on your desktop.

Figure 15-2. Desktop entry properties
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To add a desktop icon that opens a directory, select New Directory from the desktop
context menu. Provide the name of a directory in the dialog box. If you specify a full
pathname, the desktop icon will be created as a symbolic link. If it is not a full pathname, the
new directory will be created in ~/. gnome-desktop.

To add a URL link to the desktop, select New URL Link from the desktop context menu.
This will open a dialog box that asks you for the URL you wish to open and a caption to use
as the icon's text label. Click OK, and the icon appears on your desktop. You also can click
and drag any link displayed in the Netscape browser to the desktop to create a link.

A convenient use of desktop icons is to have shortcuts to frequently used files or folders.
Adding shortcuts is easiest from the file manager (gmc). If you click on an item in the file
manager and drag it to the desktop, you will create a launcher icon for it. This action actually
moves the item to the ~/. gnome-desktop folder. If you press the Ctrl key while selecting and
dragging the item, you will only copy the item to the desktop. If you middle-click or press Alt
while selecting and dragging an item, a small pop-up window will ask you if you want to
move, copy, or link the file. Selecting Link Here will create a symbolic link on the desktop
that points to the original location of the item. For most files and folders, you may find this a
best option.

14.9. Alphabetical Summary
of RCS Commands
15.2. The Panel

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15.2. The Panel
The GNOME panel can contain several different types of objects. The most obvious are the
buttons for the menu and application launchers. You also can use a button to open a drawer,
which is like a subpanel containing additional launchers. There are a few special types of
buttons used for logging out of the session and locking the screen. Finally, small programs
called applets can be run on the panel. The Desk Guide and the clock are examples of panel
applets.

Settings for the panel are found in the Panel menu on the main menu or by right-clicking on
the panel. This menu offers options to add new launchers or applets to the panel; adjust the
style, size, and display of the panel; or create new panels on the desktop.

15.2.1. Additional Panels
You can create more than one panel on your desktop. This is useful if you have different sets
of applications used for specific but common tasks. For example, if you do a lot of work on
graphics, you can dedicate a panel to launch your favorite graphics tools. To create a new
panel, right-click on the default panel and select Add New Panel. Or from the main menu,
select Panel Add New Panel. There are five different types of panels available from the
submenu:

edge panel
The style of the default panel. It stretches across one entire edge of the screen. Arrow
buttons on each end of the panel are used to collapse the panel to the side of a screen.
Clicking on the remaining visible arrow button of a collapsed panel will cause the
panel to appear again in full.

aligned panel
A similar panel that is effectively anchored to one corner of the screen and extends just
enough to fit the buttons and applets it contains. An aligned panel can be hidden by
clicking the arrow button that is at the edge of the screen. The arrow button farthest
from the edge will anchor an aligned panel on the opposite side of the screen.

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sliding panel
Like an aligned panel except that it can be placed anywhere along the edge of the
screen. It is not anchored to a corner.

floating panel
As you'd suspect, a panel that can be placed anywhere on the screen.
menu panel
A special type of panel that stretches along the top of the screen. It is a thin bar that
contains drop-down menus for the Programs, Favorites, Settings, and Desktop menus
found in the main menu.

All of the panels except the menu panel can be moved by middle-clicking (or clicking the left
and right buttons simultaneously) and dragging the panel to another part of the screen where it
can be placed.

Each panel can be configured individually from the Panel menu in its context (right-click)
menu. Right-click and select Panel Properties. Here you can choose from several different
menu options. The Type submenu changes the panel's type (although a menu panel cannot be
changed to another type of panel). The Hiding Policy submenu has settings for Explicit Hide,
where you click one of the arrow buttons to collapse the panel to the side of the screen; or
Auto Hide, where the panel automatically reduces when not in use. The Hide Buttons
submenu allows you to show or hide the arrow and hide buttons of a panel. The Size submenu
sets the size of the panel from tiny to huge. The Background Type submenu lets you set the
background of a panel to either a color or a pixmap image.

To access all of the panel's properties in one dialog, select All Properties from this menu.
Global property settings are found in the GNOME Control Center. They are described later in
this chapter.

15.2.2. Adding an Application Launcher to the Panel
One of the conveniences of the panel is creating launcher icons that allow you one-click
access to frequently used applications. To add an application, right-click the panel and select
Add New Launcher. You also can right-click on an application in the main menu and choose
Add This Launcher to Panel.

In each case, the Create Launcher Applet dialog will appear. Provide a name for the
application, a comment to be used as a tooltip, and the command used to open the application.
Click on the icon button to select the image to be used for the button on the panel. If the

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application is to be run in a Terminal, click the Run in Terminal button.

The drag-and-drop functionality of GNOME allows you to place applications on the panel in a
number of ways. For example, you can click on an application file in the file manager and
drag it to the panel. This will open the Add New Launcher dialog and create a new launcher
button on the panel. You also can drag a desktop icon to the panel.

You can configure a launcher's properties by right-clicking it and selecting Properties. This
opens the Launcher Properties window, where you can change the name, comment, command,
application type, and icon used for the launcher.

Launcher buttons can be placed in any position and order you want on the panel. To move a
launcher button, right-click it and select Move. The mouse pointer will change, allowing you
to drag the button to another position. Click to set the new position of the button.

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15.3. The Main Menu
By default, the GNOME panel contains one menu --the main menu. It is displayed using the
first button on the right with the GNOME foot icon on it (sometimes it is called the foot
menu). The default main menu offers a number of items and submenus divided into sections:

l The System menu contains items for installed GNOME applications and utilities,
separated into additional submenus by categories, such as Graphics, Utilities, Internet,
and so on. Two items are included at the bottom of the System menu: Help opens the
GNOME help browser, and Run Command opens the single command-line prompt
window. The System menu can be changed only by a user with root access, and this
action will change it for all users.

l The User menu is empty by default. Individual users can add their own items to the
User menu section.

l If other packages, like KDE or AnotherLevel, are installed on your system, their
default menus also may be included in the main menu.

l The Panel menu contains actions and configuration shortcuts for the panel. The items
in this menu also are found in the pop-up menu accessed by right-clicking on the panel.

l The four items at the bottom of the menu allow you to lock the screen (requiring the
user's password to reenter the desktop), view version information for the panel, and log
out.

You will notice that the top entry for each menu section and each submenu is not an
actionable item. It is the titlebar for the menu. Right-clicking a titlebar opens a pop-up menu
containing a couple of options:

Add this as drawer to panel
Takes the current submenu and converts it to a drawer on the panel.
Add this as menu to panel
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Copies the menu to a new menu launcher on the panel. Keep in mind that the submenu
from the main menu and the menu on the panel are the same. You can edit the
submenu in the menu editor, and the changes will occur in the Panel menu.

Add this to personal menu
Copies the menu to the User menu.
The default configuration of the main menu makes it a bit difficult to customize. Since the
System menus are set and cannot be altered (unless you are root), you can initially configure
only the User menu section.

The best way to make a fully customizable main menu (other than being root all the time) is
to copy the desired parts of the System menu to your User menu. Once you have done this,
you can edit the User menu in the menu editor to your liking.

15.3.1. Menu Display Properties
You can choose which menus are displayed by using the menu properties. Right-click the
menu button and choose Properties to open this dialog. The Menu Properties window contains
display settings for the System menu, User menu, and any other default menus you have
installed. You can choose to display each menu as either fully listed, in a submenu, or not
displayed at all.

15.3.2. Editing the Menu
The Menu Editor, shown in Figure 15-3, lets you add and remove items from your menu and
move them around. To open the menu editor, select Settings, then Menu Editor from the main
menu.

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Figure 15-3. The Menu Editor
The menu editor is divided into two sections: the left window displays the hierarchy of the
User and System menus and the items they contain. You can reorder menu items or move
them to other submenus by clicking and dragging them in the left window. The right window
shows the properties of an item selected in the left window.

The buttons on the toolbar provide you with the following actions on a selected menu item:
add a new submenu, add a new item, delete the selection, move it up or down, and sort a
submenu.

To add a new submenu, select the menu in which you want to place it in the menu tree and
click the New Submenu button. Provide the name of the submenu in the right window and
click OK.

To add a new item to the menu, select its location in the menu tree and click the New Item
button. The right window displays the properties settings for the item. Type in the name for
the item, a comment for the tooltip, the command to launch the item, and its application type.
Click OK to add the item to the menu.

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15.2. The Panel 15.4. The GNOME Control
Center

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15.4. The GNOME Control Center
The GNOME Control Center (Figure 15-4) is where most customization and configuration of
your desktop environment takes place. Open the Control Center using the toolbox button on
the panel, or from Utilities on the main menu. The Control Center contains a number of
configuration applications, called capplets, that allow you to change various GNOME
settings. The capplets are listed in the left pane of the Control Center window, and clicking on
a name opens the capplet in the right pane.

Figure 15-4. GNOME Control Center
15.4.1. Desktop Settings
These sections provide settings for the overall look of your desktop by letting you choose the
background, screensaver, theme, and window manager.

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15.4.1.1. Background
Here's where you set your desktop background. You can choose to use an image for wallpaper
or colors. In the wallpaper section, click the Browse button to select an image file from the
filesystem. You can choose to have the image tiled on the background, centered, or scaled. In
the color section, select to use either a solid, single color, or a horizontal or vertical gradient
of two colors. Click the boxes for primary color and secondary color to pick the color.

This capplet sets the background via GNOME. Window managers also can set the background
and can sometimes conflict with the GNOME setting. To ensure that GNOME sets the
background, check the box labeled Use GNOME to Set Background at the bottom of the
window.

15.4.1.2. Screensaver
Contains settings for the screensaver. You can choose from a list of available screensavers
(including a random setting). Input the number of minutes of inactivity before the screensaver
starts and whether you, the user, will be required to give your password before going back to
the desktop. Power management settings are available here if your system is configured for
them.

15.4.1.3. Theme selector
Themes provide a consistent overall style to the many widgets and components used by
GNOME. A number of basic themes are included with the gtk-engines package, and you can
download and install additional themes from http:// gtk. themes. org.

Anythemes that are installed on your system are listed in the Theme Selector. You can select
one and preview it in the lower section of the window. If you click Auto Preview, a theme
will preview automatically when you click on it. Otherwise, click the Preview button to see
how it looks.

If you have downloaded a theme and wish to install it, click the Install New Theme button.
Provide the name and location of the .tar. gz or .tgz file and click OK. The new theme will be
installed in the /usr/ share/ themes directory and be available for you to use on your desktop.

15.4.1.4. Window manager
This section allows you to select the window manager that GNOME will use and configure its
properties if it has a configuration tool. By default, GNOME runs with the Enlightenment
window manager. Other window managers may be used, but make sure that they are
compliant with the GNOME architecture so as not to create problems for your applications.

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The listing shows installed window managers that you can use. You can add a new window
manager to the list by clicking the Add button. Type the window manager's name in the dialog
box. If it has its own configuration tool, supply the tool name and location, too. A button
underneath the list will be enabled stating Run the Configuration Tool for wm-name. Clicking
this button will open the configuration application for that window manager.

15.4.2. Panel
Panels can be configured individually or globally. For individual configuration, right-click on
the panel and select This Panel's Properties.

Most of the panel settings are made in the global panel configuration tool shown in Figure 15-
5. To open this tool, select Global Preferences from the Panel menu.

Figure 15-5. Panel configuration settings
The global panel configuration section of the Control Center opens. It contains the following
sections:

15.4.2.1. Animation
This tab controls the animated movements of the panel, such as when the panel is hidden or a
drawer is opened. At the top of the tab is a radio button to enable or disable animation
entirely. The rest of the settings are done with slider bars. The first two sliders to determine
how fast or slow the panel will collapse when it minimizes under autohide and when you
explicitly hide the panel with the arrow buttons. The next slider sets the speed of the opening
and closing of drawers. For autohide panels, there are additional sliders for the amount of time

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before the panel minimizes and the size (in pixels) of the hidden panel.

15.4.2.2. Buttons
This tab controls the look of the various types of buttons on a panel (See Figure 15-5). Select
which type of button you want to configure from the drop-down box.

Tiles provide a square background for a panel icon instead of the icon being displayed directly
on the panel background. If you enable tiles (using the radio button at the top), you can select
an image to use for the background of all buttons on the menu. Tiles also are used to create
3D-style buttons on the panel. You can choose the images for the up position and the down
position (i. e., on a mouse-down). To select the image files, click the tile images, and the
image file selection dialog opens for you to choose from.

Two slider controls allow you to set the number of pixels used for the border width around
tiles and the depth of the icon when pressed.

The following additional settings are available:
Make buttons flush with panel edge
This setting causes buttons to be placed at the edges of the panel. There is no visible
space between the button and the desktop background, although there is still spacing
between panel buttons.

Show button tiles only when cursor is over them
This setting causes tiles to be unseen until the mouse pointer is over the button.
Prelight buttons on mouse-over
This setting causes buttons to "light up" when the pointer is over them.

15.4.2.3. Panel objects
This tab allows you to select among three methods of icon placement: Switched Movement
makes icons switch places with the icon you are moving. This is the default behavior. Free
Movement locks the current icons in place as you move another icon. Icons can be moved
only to empty areas of the panel when this method is selected. Push Movement causes moving
icons to push the others around but not move over them.

The Padding slider sets the amount of space (in pixels) separating objects on the panel.

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15.4.2.4. Menu

This tab contains the global menu settings.
The first radio button enables large icons to be used for each menu item, indicating whether it
is a folder, file, or application.

The second radio button, Show ... Buttons, toggles the cascading display of submenus off and
on. If this button is selected, buttons containing ... are displayed for each menu item that
contains a submenu. The submenu is displayed only when you press the ... button. Automatic
display of cascading menus is used if this button is not selected.

The Show Pop-Up Menus Outside of Panels button controls the relative placement of pop-up
menus to the panel. If this is enabled, pop-up menus are displayed on the desktop so that they
don't overlap the panel. The Keep Menus in Memory button allows you to cache recently
opened menus in memory, providing faster response from your desktop environment.

The remainder of this tab configures which sections of the menu you want to display. You
have a choice of placing the sections directly on the main menu, placing them in a submenu,
or not showing the sections.

15.4.2.5. Miscellaneous
The Miscellaneous tab provides a number of panel configuration settings:
Tooltips enabled
Enables tooltips to be displayed for launcher icons.
Close drawer if launcher inside it is pressed
Causes a drawer to close after one of its items is selected. Otherwise, it will remain
open until you click on its closing arrow.

Raise panels on mouse-over
Causes the panel to come to the foreground on mouse-over if it is covered by another
window.

Keep panel below windows
Allows GNOME-compliant applications to display over the panel (normally they
would not cover the panel).

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Confirm the removal of panels with a dialog

A pop-up window will ask you if you really want to remove a panel.

15.4.3. Document Handlers
This section configures the default programs used to run specific files based on their content
type or URL.

15.4.3.1. Default editor
This section sets the text editor to be used by default when you open an editable file or choose
the Edit menu command on a file within the file manager. A drop-down list of available
editors is displayed. Click the Run in Terminal Window button if your chosen editor must be
run in a terminal.

15.4.3.2. Mime types
This section allows you to set or edit mime types. Click the Add button to add a new type. A
dialog will open asking for the category/ type listing for the mime type and the extensions to
associate with it. Optionally, you can supply up to two regular expressions to identify the
mime type. To edit a mime type, select it in the listing and click the Edit button. You will see
a dialog box in which you can choose an icon to be used for the file type, add or remove file
extensions, and supply commands that will open, view, and edit this type of file. To delete a
type, select it from the list and click the Delete button.

15.4.3.3. URL handlers
This page allows you to adjust the settings for special URL launchers used by the GNOME
help system. The defaults for protocols such as HTTP, FTP, and Mail are already set and
likely handled by your default web browser (for example, Netscape). The special URLs are
ghelp, info, and man, corresponding to GNOME help files, command info files, and man files.
The defaults use the help browser for these types of files. It is best to leave these settings as
they are.

15.4.4. Multimedia
This section adjusts the settings for system sounds.

15.4.4.1. Sound
This page sets up a sound scheme for various actions. You can enable or disable all sounds on

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the General tab. The Sound Events tab displays a listing of available events and the sound
files used for them. Select an event from the listing and click Play to hear its assigned sound.
Use the textbox to input the name of the sound file to assign to an action, or use the Browse
button to locate a sound file on the filesystem.

15.4.5. Peripherals
This section provides configuration settings for the keyboard and mouse.

15.4.5.1. Keyboard
Contains settings for keyboard autorepeat and sounds. You can set the repeat rate of a pressed
key and the delay before it starts. You also can enable keyboard clicks and their volume.
Settings can be previewed by typing in the Test Settings textbox.

Three sliders adjust the volume, pitch, and duration of the keyboard bell. Click the Test button
to hear the the bell's new settings.

15.4.5.2. Mouse
Lets you set the mouse to be configured for either a righthanded user or a lefthanded user.
You also can set the acceleration and threshold (sensitivity) of the mouse.

15.4.6. Session
This section contains settings for programs loaded at the start of each session.

15.4.6.1. Startup hint
The Startup Hint is a program that displays a message every time you log in. Hints can
provide a useful tip for a GNOME function that the user might not yet know about. You also
can use this program to display a fortune or a message of the day.

15.4.6.2. Startup programs
Since GNOME is session-aware, applications that are open when you log off are remembered
and reopened the next time you log in. Not all applications are compliant with the GNOME
session state, however. If you would like to set up programs to automatically start at login,
you can configure them here. You can add, edit, or delete startup programs and view the
currently running programs.

At the top of the window, there is an option button to show the splash screen on login. Two
additional buttons give you the option either to be prompted to save session changes on logout

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or to automatically save the changes.

15.4.7. User Interface
This section sets various properties for application window components such as menus,
toolbars, status bars, and dialog boxes.

15.4.7.1. Applications
The settings available in the applications section control the behavior of menus, toolbars, and
status bars for GNOME applications.

Menu bars in GNOME applications can be detached from windows and placed anywhere on
the desktop. This is the default behavior.

A detachable menu will have a small bar placed on its left edge. Click on this bar and drag to
move the menu bar to another part of the desktop. To redock the menu bar, drag it back to the
titlebar of its application window, and it will reattach.

For unmovable menu bars, unselect the the radio button labeled Can Detach and Move
Menus.

The same detachable functionality is applied to submenus by default. To disable this behavior,
unselect the radio button labeled Submenus Can Be Torn Off.

Three settings allow you to display menus, toolbars, and buttons on toolbars with a relieved
border. The relieved border gives a three-dimensional visual appearance to the components;
otherwise, they appear very flat.

Two options are available for status bars displayed at the bottom of windows. If a progress
meter is used in a status bar, you can configure it to always appear on the right side of the
statusbar. If this setting is disabled, the application will determine the progress meter
placement.

Some statusbars may have user functionality defined by the application. You can enable
statusbar interactivity with the supplied setting.

15.4.7.2. Dialogs
This page is divided into sections for the look of dialog windows and the positioning of dialog
windows.

The Dialog Layout section allows you to configure the position of dialog buttons with the

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following options: Default, Spread Buttons Out, Put Buttons on Edges, Left-justify Buttons,
and Right-justify Buttons. You also can enable or disable icons for dialog buttons and choose
to use a window's statusbar instead of a dialog, when possible.

The Dialog Behavior section allows you to set the position of dialog windows with the
following options: Let Window Manager Decide, Center of the Screen, and At the Mouse
Pointer. You also can configure dialog hints and enable the automatic placement of a dialog
over the application window from which it was launched.

15.4.7.3. MDI
MDI (Multiple Document Interface) describes the way multiple open documents are displayed
in an application window. There are three styles available: Modal, Toplevel, and Notebook.
Modal is the default setting. If you choose the Notebook style, you can set the document tab
position to either left, right, top, or bottom.

15.4.8. Sawfish Window Manager Configuration
The Sawfish window manager is the default window manager used by the Helix GNOME
Desktop used in the figures in this chapter. Sawfish is GNOME-compliant, working well not
to overlap the GNOME desktop settings. The Helix version of the GNOME Control Center
integrates the Sawfish configuration settings instead of using a separate configuration tool.
The Sawfish section of the Control Center is shown in Figure 15-6.

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Figure 15-6. Sawfish configuration settings

The following sections describe the Sawfish configuration settings contained in the Helix
GNOME Control Center.

15.4.8.1. Appearance
This section sets the default appearance of windows, including the style of the window frame,
fonts, and movement style.

The drop-down box contains a list of frame styles. The frame style determines how the
titlebars of windows are displayed by customizing the buttons and background of the title.

Some pop-up windows are configured to be displayed without the window titlebar. To force
the display of the title bar for all windows, click the button labeled Decorate Transient
Windows Similarly to Top-level Windows.

The default window animation mode determines the display of windows when they are being
minimized. You can choose from solid or wireframe modes or None for no animation.

The font button allows you to select the default desktop font. The default font is set by the
GNOME desktop theme and Sawfish is aware of the setting so that they match.

15.4.8.2. Focus behavior
This section contains settings that determine how windows receive the input focus.
The selection box at the top determines how the mouse pointer sets focus. The default is to
focus when the mouse clicks on the window. The other choices are to focus only when the
pointer is in the window (" enter-exit") and focus stays with the last window entered (" enter-only").

Three checkboxes are used to enable the following focus policies: focus each window when
first displayed, transient windows inherit focus from their parent, and raise windows when
they are focused. You can set the delay (in milliseconds) between focus and the time the
window is raised (brought to the foreground).

The advanced section contains the following additional settings:
l Give focus to windows even when they haven't asked for it.

l Offset from left window edge when warping.
l Offset from top window edge when warping.
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l Does click-to-focus mode pass the click through to the window?
The Shade Hover section contains settings for the behavior of shaded windows. A shaded
window is effectively rolled up, like a window shade, into its titlebar, usually by double-clicking
on the titlebar. If you check the button to enable shade hover, a shaded window will
temporarily unshade when the mouse pointer is placed on its titlebar. The next box allows you
to select the delay (in milliseconds) before unshading occurs. The final setting in this section
enables windows to be raised automatically when they are unshaded.

15.4.8.3. Minimizing and maximizing
This window contains settings for minimizing and maximizing windows. The settings for
minimizing windows are as follows:

Windows are uniconified onto the current workspace
Minimized windows are opened on the current desktop workspace when they are
clicked in the tasklist. You will usually have only one workspace in GNOME, which is
divided into a grid of separate screens called viewports.

Windows are raised after being uniconified
Minimized windows are opened in the foreground when they are clicked in the tasklist.
Windows are focused after being uniconified
Minimized windows receive keyboard focus when they are clicked in the tasklist.
Iconifying a window that's a member of a group removes the whole group
If you minimize a window that is part of a group (e. g., an application may spawn
several child windows from the main window), the whole group of windows will be
minimized.

Uniconifying a window that's a member of a group restarts the whole group
In conjunction with the previous setting, a minimized window group will reopen if one
of its members is raised.

Windows are uniconified to the current viewport
Minimized windows will reopen in the current screen, regardless of where they were
before. In Sawfish, each screen of a desktop is referred to as a viewport.

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The settings for maximizing windows are as follows:
Maximizing a window dimension always increases the size of that dimension
A window maximized vertically or horizontally will increase to that size even if it fills
the screen.

Raise windows when they're maximized
Maximized windows automatically come to the foreground and receive focus.
Let ignored windows be overlapped when filling windows
If a window is set to be ignored (via the window menu), it will be overlapped by a fill
command.

Lock window geometry while the window is maximized
No resizing of a window can occur if it is maximized.

15.4.8.4. Miscellaneous
This section contains some miscellaneous window settings, including settings for the display
of tooltips.

Windows selected (normally by the Windows menu) are raised
A selected window, either by keyboard shortcut or the desktop window menu, will be
raised with focus.

Unshade selected windows
If a shaded window is selected, it will automatically unshade.
Warp the mouse pointer to selected windows
The pointer is automatically moved to a selected window.
Keep transient windows stacked above
This listbox selects how transient windows are placed. Choose from None, Parents, or
All.

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Update all windows when the default frame style is changed
If you change the window frame style, all windows will be automatically updated.
Automatically reload themes when they are updated
If a theme is edited, the changes are made immediately.
Group transient windows with their parents
Transient windows such as dialogs are automatically placed in the window group of
their parents.

Raise windows when they are unshaded
Windows receive focus and come to the top when unshaded.
To enable window manager tooltips, click the button labeled Display Tooltips for Window
Frames.

Tooltips will be displayed until the pointer leaves the item. You can set them to automatically
disappear by enabling Remove Tooltips After a Period of Time. The amount of time before
displaying and before removing tooltips is set by two input boxes.

You also can set the font used in tooltips, as well as the background and foreground colors.

15.4.8.5. Moving and resizing
The method for drawing windows when they are being moved can be set to opaque or box.
The same options are available for the drawing of windows being resized.

You also can toggle the following settings:
l Raise windows being moved or resized interactively.

l Show the current position while moving windows interactively.
l Show the current dimensions while resizing windows interactively.

15.4.8.6. Placement
This section contains settings for the default placement of new windows. There are placement
policy options for both normal windows and transient windows. Each setting contains a

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listbox with the following options:

l Randomly (transient default)

l Interactively
l Centered
l Centered-on-parent
l Under-pointer
l None
l First-fit
l Best-fit (window default)
l First-fit-or-interactive

If you don't want to allow applications any control over placement, check the box Ignore
Program-specific Window Positions. This setting is disabled by default.

For a first-fit or best-fit policy, you can set an amount of space in pixels to leave between
window edges.

15.4.8.7. Workspaces
Sawfish manages the desktop work area by creating workspaces that can be divided into a
number of different viewable screens, referred to by the GNOME Desk Guide applet as
viewports. Workspaces can be thought of as desktops stacked on top of one another.
Viewports are configured by a grid of rows and columns.

The first option in this window sets the number of workspaces. To define the grid of
viewports, select the numbers of columns and rows you want each workspace divided into
from the available settings.

By default, transient (pop-up) windows will be opened in the same workspace as the window
that spawned them.

The Advanced section contains settings for moving between workspaces. When moving
through workspaces or moving a window, choose the following options for movement at the
ends of workspaces: stop, wrap around, or keep going.

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The easiest way to move among viewports is by using the Desk Guide applet in the GNOME
panel. If you would like to move through screens when moving the pointer on the screen, you
can enable edge flipping. Two checkbox options set up edge flipping:

l Flip to next viewport/ workspace when pointer hits screen edge.

l Flip only when interactively moving a window.

You can specify whether edge flipping takes you to the next viewport (the default) or the next
workspace. If you want to set a delay for edge flipping when the pointer hits the screen edge,
input a number in milliseconds.

15.4.9. Configuring the Enlightenment Window Manager
The Enlightenment window manager is the most common window manager used with
GNOME. Configuring the window manager allows you to adjust the most general behavior of
the desktop, such as mouse behavior, window placement, border styles, and the number of
virtual desktops. You can access the Enlightenment configuration editor from the GNOME
Control Center. Go to the window manager page, select Enlightenment from the list, and click
the Run Configuration Tool for Enlightenment button. This opens the configuration window
shown in Figure 15-7. The Enlightenment configuration tool is composed of the following

sections:

Figure 15-7. Enlightenment configuration tool
15.4.9.1. Basic options
The options on this page set styles of window movement and window focus.

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Move methods

These buttons select how the window is drawn when it is moved. The following styles
are available: Opaque, Lined, Box, Shaded, Semi-Solid, and Translucent.

Resize methods
These buttons select how the window is drawn when it is resized. The following styles
are available: Opaque, Lined, Box, Shaded, and Semi-Solid.

Keyboard focus follows
These buttons determine how "focus" is selected by the actions of the mouse. The
available settings are Mouse Pointer (focus follows mouse), Sloppy Pointer (focus
follows mouse after a delay), and Pointer Clicks (focus is given to window on which a
mouse clicks).

15.4.9.2. Desktops
This section configures your desktop space. You can create a number of virtual desktops, each
using its own screen and switch from one to another as needed. Two sliders allow you to
create the column and row grid of a virtual desktop. Enabling Edge Flip will cause you to
move to the adjacent desktop when the pointer moves across the edge of the current screen.
The delay for the edge flip can be set in milliseconds. The Separate Desktops setting allows
you to set a number of layered desktops (instead of multiscreen panes). Note that the GNOME
Desk Guide applet does not support layered desktops.

15.4.9.3. Behavior
This section contains options for setting additional keyboard focus properties on new
windows and miscellaneous options such as tooltips and placement of pop-up windows. The
Advanced Focus tab contains the following settings:

All new windows that appear get the keyboard focus
New windows automatically receive the keyboard focus.
All new pop-up windows get the keyboard focus
New pop-ups automatically receive the keyboard focus.
Only new pop-up windows whose owner is focused get the keyboard focus
Only pop-ups generated by the window with the current focus receive the keyboard
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focus.

Raise windows when switching focus with keyboard
Minimized windows open when receiving focus.
Send the pointer to windows when switching focus with the keyboard
Mouse pointer moves automatically to windows that receive keyboard focus.
The Miscellaneous tab contains the following settings:
Tooltips
Click the Enable button to allow tooltips to appear when the pointer is over an icon.
You can set the amount of time in seconds for the tooltip to display with the slider
control.

Transient pop-up windows appear together with leader
Displays additional pop-up windows with the window that generated them.
Switch to where pop-up window appears
Automatically switches to the desktop screen where a new pop-up appears.
Display icons when windows are iconified
Displays a small icon on the screen when a window is minimized. Leave this option
disabled as GNOME will handle this functionality with the panel.

Place windows manually
When a new window is opened, the pointer is automatically switched to the activated
move bar of the window. Move the window to the desired location and click to place it.

15.4.9.4. Audio
This page is used to enable sounds in Enlightenment. Sounds for specific actions can be set
manually or set as a group from a theme.

15.4.9.5. Special FX

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This section contains settings for the motion of desktop components, with the following
options:

Window Sliding Methods
The same window drawing options as on the Basic Options page appear here for
sliding window animations, in addition to the following settings:

--Windows slide in when they appear.
--Windows slide about during window cleanup.
--Desktops slide in when changing desktops.
--Window shading speed (pixels/ sec).
Drag bar
Click the button to enable, and set the location to left, right, top, or bottom.
Animate menus
Select this button to enable sliding menu animation.
Reduce Refresh
Select this button to reduce the rate at which the contents of the desktop are refreshed.

15.4.9.6. Backgrounds
This section lets you set the background for each virtual desktop you have. Select the specific
desktop and then choose an image file from the list of available images. You also have an
option button to select No Background. To add an image to the background list, click the Add
New... button and specify the file.

The High Quality Rendering for Background button enables background images to be
displayed at the full resolution and color depth that your display is set to.

Background for desktops that have not recently been viewed can be removed from memory by
enabling the Minutes After Which to Expunge Unviewed Backgrounds from Memory button.
Set the number of minutes to keep them in memory with the slider.

Note that setting a background image in Enlightenment will override the background settings
you have made with GNOME.

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15.4.9.7. Themes
This section allows you to select a theme to apply to the window manager. Themes create a
distinctive and consistent look for windowing components and the background.
Enlightenment themes are installed in the /usr/ share/ enlightenment/ themesdirectory. You can
download any number of user-created themes from http:// e. themes. org. If you use a desktop

theme in GNOME, use a basic window manager theme so you don't create any unwanted
conflicts in your desktop style.

15.4.9.8. Shortcuts
This section allows you to set up keyboard shortcuts for Enlightenment functions. This section
displays a list of predefined shortcuts. You can edit a shortcut by selecting it in the list,
choosing a key modifier, and clicking the Change... button. A pop-up will ask you to press the
key button to use for the shortcut.

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KDE (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

Chapter 16. KDE
Contents:
Desktop Overview
The Panel and Taskbar
The KDE Control Center

KDE, the K Desktop Environment, is an open source software project that aims at providing a
consistent, user-friendly, contemporary desktop for Unix and Linux systems. KDE is not
simply a window manager like fvwm but a whole desktop system that integrates the window
manager functions into its own graphical configuration. The KDE interface makes full use of
drag-and-drop functionality, so you can grab an icon for a text file in the file manager and
drag it to a text editor window to open it. Full network integration of KDE applications allows
you to transparently access files from other computers or FTP sites and manipulate them as if
they were local.

KDE also implements a standard help system based on HTML. Applications that display a
Help button can open a specific help file in the help viewer.

One goal of KDE is to provide the user with system information and configuration through
easy-to-use graphical interfaces of the desktop. The KDE Control Center is a central utility for
desktop and application configuration, as well as a source of information for important system
components. The Information module of the Control Center can retrieve and display status
information for your processor, memory, PCI bus, and network devices.

A wide variety of applications have been developed to take advantage of KDE's features and
provide the user with a wealth of productive applications. The base package comes with
programs such as a mail client, a calendar and organizer, a CD player, image viewers, chat
programs, and many more.

Most Linux distributions ship with KDE and allow you to set it up as the default session
environment when you install the operating system. If you are installing KDE separately,
download and install the KDE packages (you can find them at ftp:// ftp. kde. org, among other
places).

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To set KDE as your desktop environment, look for the X initialization files in your home
directory. Depending on your distribution, look for either .xinitrc, .xsession, or .Xclients in
your home directory. If none of these files exist, create a new .xinitrc file. Edit the file to
remove any window manager references that may exist and add startkde on a line at the end
of the file. Make sure to put the KDE directories in your path. The default package installation
is /opt/ kde. Note that some distributions will use a different KDE path, but it will be
configured by the default setup.

16.1. Desktop Overview
Figure 16-1 shows a typical KDE desktop. The bar across the top edge of the screen is the
taskbar. It is used to keep track of application windows running on the desktop. The panel is at
the bottom of the screen. The panel contains buttons for the main menu, the window list, and
the desktop pager as well as other buttons used to launch applications.

Figure 16-1. The KDE desktop
The desktop displays open application windows and contains icons that can be used to launch
applications with a single click. A number of icons are placed on the desktop by default.
There are two folder icons. One opens the Templates folder, which contains a set of generic
files used to create desktop links. The Autostart folder contains links to applications that are
started automatically every time you log in. The Trash icon is a link to a special desktop
folder to which you can drag files that you want to delete. There are also icons that link to
mounted CD-ROM and floppy drives.

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16.1.1. Application Windows
Each KDE window has a titlebar with common buttons on the right for minimize, maximize,
and close. On the left side of the titlebar, there is a small icon (or a dash, if an icon isn't
specified by the application) and a button that looks like a pushpin. The icon opens the
window menu that contains a number of different functions you can apply to the window,
such as sending it to another desktop. The push pin button is used to stick or unstick the
window to the screen. If you click on the pushpin, the window will be sticky and appear on all
of the virtual desktops. The button appears pushed in when a window is sticky. Click the
button again to unstick a window.

The window menu contains standard window commands: Maximize, Iconify, Move, Resize,
Sticky, and Close. There is also a command that lets you send the window to another virtual
desktop.

16.1.2. kfm --the KDE File Manager
One of the most important KDE applications is kfm. kfm is a graphical file manager and
Internet browser and also controls the workings of the KDE desktop and the icons it contains.
Anytime you click a folder icon, such as the Home folder button on the panel or the Autostart
icon on the desktop, a kfm window opens displaying the contents of the directory. Figure 16-2

shows a kfm window displaying a home directory. Files and directories are shown as icons by
default, but you can use the View menu to view contents with more detail.

Figure 16-2. kfm, the KDE file manager
The kfm interface has its roots in web browsers. The toolbar contains back and forward
buttons for stepping through your selection history, a home button, reload, and stop. The

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Location bar uses URL addressing for both network addresses and local filesystems. HTML
rendering is well-supported in kfm, although not as robust as commercial browsers. If you
don't like the bells and whistles of advanced features such as Java applets and scripting, kfm
makes a perfect, simple web browser. You can even save addresses as bookmarks and use
HTTP cookies.

In addition to file management, kfm is responsible for the functioning of the desktop. When
you log into a KDE session, kfm reads the contents of the Desktop directory. Any files or
folders will be represented as icon links on the desktop. Items contained in the Autostart
folder will be launched as well. kfm uses text files ending in .kdelnk to configure desktop
links. These files are described later.

16.1.3. Adding a Link to the Desktop
There are a couple of ways to add a desktop link. The simplest way is to right-click on the
background and select the New submenu in the pop-up menu. The New menu offers a number
of choices for the type of link to create: Folder, File System Device, FTP URL, Mime Type,
Application, Internet Address, and WWW URL. When you make a selection, a default icon
for that type will appear on the desktop, and the properties window will appear for the link.

The properties window varies slightly for the type of link, but for all links you need to specify
a name for the link file, the label for the icon, and the executable command or file location.
You can also set the permissions for the link file and select a new icon.

The following example shows how to create an application desktop link that opens the Kedit
text editor. First right-click on the desktop and select New Application. A new icon appears
on the screen with the default KDE "gear" graphic and labeled "Application," and the
properties window opens.

The General tab, shown in Figure 16-3, shows the default name of the kdelnk file and other
file information. Change the name of the file to reflect the purpose of the link; in this example,
it is Kedit. kdelnk.

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Figure 16-3. General tab of desktop link properties
Since you created the link file, the permissions allow you to use it. If you want to adjust the
permissions, go to the Permissions tab. The next step is to supply the command used to open
the application. On the Execute tab (Figure 16-4), type in the command, or click the Browse

button to locate the file. Here you can change the icon for the link by clicking the button
showing the current icon. This opens a window that displays a set of default KDE icons found
on your system. Pick the one you like and click OK.

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Figure 16-4. Execute tab of desktop link properties
The final step is to supply the name for the link and a tooltip comment. Fill in the Comment
box on the Application tab (Figure 16-5) with a description of the application. Supply the

name of the link (the label that appears under the icon on the desktop) in the Name box. Click
the OK button to finish the configuration.

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Figure 16-5. Application tab of desktop link properties
For URL or Internet address settings, the properties windows are all the same except for the
default names and icons. These type of links require you to supply the URL address on the
URL tab (Figure 16-6).

Figure 16-6. URL tab of desktop link properties
For a new device link, set the link name and permissions if needed. On the Device tab, supply
the location of the device, such as /dev/ fd3 and the mount point. Specify the filesystem type in

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the Filesystems box (e. g., default, msdos, etc.).

You can also add a link to the desktop by dragging an item from a file manager window. You
can do this with any file or directory. After you drag the item to the desktop, a small pop-up
window asks you whether you want to copy, move, or link the item. Copy simply makes a
copy of the item in the Desktop directory. Move will remove the item from its original
location and place it in the Desktop directory. If you choose link, the desktop icon will contain
a symbolic link that points to the item's current location.

16.1.4. The Desktop Folder and kdelnk Files
Everything that is shown on the desktop exists in the ~/ Desktop folder. If you open this folder
in the file manager, you will see directories for Templates and Autostart, as well as .kdelnk
files for the CD-ROM and floppy drive and any other links you have set. When KDE starts, it
scans the contents of the Desktop directory and creates icons for each item.

Desktop links that launch applications, URLs, or files are configured in the background by
.kdelnk files. These are simple text files that contain all the information that you set for a link
in the link properties dialog boxes. Although all the configuration of desktop links is handled
thoroughly by the configuration pop-up windows, the content of .kdelnk files may be of
interest to advanced users. The following example shows the .kdelnk file for a link to the
Kedit text editor:

# KDE Config File [KDE Desktop Entry] Name[]= Kedit Exec= kedit Type= Application Comment[]= Text editor BinaryPattern= kedit; Kedit Icon= exec. xpm TerminalOptions= Path= Terminal= 0 MimeType= SwallowExec= SwallowTitle= Name[ fi]= Sovellus Name[ hr]= Program Name[ sl]= Uporabniki program Name[ pl]= Aplikacja ...

As you can see, the syntax is simple and straightforward. The items filled in on the properties
windows are listed on each line of the file. The Type line identifies the kind of link file. In this

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example, Kedit is an application. Type= URL would indicate an Internet address link file. The
Name line lists the name of the application, Exec lists the command, Icon identifies the
icon image file, and so on. Unspecified options have empty values. The additional Names
lines are set in the template files and provide alternate names for other languages should you
switch the default language setting for your environment.

15.4. The GNOME Control
Center
16.2. The Panel and Taskbar

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16.2. The Panel and Taskbar
The kpanel program runs the panel and the taskbar. The panel is the control bar across the
bottom of the screen. The panel is used to find and launch applications and navigate among
windows and desktops. It contains the menu, which organizes the installed KDE applications
into submenus; the disk navigator, which provides a menu-driven display of filesystem
contents; and the desktop pager. Additional buttons that open applications, directories, and
URLs can be added to the panel.

16.2.1. The Desktop Pager and Window List
Like most window managers, kwm (KDE's window manager) can divide your workspace into
multiple desktops. Different application windows can be open on each desktop, reducing the
amount of clutter on your screen. You can switch among desktops by using the desktop
buttons on the panel or by using the window list. The panel displays a grid of buttons, one for
each virtual desktop, and their names (One, Two, Three, etc., by default). Clicking on a button
will switch your screen to the corresponding desktop.

If you click the window list icon, it displays a menu divided into sections for each desktop and
items for each window they contain. (The window list is also accessible by middle-clicking on
the desktop background.) For example, if desktop two contains an open file manager window,
you can click on it in the window list, and you will switch to desktop two and activate the file
manager window.

You can configure the number of virtual desktops and their names in the Desktops section of
the Panel configuration module in the Control Center.

16.2.2. The Taskbar
The taskbar runs across the top of your screen and helps you keep track of running
applications. The taskbar contains buttons to identify each open application window. If the
button for an application is clicked, it is the current active window. When you iconify a
window, you can raise it again by clicking its button on the toolbar. If a window has been
iconified, its taskbar button contains a parenthesized text label.

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Whenever you use the arrow buttons to hide the panel, the toolbar displays buttons to access
the main menu, the disk navigator, and the window list. These buttons will disappear when
you show the panel again.

In the panel settings module of the Control Center, you can adjust the positioning of the
taskbar on the screen or choose not to display it at all. You can also set it to autohide so that it
reduces when you aren't using it.

16.2.3. Adding an Application Link to the Panel
The simplest way to add an application button to the panel is by dragging an icon from the
desktop to the panel. This will copy the link from the desktop. Any application listed on the
main menu can be easily added to the panel. From the main menu, choose Panel Add
Application, then select from submenus or items that are listed. The choices you have are the
same items that appear on the main menu.

If you don't want to display some of the default panel buttons, you can use the Panel menu to
turn them off (or on again). The window list and the disk navigator items on the Panel menu
toggle the display of the buttons on the panel. If the item's menu icon appears clicked, the
Panel buttons are enabled. Select it again from the menu to disable the Panel buttons.

16.2.4. Running an Application on the Panel
A swallowed application is a program that you run on the panel instead of in a desktop
window. A swallowed application can be a small utility that monitors network activity or
provides mail notification, for example. In the Execute tab of the properties window, type in
the Swallowing on Panel section with the command to execute and the title that appears in the
titlebar of the application's window. The panel identifies the application to "swallow" by its
window title.

16. KDE 16.3. The KDE Control
Center

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16.3. The KDE Control Center
The KDE Control Center contains a number of configuration tools, called modules, that allow
you to configure and view information about your system. You can configure the desktop, the
window manager, input devices, and any other important part of your system here. The
Control Center is split into two windows: the left window shows a hierarchical list of installed
modules, and the right window displays them when they are selected. (You also have the
option to display each module in its own window. Go to the Options menu and click the
Swallow Modules entry, which is checked by default, to unselect it.)

16.3.1. Applications
The Applications modules set preferences for important KDE components, such as the login
manager, kfm, and the panel.

16.3.1.1. Login manager (root only)
The KDE login manager is the program that controls the graphical login screen. This module
lets you configure the graphical style of the login screen, as well as set some default display
options, such as prelisted users and available session environments.

The Appearance tab lets you edit the greeting string displayed on the login screen and choose a
logo. A drop-down box offers you a choice of the GUI style of the login screen: either
Windows or a Motif style. The Language option on this tab lets you select the default character
encoding for the login manager.

The Fonts tab lets you choose the font style and size for the Greeting, Fail, and Standard
screen messages. Select which type you want to configure from the drop-down list and click
the Change Font button. The pop-up window shows a list of available fonts and lets you set the
point size. Click the OK button to close the pop-up window. The font you have chosen is
displayed in the Example area of the tab.

The Background tab lets you select the background for the login screen. Like the desktop
background, you can choose a color or wallpaper to use.

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The Users tab allows you to show a list of users on the login screen. The users are listed by
username with a logo above the login boxes. A user can simply click her logo to automatically
enter her name into the login box, but she still must supply her password. The tab contains
listings for all users, selected users, and no-show users. You can select names from the lists
and use the arrow buttons to move them from one box to another. Two options are available
for who to display on the login screen. You can place names in the selected users list and click
the Show Only Selected Users button. Or, you can edit the all users list and click the Show All
Users But No-Show Users button. No-show users are user IDs that are used to control access-restricted
system resources (e. g., root, news, and nobody).

The Sessions tab configures session settings. The drop-down list at the top sets who is allowed
to shut down the system. You have the choices None, All, Root Only, and Console Only. The
Commands section allows you to set the commands used for shutdown and restart. The
Session Types section configures the list of session types that a user can log into from the
login screen. The Default list contains the various environments that are installed on your
system such as KDE and GNOME. You can add a new type or remove a type from the listing.

16.3.1.2. File manager
This module contains configuration settings for kfm, the KDE file manager and browser. The
first tab contains the font settings. Set the font size used in the file manager to either small,
medium, or large by selecting the corresponding button. You can set the font styles used for
displayed files or web pages with the Standard Font and Fixed Font settings. You can also set
the character set to use.

The Color tab allows you to set the colors used for background, text, and links. You can set
two colors for URL links: one for new links and one for links that have already been followed
(as recorded by the URL history). There are also settings to change the cursor when it is over a
link, underline links, and override HTML-specified colors with the default colors set on this
tab.

The Other tab allows you to enable URL-specific settings. If you have set certain properties to
view a certain URL or local directory, like menu bar display or the view settings, you can have
them saved for the next time you visit that URL. The Tree View Follows Navigation button
causes the directory tree in the left pane of the file manager to match the current open folders
in the right pane. The final settings on this page allow you to select the default programs the
file manager uses for a terminal when you use Open Terminal from the File Menu and the
editor used to view the source of documents.

16.3.1.3. Web browser
This module configures settings used for kfm's web browsing functionality.
If your system is behind a firewall, you may need to use a proxy server for HTTP and FTP
services. The Proxy tabs lets you enable the use of a proxy and configure it. Check the Use

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Proxy box, and supply the hostname or IP address for the proxy server and the port number to
use. Some sites may not work properly when accessing them through a proxy server. The No
Proxy For: box lets you specify a list of hostnames and domains that will not be accessed via
the proxy server.

The HTTP tab sets a few of the parameters sent in HTTP requests by the browser. The Accept
Languages box contains a list of two-letter abbreviations used to indicate the language that the
browser can accept. The abbreviations, like en for English and fr for French, can be comma-or-space
separated. The order of the list determines the preference of language. The Accept-Language
HTTP request header is configured with this setting.

The Accept Character Sets box contains a list of character sets that the browser is capable of
receiving. (This sets the Accept-Charset HTTP request header.) The list can accept the
standardized character set strings, separated by spaces or commas. The Assume HTML button
tells the browser to render as HTML documents whose type is not fully specified from the
server response header.

The User Agent tab allows you to specify the user-agent string reported by the browser for
sites that may not recognize kfm, or anything that's not a major commercial web browser. The
user-agent string contains the name and version number of the client program making the
request. The default for kfm at the time of this writing is "Konqueror/ 1.1.2". To set a different
string for a specific server, type the server name in the On Server box and supply the user-agent
string in the Login As box. Click Add to save this setting. All settings will be listed in
the Known Bindings box. If you want to remove a setting, select it from the list, and click the
Delete button.

The Cookies tab configures how kfm will manage cookies. Cookies are not used at all unless
you check the Enable Cookies box at the top of the tab. You should set the default cookie
policy to either accept all cookies, reject all cookies, or prompt for action each time a cookie is
received. You can specify the policy for individual domains as well. Type the domain into the
Change Domain Accept Policy box, and specify Accept, Ask, or Reject for the policy. Click
the Change button, and the setting is saved. You will see it listed in the Domain Specific
Settings list. If you would like to remove a setting, select it from the list and click the Delete
button.

16.3.1.4. Panel
The panel configuration module controls the panel, the toolbar, virtual desktops, and the disk
navigator.

The Panel tab contains settings for the location of the panel. You can choose to place it at the
top, bottom, left side, or right side of the screen by clicking the appropriate radio button. Three
settings are available to set the size of the panel to either Tiny, Normal, or Large. You also
have choices for how the taskbar is displayed. If you do not want the taskbar to be displayed at
all, click the Hidden radio button. If you want the taskbar displayed fully across the top or

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bottom of the screen, click either the Top or Bottom button. If you choose the Bottom option,
the taskbar will appear just above the panel. Finally, the Top/ Left option displays the taskbar at
the top-left corner of your screen, with window buttons stacked on top of each other.

The Options tab, shown in Figure 16-7, is divided into three sections. The Menu Tooltips
section contains a button to enable tooltips to be shown on menu items. You can use the slider
to set the amount of time that the pointer is held over the item before the tooltip appears. The
Visuals section allows you to set the panel and taskbar to autohide (i. e., disappear when not
being used). Enable these settings by clicking the Auto Hide Panel and Auto Hide Taskbar
buttons. Each option has two slider settings if autohide is enabled. The Delay slider sets the
amount of time after use (after the pointer has left the panel/ taskbar) that the panel will reduce.
The Speed slider sets how fast or slow the panel or taskbar will open and hide. The Animate
Show/ Hide setting enables the panel to use a sliding visual effect when you show or hide it
with its side arrow buttons. The slider sets the speed of this animation.

Figure 16-7. Panel options configuration
The Options tab contains the following additional settings:
Personal Menu Entries First
Check this box to display your personal menu section instead of the default system
menu at the top of the main menu. The system menus will be contained in the default
submenu.

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Menu Folders First

Check this box if you want folders to appear at the top of your personal menu, above
individual items. This setting can be overridden by customizing the menu order with
the menu editor.

Clock Shows Time in AM/ PM Format
This option enables AM/ PM designation on your panel clock. Otherwise, the hour
listing will range from 00 to 24.

Clock Shows Time in Internet Beats
This option allows you to have the panel clock display the Swatch-created time format,
which divides a day into 1000 beats, in the GMT+ 1 time zone.

The Desktops tab sets the number of virtual desktops you can divide your workspace into. The
default is 4, and you can use up to 8. The Visible slider selects the number of desktops (you
can choose only even numbers). The desktops are listed, numbered 1 through 8. If enabled, the
desktop listing has a usable textbox next to it. You can type in a label for the desktop that will
be used in the pager display on the panel. The Width slider sets the width of the pager buttons
shown on the panel.

The Disk Navigator tab allows you to configure the disk navigator shown on the menu and the
taskbar. The History section of this tab has two buttons: Edit Personal and Edit Shared, which
allow you to edit the contents of the Personal and Shared sections of the disk navigator from
the file manager.

The Edit Personal button opens kfm in the ~/. kde/ share/ apps/ kdisknav directory. This folder in
the user's home directory contains kdelnk files for the items displayed in the Personal section
of the disk navigator. The Edit Shared button opens /usr/ share/ apps/ kdisknav in kfm, which
contains kdelnk files for the contents of the Shared section. This directory can be edited only
by root; other users will have this button disabled.

Additional options set the number of folder entries and file entries displayed in the Recent
section of the disk navigator and the maximum number of files that can be displayed in a
folder.

The Options section of the Disk Navigator tab contains buttons for the following settings:
Show Dot Files (which shows the hidden files that start with a dot), Show Shared Section,
Show Recent Section, Show Personal Section, Show Option Entry, and Ignore Case When
Sorting. There is also a selection for the default terminal application to use.

16.3.2. Desktop

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The Desktop modules set preferences for the visual display of your environment. You can
individually set the background, fonts, or window colors or use the Theme Manager to
configure all of the settings from an installed package.

16.3.2.1. Background
This module sets the desktop background. It allows you to specify a background for each
virtual desktop or just one for all of them. Select the desktop you want to configure from the
list, or check the Common Background box. You can use colors or a wallpaper image for your
background. The One Color setting applies a solid color to the background. The Two Color
setting lets you choose a blend of two colors. Select the colors you desire by clicking on the
color bars. The Setup button opens a dialog box for two-color settings. You can select to blend
the colors vertically, horizontally, or with a pattern.

If you would like to use an image file as wallpaper on the background, select it from the drop-down
list, or click the Browse button to look for the image on the filesystem. The
Arrangement setting determines how the image file is laid out. You can choose from the basic
tiling layout to such effects as symmetrical mirroring. You can also choose a random
background. A new image file and settings will be used every session.

16.3.2.2. Borders
This module sets up border properties for windows and the screen. Active desktop borders
enable you to switch between desktops by moving the mouse pointer to an adjacent screen
edge. Check the box to enable this setting. The Desktop switch-delay slider sets a delay time
for the switch to the adjacent desktop. Set this time to a comfortable setting that doesn't cause
an unwanted desktop switch every time you move the pointer to the screen edge. Check the
Move Pointer Towards Center After Switch box if you want the pointer to go to the center of
the screen when you switch desktops.

Magic Borders sets up "snap-to" zones around windows and at the edge of screens. You can
set the width of zones, in pixels, in which moved windows will be placed.

16.3.2.3. Colors
The Colors module allows you to select the colors for the various window widgets, the
components used to build windows. You can select the colors based on a scheme installed on
your system. Available schemes are listed. Select one from the list, and click Add to change
the color scheme. You can also set colors for individual components. The top of the tab shows
sample windows components. Click on the component you want to configure, such as the
active titlebar or window background to select it. You can also select a component from the
widget color list. Click the color bar under the list to open the color selector dialog box and
choose your color. You can also set the contrast of the component with the Contrast slider.

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16.3.2.4. Fonts

The Fonts module sets the default fonts used in your display. You can set the font for the
following listed selections: the general font, fixed-width font, window titles, panel buttons, and
the panel clock. You can set the typeface of the font from the drop-down list and choose if you
want it either bold or italic. Select the point size of the font, and optionally change the
character set used. A sample of the selected font is displayed at the bottom of the window.

16.3.2.5. Desktop icons
This module controls the display of icons on the desktop. Icons are placed along invisible grid
lines on the desktop. The grid spacing sets the number of pixels surrounding each icon. Two
controls allow you to set the horizontal grid spacing and the vertical grid spacing.

Labels for icons are displayed with transparent backgrounds, allowing the background to be
visible underneath them by default. Uncheck the Transparent Text for Desktop Icons box if
you would like to view the background box of the label. You can set the color of text labels by
clicking the Icon Foreground Color button. If backgrounds are nontransparent, you can choose
their color by clicking the Icon Background Color button.

The final setting on this tab allows you to show hidden files (files that begin with a dot) on the
desktop.

16.3.2.6. DPMS
DPMS stands for Display Power Management System. If your hardware supports power
management, you can enable it by clicking the DPMS enabled button. Now you can set the
amount of idle time before the system goes to standby mode, then suspend mode, and finally
turns off.

16.3.2.7. Theme manager
Themes provide an overall visual style to your desktop, instead of you having to configure
items individually. A theme can determine the color scheme of windows, the font styles, icons,
the background, and even sound events for your desktop. A couple of themes are installed by
default with KDE, and many more are available for downloading at http:// kde. themes. org.

TheInstaller tab, shown in Figure 16-8, lists the themes you have installed on your system.
These include global themes, which are stored in the /share/ apps/ kthememgr/ Themes
directory of your default KDE directory, and local themes, stored in
~/. kde/ share/ apps/ kthememgr/ Themes in your home directory. Local themes are themes that
are installed or customized by the user and stored in his home directory. The user is able to
edit and save local themes. Global themes cannot be altered by individual users.

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Figure 16-8. Theme Manager installer
If you select a theme from the list, a sample desktop image using the theme is displayed on the
tab, with a short text description. If you would like to apply a new theme, select from the list
and click the Apply button. The selected theme will be copied to the user's theme manager
work directory (~/. kde/ share/ apps/ kthememgr/ Work).

You can also manage installed themes on the Installer tab. To install a new theme that you
have downloaded, click the Add button. Specify the filename and location of the theme's .tgz
file in the pop-up dialog box and click OK. The Save button lets you save the currently
configured theme as local or save a global theme as local. The Save As button saves the
currently configured theme as a separate local package without altering the original theme.
The Create button works similarly, allowing you to copy your current working theme as a new
local theme package. The Remove button deletes a local theme or inactivates a global theme.

The Contents tab shows the components that are configured by a theme. A theme may not
have settings available for all the listed components. If a theme configures a specific
component, it is listed as available. Otherwise, the component is listed as empty. Use the
checkboxes to select which theme components you want to use. If you choose to not activate a
specific component, information on that component from a previous theme will be used if its
information is still in the theme manager work directory. If you don't want this to happen,
activate the component, even if it is listed as empty, and default settings will be used.

The About tab shows you author and version information for a selected theme.

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16.3.2.8. Language
The Language module sets the preferred locale (language) settings for your programs. The
drop-down lists allow you to choose first, second, and third choices for the language, if
programs make them available.

16.3.2.9. Screensaver
This module sets up your screensaver. A list of available screensavers is shown with a preview
window. If you do not want to use the screensaver, select No Screensaver from the top of the
list. Otherwise, select the screensaver you want to use. The Setup button opens a dialog box
that contains specific configuration settings for each screensaver. For a full-screen test of the
screensaver, click the Test button.

The Settings section allows you to set the amount of time the system is inactive before the
screensaver starts. Type in the number of minutes in the Wait For box to set this time. If you
check the Require Password box, the user must supply her password before returning to the
desktop. You can also check the box to Show Password as Stars to display the password text
as asterisks, instead of the field being blank. The Priority control lets you adjust the priority
that the screensaver process has when it is run. If you have lots of important server activity, for
example, set the priority to low so the performance of other programs will not suffer.

16.3.2.10. Style
The Style module contains a couple of settings for the display of windows and icons. Draw
Widgets in the Style of Windows 95 enables window components to have a similar look to
those used in Windows. The Menu bar on Top of the Screen in the Style of MacOS setting
places a window's menu bar across the top of screen. Apply Fonts and Colors to Non-KDE
Apps will apply the styles you've chosen to programs that were not written for KDE.

The Icon Style section allows you to set the size of icons to either Normal or Large. You can
set the size for icons in the following locations: on the panel, in the file manager and desktop,
and at all other locations.

16.3.3. Information
The Information modules allow you to view status information about various system
components. There are no configuration settings here, but if you need to see information about
your processor or what PCI devices you have installed, use these modules. Information is
provided for the following system components:

l Devices

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l DMA-Channels

l Interrupts
l IO-Ports
l Memory
l Partitions
l PCI
l Processor
l SCSI
l Samba Status
l Sound
l X-Server

16.3.4. Input Devices
The modules here control the configuration of the keyboard and mouse.

16.3.4.1. Keyboard
This module configures keyboard repeat. Select the On option to enable keyboard repeat, and
use the slider to set the volume of keyclicks. If you don't want keyclicks, set the slider to 0.

16.3.4.2. Mouse
This module configures the movement and button layout of your mouse. The Acceleration
slider sets the speed at which the pointer moves on your screen when you move your mouse.
The Threshold slider set the distance (in pixels) that the mouse must move before pointer
movement occurs. The Button Mapping options let you choose if you use the mouse with your
right hand or left hand.

16.3.5. Keyboard Shortcuts
You can choose the scheme used for shortcuts by selecting the KDE defaults or the current
scheme if you have customized the shortcuts. The bottom section of the tab allows you to edit

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the selected keyboard shortcut. You can choose no key for the action, the default key, or a
custom key. If you want to customize a key, check the box for the modifier you want to use
(Shift, Ctrl, or Alt), or unselect all of them if you don't want a modifier. Then click the key
button and press the key on the keyboard that you want to use. Click the Save Changes button
if you want to save the change to the current scheme.

16.3.5.1. Global keys
The following table lists the keyboard combinations that cause global window events:

Keys Action
Alt-Esc, Ctrl-Esc Displays a list of currently running applications
Alt-Tab, Alt-Shift-Tab Switches among windows on the desktop
Ctrl-Tab, Ctrl-Shift-Tab Switches among virtual desktops
Alt-F2 Opens the single-command-line utility
Alt-F3 Opens the control menu of the current window
Alt-F4 Closes the current window
Ctrl-F[ 1.. 8] Switches to the correspondingly numbered virtual desktop
Ctrl-Alt-Esc Kills the current window

16.3.5.2. Standard keys
The standard key mappings are shortcuts to common actions that you would find in most KDE
programs like the file manager or graphical text editor.

Keys Actions
Ctrl-W Close
Ctrl-C Copy
Ctrl-X Cut
Ctrl-End End
Ctrl-F Find
F1 Help

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Ctrl-Home Home
Ctrl-Insert Insert
Ctrl-N New
PageDown Next
Ctrl-O Open
Ctrl-V Paste
Ctrl-P Print
PageUp Prior (or Previous)
Ctrl-Q Quit
Ctrl-R Replace
Ctrl-S Save
Ctrl-Z Undo

16.3.6. Sound
The modules contained in this section configure the keyboard bell and other system sounds.

16.3.6.1. Bell
This module configures the system bell.
The Volume slider sets the volume of the bell. The Pitch slider sets the tone of the slider in Hz.
You can set the duration of the system bell with the Duration slider control. To listen to your
settings, click the Test button.

16.3.6.2. System Sounds
Desktop themes can set .wav audio files to play for specific events, such as raising a window
or clicking a dialog button. This module allows you to enable and configure sound events.
Check the Enable System Sounds checkbox to enable sound events.

The tab contains two panes. The left pane contains the Event list of the available actions that
you can apply a sound to. The right pane contains a list of .wav files that you can assign to
actions. Selecting an event will highlight its currently assigned sound in the Sounds list. To set
a sound event, select an action from the Events list, then select a sound file from the Sounds
list. The Test button allows you to listen to a selected sound. Click the Apply button to save

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your settings.

16.3.7. Window Behavior
The modules contained in this section allow you to set the look and functions of window
titlebars, mouse button actions, and focus and placement policy.

16.3.7.1. Advanced
The Keyboard and Mouse section of the Advanced tab contains the following settings:
Ctrl-Tab walks through desktops
This checkbox sets the Ctrl-Tab key combination to switch through your virtual
desktops. It is checked by default.

Alt-Tab is limited to current desktop
This checkbox restricts the action of the Alt-Tab key combination to switch through
windows on the current desktop only. It is checked by default.

Alt-Tab mode
This setting describes the style of using Alt-Tab to switch through windows. The KDE
setting uses a graphical style. When you press Alt-Tab, a window appears indicating
the current window and other available windows. The CDE setting switches directly
without a graphic.

Grab the Right Mouse Button
This setting is on by default. It sets the control of the right mouse button to KDE by
default. Some non-KDE applications require control over the right mouse button. If you
need control for these applications, unselect this setting.

The Filters section of the Advanced tab contains settings that let you customize window styles
or functions for application windows based on their titles or classes. The drop-down box
contains a list of settings that you can define for a filtered window. After the Windows Will
label, you can choose the following settings:

l Have tiny decorations

l Have no decorations
l Never gain focus
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l Start as sticky
l Be excluded from session management

Select a setting, then define the window in the next section, which begins with If They Match
the Following. Here you have two boxes, Titles and Classes. You can define one or both
properties. Put the title of the application window in the Title box and the application's class
name in the Classes box. (This is usually the capitalized name of the application, preceded by
an X, for example, XEmacs for an Emacs window.) You can specify more than one title or
class for a window setting.

16.3.7.2. Buttons
This module configures the layout of buttons that appear on the titlebars of windows. There
are five buttons: minimize (dot), maximize (square), sticky (pushpin), close (X), and menu
(dash or application-specified icon). Each button has three placement options, specified by
radio buttons: left, right, or off. You can place no more than three buttons on one side of the
titlebar.

16.3.7.3. Mouse
This module configures the actions of mouse buttons on the various window components.
Drop-down boxes contain several options, such as raise or lower, for the left, middle, and right
buttons, as shown in Figure 16-9. Select from the following options in each category:

For active titlebars and frames
Raise
Lower
Operations menu
Toggle raise and lower
For inactive titlebars and frames

Activate
Activate and raise
Activate and lower
For an inactive inner window

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Activate, raise, and pass click

Activate and pass click
Activate
Activate and raise
For titlebars and frames of inner windows

Move
Toggle raise and lower
Resize
Raise
Lower
Nothing

Figure 16-9. Mouse button configuration settings
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16.3.7.4. Properties

This tab sets windows options and the placement and focus policy. The Windows section of
the tab has three settings:

Vertical maximization only by default
Check this box to cause the maximize window command to expand a window only to
the full screen height, but leaving its width unchanged.

Display content in moving windows
Check this box to enable the display of window contents when the window is moved.
Display content in resizing window
Check this box to enable the display of window contents when the window is resized.
Resize animation
This slider controls the animation of windows that are maximized or minimized.
Setting the slider all the way to the left (None), disables animation, and windows will
maximize or minimize instantly. You can set the speed of the animation faster by
setting the slider farther to the right.

The Placement Policy section of the tab contains a drop-down box with five options for
determining the initial placement of new windows on the desktop:

Smart (default)
This setting uses a placement scheme that attempts to keep windows as uncluttered as
possible.

Cascade
This setting attempts to place windows in a cascaded pattern, with a set of offset
positions available on each desktop.

Interactive
This setting enables the "allowed overlap" setting. If a window can be placed on the
desktop without overlapping another by the specified percentage, it will be placed
automatically. If the overlap exceeds the setting, you will be given manual control of
the window placement.

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Random
This setting randomly places a new window on the desktop.
Manual
This setting opens a window with the mouse pointer activated in move mode on the
titlebar. Move the window to the desired position and click once to place the window.

The Focus Policy section sets the policy for giving a window keyboard focus and an active
titlebar. The drop-down box contains four focus styles. The default is Click to Focus, which
gives a window the keyboard focus and brings it to the foreground only when you click on it.
The remaining settings follow the mouse and activate the Auto Raise and Click Raise options.

Click to focus
The default focus policy requires a mouseclick in a window to give it focus and raise it
(bring it to the foreground). This setting uses a graphical Alt-Tab style to switch
through windows on a desktop.

Focus follows mouse
This setting causes a window to receive focus when the mouse pointer enters it. The
window will not come to the foreground unless the Auto Raise button is checked. The
window will maintain focus until the pointer enters another window.

Classic focus follows mouse
This setting is similar to the Focus Follows Mouse setting, except that the window loses
focus when the mouse pointer moves out of it. If the pointer is not in a window, no
window has focus. Also, Alt-Tab switches directly among windows, without showing
the graphical listing of windows.

Classic sloppy focus
This setting is similar to Focus Follows Mouse, with focus remaining in a window even
when a mouse pointer leaves it. The only difference is that the nongraphical Alt-Tab
style is used.

For any of the nondefault settings, you need to check either the Auto Raise or Click Raise
boxes to be able to raise windows to the foreground. Click Raise raises a window when you
click on it. Auto Raise raises a window after a short delay, which you can set with the Delay
slider.

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16.3.7.5. Titlebar

This tab contains many settings for the appearance and action of window titlebars. The Title
Alignment sets the positioning of the window title in the titlebar to either Left, Middle, or
Right.

The Appearance settings adjust the graphical decoration of the titlebar:
Shaded Vertically
Uses a two-color background in a top-to-bottom gradient.
Shaded Horizontally
Uses a two-color background in a left-to-right gradient.
Plain
Uses a solid color for the background.
Pixmap
Uses a pixmap image for the titlebar background. This enables the Pixmap settings,
which allow you to choose images for both active and inactive titlebars. If you don't
want the image to appear under the window title text for better clarity, check the box
labeled No Pixmap Under Text.

The checkbox labeled Active Title has Shaded Frame gives a shadowed, 3D appearance to
active titlebars.

The Mouse Action options specify the action of double-clicking on a window titlebar. The
available options are (Un) Shade (the default), (Un) Maximize, Iconify, (Un) Sticky, and Close.
The settings identified with (Un) are toggle settings.

Title animation can be enabled to display a sliding titlebar animation when a title is too long
for the display area. The slider sets the speed of the back-and-forth motion.

16.2. The Panel and Taskbar 17. An Alternative Window
Manager: fvwm2

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An Alternative Window Manager: fvwm2 (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

Chapter 17. An Alternative Window
Manager: fvwm2
Contents:
Running fvwm2
Configuration Files
A Modular Approach
How to Implement Window Manager Customizations
A Quick Tour of the fvwm Environment
Specifying Click-to-Type Focus
Raising the Focus Window Automatically
Changing the Size of the Desktop
Having Multiple Desktops
Making the Same Window Appear on Every Page
Starting Windows on Different Desktops and Pages
If It's Too Hard (or Easy) to Move the Pointer Between Pages
Adding Keyboard Shortcuts
Customizing Menus
The FvwmWinList: Switching the Focus

Among the more appealing characteristics of a Linux system are its flexibility, its
independence from industry-dominating standards, and the degree of control a user has over
his own working environment. Most flavors of Linux come with a default desktop
environment replete with handy tools and menus and a consistent look and feel. The most
widely used of these desktop environments are GNOME and KDE, the customization of
which are detailed in Chapter 15, "GNOME", and Chapter 16, "KDE", respectively.

Both of these environments put a PC-like wrapper around what is basically a no-frills Unix-based
system suitable for personal computers. For some people this is a good thing. But if you
don't want a lot of dialog boxes cluttering up the screen, and you're comfortable editing
configuration files to customize your environment, you might instead try the fvwm2 window

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manager.

fvwm2 is the latest generation of a window manager called fvwm, but in neither case has it
been entirely clear what fv stands for. Virtual seems a reasonable guess for the v. fvwm
predates both GNOME and KDE as a program that can provide multiple virtual screens to
expand your desktop real estate. But the meaning of the f in fvwm has led to much
speculation. In fact, among the latest group of the program's developers are a number of cat
lovers who claim the f stands for feline.

The first important concept you should understand in order to work with fvwm is that your
desktop can be larger than the area of your screen. In fact, fvwm2 can let you have acres of
desktop real estate in the form of virtual screens, or pages. In a typical default environment,
you might have a single desktop composed of four virtual screens/ pages arranged in a two-by-two
grid.

You can run applications on any of the screen pages you want and navigate the entire desktop
in a variety of ways. And if the default environment doesn't suit you, well, you can specify a
grid of any size you like. How about three screens across and two down? No problem.

And if that isn't enough space for you, you can also have multiple desktops, each composed of
multiple pages! You might use separate desktops for different applications or different
projects, whatever you like. fvwm2 provides the tools for you to navigate whatever space you
design.

fvwm2 is also customizable in a vast number of other ways, some of the more significant of
which this chapter will summarize. What it all boils down to is maximum workspace and
maximum flexibility.

17.1. Running fvwm2
Most flavors of Linux will come with some reasonably current version of fvwm2. If you're
running GNOME or KDE, the easiest way to switch over to fvwm2 is to:

1. Invoke the window manager in your X client's startup file. (Depending on your
environment, this file may be called .xinitrc, .startx, .xsession, or .Xclients.)

2. Then restart X.
Here is an excerpt from a simple startup file that has been edited to run fvwm2:
xterm -geometry +50+ 0 & xterm -geometry -0+ 0& fvwm2 & xterm -title login -iconic

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Although hypothetically you can run fvwm2 along with GNOME or KDE, they provide
greatly overlapping functionality. What you get is an ugly hybrid and not fvwm at all.

16.3. The KDE Control
Center
17.2. Configuration Files

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17.2. Configuration Files
The key to how fvwm2 works is the configuration file it reads at startup or restart. The
systemwide configuration file is called system. fvwm2rc and usually lives in the directory
/etc/ X11/ fvwm2.

The typical system. fvwm2rc file that gets distributed should create a simple but perfectly
workable environment. We'll take a look at one in the next section. There's no guarantee that
the file on your system will create the same layout, but you'll get the idea.

If you want to customize fvwm2 to suit your needs, you need to make a copy of
system. fvwm2rc called .fvwm2rc and put it in your home directory. This personal
configuration file takes precedence over the systemwide file. You edit your .fvwm2rc file to
adapt the window manager to your needs.

There are a few simple rules in editing your .fvwm2rc file. First, any line that begins with a
pound sign (#) is a comment (i. e., it is not interpreted as part of the window manager
definition). Second, a plus sign (+) at the beginning of a line means to repeat the first terms
from the previous line. The section "Making the FvwmWinList Part of Your Default
Environment," later in this chapter, illustrates the use of this syntax. The final thing to keep in
mind is that it will make life simpler if you weave your own definitions into the file,
respecting its current contents and their order. So, for instance, if you decide to define some
function keys, put your new lines in the section of the file that already deals with keys.

In terms of fvwm2 customization, there's some good news and some bad news. The good
news is that you can make an extraordinary number of changes to the way fvwm2 looks and
operates. That's also the bad news. The window manager has dozens of configuration options,
many very handy and easy to use, others complex and even arcane. The sum total can make
the configuration file syntax daunting to anyone who isn't accustomed to serious tinkering. In
fact, you could get dizzy considering the possibilities.

The fvwm2 manpage gives all of the configuration options and illustrates their use; you may
also want to consult the manpages for the so-called fvwm2 modules, introduced in the next
section. The web site http:// www. fvwm. org is the definitive source for window manager

documentation, news, source code, and updates.

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This chapter should help you cut to the chase in performing some of the more basic and useful
customizations, as well as some tricky but handy upgrades.

17. An Alternative Window
Manager: fvwm2
17.3. A Modular Approach

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17.3. A Modular Approach
fvwm2 has been designed to allow the interested programmer or programmer wanna-be to
devise new components, known to insiders as modules. A typical module is the Pager
(FvwmPager), which provides a map of the desktop space and a way to navigate it, as we'll
see a little later in the chapter. The Pager is a default module in just about any environment.

The FvwmWinList is another useful module. Though not as ubiquitous as the Pager, it is just
as useful. The FvwmWinList is a small window that provides a list of all the windows running
on all pages of all desktops. The WinList is another navigation tool, allowing you to switch
the pointer focus to any application you have running and to switch the screen view so that
you can use that application. More about this later.

A module is actually a separate program from fvwm2 but works in concert with it, passing
commands to be executed to the window manager. Many configurations of fvwm2 have a
Root menu with an FvwmModules submenu from which you can start certain of these
programs. (Naturally the list of modules on the menu is configurable.) You might also edit
your .fvwm2rc file to run modules in other ways (when you type certain keys, when other
events happen, etc.).

Since a module is a separate program, users can write their own modules without adversely
affecting fvwm2. Note, however, that you must configure fvwm2 to start the module process;
you cannot start one from the command line. Note that while some modules, like the Pager,
are intended to be used for the entire session, others simply perform a function and exit (e. g.,
RefreshWindow). Since modules are programs in their own right, many of them have their
own manpages too.

17.2. Configuration Files 17.4. How to Implement
Window Manager
Customizations

Copyright © 2001 O'Reilly & QKFIN. All rights reserved.
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Edition

17.4. How to Implement Window Manager
Customizations

If you edit your .fvwm2rc file, simply restart fvwm2 to have the changes implemented. In
most environments, there will be a menu item that restarts the window manager. The vanilla
setup we started with offers the item Exit fvwm2 on the Root menu. If you select that item,
you'll get a submenu titled Really quit fvwm? and several items including Restart fvwm2.
When you select Restart fvwm2, your configuration changes should be implemented. A
slower but just as effective way is to quit the X session and start it again (presuming your
session startup file includes fvwm2).

17.3. A Modular Approach 17.5. A Quick Tour of the
fvwm Environment

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Linux in a Nutshell, 3rd
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17.5. A Quick Tour of the fvwm Environment
In any desktop environment with multiple virtual screens/ pages, you can work on only a
single screenful at a time. But fvwm2 makes it easy to switch the view between pages, run
applications on different pages, and move applications between them. If you refer to a
particular window all the time, you can even arrange for it to appear on every page of every
desktop. (We'll come back to this concept of "sticky" windows.) And you're not limited to
viewing a page proper or keeping a window entirely on a single page.

Notice the long horizontal box in the bottom right corner of our sample environment (Figure
17-1). This box is the FvwmButtons module (also called the button bar). FvwmButtons is
generally used to house a number of tools and applications to which the user needs frequent
access. Often these are other fvwm modules.

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Figure 17-1. A typical fvwm2 environment
In our sample configuration, FvwmButtons contains two other modules: the Icon Manager
(FvwmIconMan) on the left side of the box and to its right, the Pager (FvwmPager). At the far
right of FvwmButtons you'll also see three small application windows: xbiff (a mailbox that
indicates when you have new messages), xclock, and xload (a graphic representation of your
system's workload).

The Icon Manager and the Pager are tools that let you both monitor what's happening in your
environment and manipulate the windows running there. The Icon Manager shows an entry
for every conventional window currently on your display. If that window is iconified, the Icon
Manager entry is preceded by a square that has a three-dimensional appearance. You can
iconify and deiconify any window on the current page by clicking the first pointer button on
the corresponding entry in the Icon Manager. (The Icon Manager always shows the windows
on the current page; for a similar tool that reflects what's running on every page on every
desktop, check out the FvwmWinList, described later in this chapter.)

Think of the Pager as a tiny mirror of your entire desktop( s). In a typical default environment
of a single desktop composed of two-by-two screen pages, the Pager shows a small grid of
four partitions separated by dotted lines. These partitions correspond to the desktop's four
virtual screen pages. (If you configure for multiple desktops, a solid line is used to show the
border between desktops. The section "Having Multiple Desktops," later in this chapter, tells

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you how to set this up.)

Each application you run appears in miniature in the Pager window. Applications with small
windows are fairly hard to spot in miniature, but a blip representing them is there if you look
closely. The miniature version of a larger client, like xterm, should have a readable label.

Whatever operations you perform on windows on the desktop --e. g., move, iconify, resize,
and so on --are mirrored in the Pager. But the Pager is more than a monitor of activity; it's
also a tool. Thus, you can move the miniature versions, and the actual windows will be
moved. The Pager can also help you move windows between pages and desktops and select
the area to be displayed on your monitor (which does not have to correspond to a page
proper).

In addition to the desktop tools, fvwm2 is commonly configured to provide a slew of
cascading menus beginning with the Root menu. Clicking the first pointer button on the root
window should reveal this menu. The Root menu is usually a good way to start a new terminal
emulator window. If you start with the default environment for your system, the Root menu is
likely to have submenus like Fvwm Modules, Fvwm Window Ops (which offers items like
moving, resizing, and closing windows), Fvwm Simple Config Ops (for changing focus
policies, how paging works, etc.), and Exit Fvwm (for restarting or exiting the window
manager, starting another one, etc.).

This chapter assumes you know how to perform basic window manager operations. We're not
going to teach you how to use the Pager or all the menu items. But we will show you how to
change the number of desktops the Pager shows, add menu items, configure keyboard
shortcuts, and make useful customizations.

17.4. How to Implement
Window Manager
Customizations

17.6. Specifying Click-to-Type
Focus

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17.6. Specifying Click-to-Type Focus
Most versions of fvwm2 are configured to use the pointer focus model (FocusFollowsMouse or MouseFocus in
the configuration file). This means you need to move the pointer into a window in order to type in it, post an
application menu, and so forth. However, fvwm2 is somewhat more versatile than other window managers in
this regard.

There are two other focus policies available: click-to-type focus (ClickToFocus), which requires you to click
the pointer on the window in order to type in it, and the very handy SloppyFocus, which is like pointer focus
with a twist --the focus does not leave the last window that had it until you move it into another window that
takes over the focus. This can come in handy, particularly with terminal emulator windows like xterm and
rxvt. You can actually move the pointer out of the way --accidentally or on purpose --and still continue to
type in the window.

The best part of fvwm2's way of handling focus policy is that you can mix and match what windows use what
type of focus. All of the settings for focus policy are used as arguments to the Style variable. (Style takes
several arguments that determine the appearance and behavior of a particular client or window manager
component.)

In the following excerpt from a configuration file, the first line makes pointer focus the default for all
applications (the asterisk is a wildcard). The subsequent lines specify the exceptions to this rule. The button bar
works better with click-to-type focus, as do xman (the manpage viewer) and xmag (a magnification tool). The
two terminal emulators benefit from sloppy focus.

Style "*" FocusFollowsMouse Style "FvwmButtons" Icon toolbox. xpm, ClickToFocus Style "xman" Icon xman. xpm, RandomPlacement, ClickToFocus Style "xmag" Icon mag_ glass. xpm, RandomPlacement, ClickToFocus Style "XTerm" Icon xterm. xpm, SloppyFocus, IconBox -70 1 -1 -140 Style "rxvt" Icon term. xpm, SloppyFocus, IconBox -70 1 -1 -140

(See Style on the fvwm2 manpage for more information about this versatile option.)
In our sample configuration, the Simple Config Ops submenu of the Root menu offers three items that let you
change the focus policy on the fly, just for the current window manager session:

l Sloppy Focus

l Click to Focus
l Focus Follows Mouse

Note, however, that these items supersede what's in your configuration file for all applications. If you want to
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recover the more specialized definitions in your configuration file, you'll have to restart the window manager.

17.5. A Quick Tour of the
fvwm Environment
17.7. Raising the Focus
Window Automatically

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17.7. Raising the Focus Window Automatically
If you're using pointer focus (FocusFollowsMouse), you might want to consider also using the
FvwmAuto module to automatically raise the focus window. If we add the following line to
our .fvwm2rc file, the focus window is automatically raised after the pointer has been in it for
200 milliseconds:

Module FvwmAuto 200(That's one-fifth of a second to metric-resistant types.) The delay is important and makes
FvwmAuto much more practical. Generally when pointer focus is in effect, an autoraise
feature can make the display seem chaotic: when you move the pointer across the screen, the
focus hits several windows and they are raised in a distracting shuffle. With an autoraise
delay, you can avoid the shuffling by moving the pointer quickly to the window you want to
focus on.

If you use ClickToFocus mode by default, the autoraise feature is built in and you don't have
to make this modification.

Of course, those who adapt to using the FvwmWinList module to transfer focus will have
their windows raised automatically, without having to edit their .fvwm2rc file --or even move
the pointer off the WinList.

One of your menus may also be configured to offer an item that turns on autoraise on the fly
and another item that turns it off again. In some default setups, the Fvwm Modules menu
features AutoRaise and Stop AutoRaise for these purposes.

17.6. Specifying Click-to-Type
Focus
17.8. Changing the Size of
the Desktop

Copyright © 2001 O'Reilly & QKFIN. All rights reserved.
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17.8. Changing the Size of the Desktop
Many default configuration files have a default desktop of two screen pages across
(horizontal) by two screen pages down (vertical), which in the configuration file is defined
using the line:

DeskTopSize 2x2It's easy to change the size of your desktop by editing the dimensions of the grid. Thus, the
following line creates a desktop of three pages across by two pages down:

DeskTopSize 3x2You don't have to have multiple pages in both directions. You can have a desktop of one page
above another above another:

DeskTopSize 1x3You don't even have to have multiple pages at all:
DeskTopSize 1x1But then why use fvwm2?
Of course, the number of pages you select will depend on your space needs and style of
working and also on whether you will use more than one desktop (described in the next
section). If you configure for multiple desktops, each one will have the same exact
DeskTopSize. So if you want a desktop for work and one for play, you may not need each one
to be many pages. Two desktops of three-by-three, for instance, would give you a total of 18
pages to get lost on. Yipes. However, graphical artists may welcome a larger workspace.

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17.7. Raising the Focus
Window Automatically
17.9. Having Multiple
Desktops

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17.9. Having Multiple Desktops
In order to work with multiple desktops, you simply have to configure the Pager to display the number of desktops you want. Each
desktop will have the same number of pages, the number you've specified using DeskTopSize (see Section 17.8, "Changing the Size

of the Desktop").

In order to specify more than one desktop, you'll need to edit a line that looks something like this one:
*FvwmButtons( 2x2 Frame 2 Swallow( UseOld) "FvwmPager" "Module FvwmPager 0 0")This line incorporates the Pager into the FvwmButtons module (the button bar). The two numbers at the end of the definition line give
the range of desktops visible. The first desktop is number 0, and in this case the last desktop is also number 0 --i. e., there is only one.

If you want two desktops, change the final number to a 1:
*FvwmButtons( 1x2 Frame 2 Swallow( UseOld) "FvwmPager" "Module FvwmPager 0 1")The following line would create a Pager with four desktops, numbered through 3:
*FvwmButtons( 1x2 Frame 2 Swallow( UseOld) "FvwmPager" "Module FvwmPager 0 3")Few people will require this much space. But even if you add only a single desktop, keep in mind that you may have to change the
overall dimensions of the Pager, and thus of the button bar that contains it, in order to have a reasonably sized view of your various
desktops. You may also have to reallocate the space you have so that the Pager gets a large enough area.

There are a few relevant sizes you can tinker with to make room for a Pager that shows multiple desktops:
l The dimensions of the button bar (FvwmButtons module)
l The number of columns the button bar is divided into
l How many of those columns the Pager takes up

A typical FvwmButtons module might be 520 pixels wide and 100 pixels high:
*FvwmButtonsGeometry 520x100-1-1And it might be configured as two rows and five columns (the sizes of which are entirely dependent on FvwmButton's geometry):
*FvwmButtons( Frame 2 Padding 2 2 Container( Rows 2 Columns 5 Frame 1 Padding 10 0))In this particular setup, the Pager takes up a one-column by two-row section of the FvwmButtons module:
*FvwmButtons( 1x2 Frame 2 Swallow( UseOld) "FvwmPager" "Module FvwmPager 0 1")The Icon Manager takes up three columns:
*FvwmButtons( 3x2 Frame 2 Swallow "FvwmIconMan" "Module FvwmIconMan")And the remaining column is occupied by the desktop applications (e. g., xbiff, xclock, xload) that run within a Container in the
FvwmButtons module:

*FvwmButtons( 1x2 Frame 0 Container( Rows 2 Columns 2 Frame 0))

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*FvwmButtons( Frame 2 Swallow( UseOld, NoHints, Respawn) "xbiff" 'Exec exec xbiff -bg bisque3') *FvwmButtons( Frame 3 Swallow( UseOld, NoHints, Respawn) "xclock" 'Exec exec xclock -bg bisque3 -fg black -hd black -hl black -padding 0 update 1') *FvwmButtons( 2x1 Frame 2 Swallow( UseOld, NoHints, Respawn) "xload" 'Exec exec xload -bg bisque3 -fg black -update 5 -nolabel')

Notice that the container is further subdivided into two rows and two columns so the applications can be laid out. But don't let this
layer confuse you. (Parsing the configuration file can be exacting.)

Back to the issue of multiple desktops. If you want two desktops, first set that up by changing the number of the final desktop to a 1 at
the end of this line:

*FvwmButtons( 1x2 Frame 2 Swallow( UseOld) "FvwmPager" "Module FvwmPager 0 1")Then to make the Pager big enough to display both desktops adequately, add some pixels to the width of the button bar. Here's an
extra hundred from the 520 we started with:

*FvwmButtonsGeometry 620x100-1-1And let's also reallocate the available five columns so that the icon manager takes up only two (rather than the three it started with),
and give the extra column to the Pager. The section with the applications remains a single column wide:

*FvwmButtons( 2x2 Frame 2 Swallow "FvwmIconMan" "Module FvwmIconMan") *FvwmButtons( 2x2 Frame 2 Swallow( UseOld) "FvwmPager" "Module FvwmPager 0 0") *FvwmButtons( 1x2 Frame 0 Container( Rows 2 Columns 2 Frame 0))

Figure 17-2 shows our new double desktop reflected in the updated button box. This is just one sample customization. With your
individual needs and display specifics, you can imagine how complicated this can get. But it's easy to test your changes by simply
restarting the window manager.

Figure 17-2. The modified FvwmButtons module shows two desktops in the Pager
17.8. Changing the Size of
the Desktop
17.10. Making the Same
Window Appear on Every
Page

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17.10. Making the Same Window Appear on Every Page
A window that appears on every virtual screen page is called a sticky window because it seems to stick to the glass.
Some windows are designated as sticky in the system. fvwm2rc file, among them xbiff, programs ending in lock (e. g.,
clock programs such as xclock and oclock), and all of the fvwm2 modules (because you need the button bar, Pager, etc.,
on every page).

If you want a window to appear on the desktop no matter what page you're viewing, you need to specify that in your
.fvwm2rc file. The specification requires you to use the Style variable, followed by the client's name, and a hard-to-forget
parameter, Sticky. The Style variable is used to set many different characteristics. Here are some lines you might
see in a configuration file to establish that a window is sticky, among other things:

Style "xbiff" NoTitle, Sticky, WindowListSkip, ClickToFocus Style "* lock" NoTitle, NoHandles, Sticky, WindowListSkip, ClickToFocus Style "Fvwm*" NoTitle, Sticky, WindowListSkip

Notice that the Style variable can recognize a wildcard character (*) to widen the scope of the definition. Fvwm* would
encompass all fvwm2 modules.

Try adding the following line, which specifies that an application called xpostit will stick to the glass:
Style "xpostit" StickyPractically speaking, you probably also want to specify that xpostit uses click-to-type focus and doesn't appear on the
FvwmWinList, so this definition is better:

Style "xpostit" Sticky, WindowListSkip, ClickToFocusIn most cases, you'll want only small windows that you run a single instance of (and that you use frequently) to be
sticky. Having a terminal emulator like xterm appear on every page is not as practical; it would take up too much space.
However, if you do want a client like xterm to follow you around, be sure to give that instance of the program a
distinctive name using the -name option.

For example, in your X session startup file you could run an xterm you name mailwindow:
xterm -name mailwindow &Then make that window appear on every page by adding the following line to your .fvwm2rc file:
Style "mailwindow" StickyIf you'd like to make a particular window sticky temporarily, look for an Fvwm Window Ops menu under your Root
menu. Commonly you will find a toggle to (Un) Stick a Window. Or you can set up such a menu item yourself. See
Section 17.14, "Customizing Menus", later in this chapter.

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17.9. Having Multiple
Desktops
17.11. Starting Windows on
Different Desktops and Pages

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17.11. Starting Windows on Different
Desktops and Pages

There's an obvious, low-tech way to start applications on different desktops and on different
pages within a desktop: switch the view to the desktop and page you want (using the Pager,
keyboard shortcuts, or whatever method you like), open a terminal emulator window (e. g.,
using the Root menu), then run any program you like. Voila. The application window opens
on the current desktop and page.

But there are two automated ways to accomplish this same thing. In the first method, you
specify in your .fvwm2rc file that certain programs will appear on certain desktops and/ or
pages automatically when you run them. You do this using fvwm2's Style variable, which
takes two relevant options: StartsOnPage and StartsOnDesk.

Here comes a confusing part. StartsOnPage takes up to three numeric arguments. If there is
only one argument, it corresponds to the number of the desk on which to open the application.
If there are three arguments, the second and third additionally identify the page, using an X, Y
coordinate scheme. We'll come back to this in a moment. (Two arguments alone are
interpreted as the X, Y coordinates of the page.)

And what about the closely associated StartsOnDesk variable? A little more confusion here.
StartsOnDesk takes only one argument: the desk number. But since you can set this with
StartsOnPage, along with the more specific page address, in practice there is no need to use
StartsOnDesk at all. The only real reason to use StartsOnDesk is if you want your .fvwm2rc
file definitions to be as obvious as possible.

Now back to desktop and page addressing. Let's consider the addressing scheme of a single
two-by-two-page desktop. Just as the first desk is addressed as number 0, the first page on a
desk is 0,0. The next page to the right is 1,0. The third page clockwise (the lower-right
quadrant) is 1,1. And the fourth page clockwise (the lower-left quadrant) is 0,1.

Supposing there are at least two desktops of four pages each, the following definition says that
when you run an xterm called "bigxterm" it will be opened in the lower-left quadrant (0,1) of
the second desktop (number 1):

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Style "bigxterm" StartsOnPage 1 0 1

Once you make this update to your .fvwm2rc file and restart the window manager, running the
command:

xterm -name bigxterm &will open the window where you want it.
You also have the option of accomplishing the same thing using X resource syntax on the
command line. This strategy may even be a little more practical than putting the definitions in
your .fvwm2rc file because you won't have to define many different instances of the various
programs (e. g., bigxterm, littlexterm, mailwindow, or whatever). The -xrm option (recognized
by many X clients) lets you specify an X resource variable on the command line:

xterm -xrm '* Page: 1 0 1' &You can even put a series of such lines in your X session startup file in order to open
applications wherever you want them on your desktop( s) when you log in.

While it looks as if these two methods of opening windows on different desktops/ pages (the
Style variable with StartsOnPage or StartsOnDesk and the -xrm command-line option)
produce identical results, there is actually a subtle difference in behavior. When you use Style
with StartsOnPage (or StartsOnDesk) and you specify only the desktop number, the window
is opened on the first page (0,0) of that desk. If you give the same information on the
command line (using -xrm), the destination page of the new window is related to the page
you're on when you run the command. The new window appears on the analogous page of the
desktop you specify.

You have still one more alternative if you're interested in opening a window on a different
page within the current desktop. Run a window with the -geometry option and supply large
enough coordinates to place it on a particular page in the desktop. If you use a desktop three
pages square, the following line places a window in the middle page (of the nine-page grid):

xterm -geometry +1200+ 1200 &Keep in mind, however, that display-specific characteristics play a big part in gauging these
distances, and they are not easy to guess.

17.10. Making the Same
Window Appear on Every
Page

17.12. If It's Too Hard (or
Easy) to Move the Pointer
Between Pages

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17.12. If It's Too Hard (or Easy) to Move the
Pointer Between Pages

If you're trying to navigate the desktop by moving the pointer and you find it either too easy
or too difficult to go from one page to the next, there's a configuration file variable you can
customize. The aptly named EdgeResistance variable lets you adjust how easy it is to move
the pointer beyond the perimeter of the current page.

The variable takes two parameters. The first is more relevant to the problem at hand: the
number of milliseconds the pointer must be at the screen edge before you'll be moved onto the
next page. The second parameter has to do with the way a window is moved between pages:
it's the number of pixels over the edge of the screen a window's border must move before it
moves partially off the screen. Typical default settings are:

EdgeResistance 250 10Some people find the EdgeResistance they're working with is too low for them, the
inconvenient result being that they inadvertently knock the pointer off of the current screen
page. If this is your problem, you can increase the first parameter:

EdgeResistance 500 10A first parameter between 500 and 1000 will greatly enhance the resistance. The maximum
resistance is 10000, which actually makes it impossible to page over.

As it happens, if you have the opposite problem and have to bounce the mouse against what
feels like a hard rubber wall in order to page over, try reducing the first number:

EdgeResistance 100 10In a typical default configuration, fvwm2 is set up to provide a number of menu options that
let you change your paging options on the fly. A number of them are located on the Fvwm
Simple Config Ops menu, a submenu of the Root menu. Thus, you can toggle the ability to
page on and off with Full Paging On and All Paging Off.

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All Paging Off does exactly what it sounds like --it limits you to keeping the pointer on the
current page. You might prefer this if you're going to be working on that page for a while and
you don't want to worry about knocking the pointer onto another page. You can toggle paging
back on with the Full Paging On menu item.

There are other items to constrain paging in different ways (e. g., Horizontal Paging Only,
Vertical Paging Only).

The Partial Paging item lets you move the pointer so that the view straddles two adjacent
pages; the area you see will be highlighted in the Pager window.

The item Full Paging & Edge Wrap actually expands the range of paging possibilities.
Normally when you reach the edge of a desktop, you can't move the pointer beyond. With this
item selected, you can drag the pointer beyond the edge of the desktop, and it wraps around to
the page on the other side (either horizontally or vertically). Thus, if you have the pointer in
the upper-right page of a two-by-two desktop, and you drag the pointer off of the right edge, it
will wrap around to the upper-left page of that desktop.

Underlying all of these menu items is the EdgeScroll variable. Here are the EdgeScroll
parameters that map to the various menu items:

Full Paging ON EdgeScroll 100 100 All Paging OFF EdgeScroll 0 0 Horizontal Paging Only EdgeScroll 100 0 Vertical Paging Only EdgeScroll 0 100 Partial Paging EdgeScroll 50 50 Full Paging & Edge Wrap EdgeScroll 100000 100000

EdgeScroll's two parameters specify the percentage of a page to scroll when you reach the
border of the page. The first parameter is for horizontal moves, the second for vertical. If the
horizontal and vertical percentages are multipled by 1000, scrolling will wrap around at the
edge of the desktop. EdgeScroll 100000 100000 will wrap both for both horizontal
and vertical moves.

Rather than rely on menu items like these, you could make any of these a default behavior by
putting the EdgeScroll variable on its own line in your .fvwm2rc file. See the fvwm2 manpage
and check out the system. fvwm2rc file for guidance.

Note that none of these variations will scroll you from one desktop to another. The next
section shows how to configure some keyboard shortcuts to do just that.

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17.11. Starting Windows on
Different Desktops and Pages
17.13. Adding Keyboard
Shortcuts

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Linux in a Nutshell, 3rd
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17.13. Adding Keyboard Shortcuts
The bare-bones system. fvwmrc file that we started with offers little in the way of keyboard
shortcuts, or accelerators, for window management functions. But if you're one of those users who
prefers to keep her hands on the keyboard and off the mouse as much as possible, within your
.fvwm2rc file you can easily define keys to perform a variety of functions.

17.13.1. Keyboard Shortcuts to Navigate the Desktop
The Pager is a great tool for getting around one or more desktops. But many people hate using the
mouse. You can configure a bunch of keys to let you move around in various ways.

Add the following lines to your .fvwm2rc file to set up key combinations to scroll one page in any
direction on the desktop using Ctrl plus an arrow key. The view scrolls in the direction of the arrow.

Each definition uses the Key variable followed by:
1. The name of the key
2. The context (location) in which it must be typed
3. Any modifying keys (that must also be held down)
4. The action initiated by the key or key combination
Thus, in the following example, the first definition line says that pressing the left arrow key in any
"A" context, while also holding down the Ctrl "C" key will scroll the screen one page to the left on
the current desktop:

# Press arrow + Control in any context # to scroll by one page in the direction of the arrow Key Left A C Scroll -100 0 Key Right A C Scroll +100 +0 Key Up A C Scroll +0 -100 Key Down A C Scroll +0 +100

Table 17-1 summarizes the functionality.
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Table 17-1. Key Combinations to Change the Page
Key Combination Moves View

Control, right arrow key One page to the right
Control, left arrow key One page to the left
Control, up arrow key One page up
Control, down arrow key One page down

The Scroll variable takes the same parameters as EdgeScroll, which are explained in Section 17.12,
"If It's Too Hard (or Easy) to Move the Pointer Between Pages", earlier in this chapter. See the
fvwm2 manpage for more information. Note that the key combinations we've defined let you get
around a single desktop but won't let you advance to another desktop. We'll deal with that
contingency later.

Here's another possible key binding. This one advances the view to every page in the desktop in
order and finally wraps back to the first page. You use the Tab key while holding down Control,
again in any context. The definition line looks like this:

# Press Tab + Control in any context to scroll # by one page with wrap scrolling Key Tab A C Scroll 100000 0

Table 17-2 summarizes another page-changing combination.
Table 17-2. Another Key Combination to Change the Page

Key Combination Moves View

Control, Tab To the next page in the desktop
Since application windows can straddle pages, there may be times when you want the screen to
display a screenful other than a page proper. (You might also want to look at windows on two
different pages at once.) The following shortcuts scroll the view one-tenth of a page at a time.
Instead of Control, these shortcuts use the so-called Meta key. This is a symbolic name --the actual
key that serves the Meta function varies from keyboard to keyboard. In many cases, the key labeled
Alt serves as the Meta key. Here are the configuration file definition lines:

## Press arrow + meta key in any context ## to scroll by 1/ 10 of a page in the direction of arrow

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Key Left A M Scroll -10 +0 Key Right A M Scroll +10 +0 Key Up A M Scroll +0 -10 Key Down A M Scroll +0 +10

These lines establish the following functionality, outlined in Table 17-3.
Table 17-3. Key Combinations to Scroll the Page by 1/ 10

Key Combination Moves View

Meta, left arrow key One-tenth page to the left
Meta, right arrow key One-tenth page to the left
Meta, up arrow key One-tenth page up
Meta, down arrow key One-tenth page down

If you have more than one desktop, you can also create shortcuts to move between those. The
following two shortcuts are intended to let you go back and forth between desktops in a two-desktop
environment:

## Press Control + Return in any context ## to scroll forward by 1 desktop Key Return A C Desk 1 1 1 ## Press Shift + Control + Return in any context ## to scroll back by 1 desktop Key Return A SC Desk -1 0 0

Table 17-4 summarizes these shortcuts.
Table 17-4. Key Combinations to Scroll to the Next Desktop

Key Combination Moves View

Control + Return One desktop ahead
Shift + Control + Return One desktop back

The second and third parameters to the Desk variable constrain the paging so that you can't page
beyond the first or second desktops. (Hypothetically, you can page outside the view of the Pager!)
If you have more than two desktops, you will need to edit these definitions. See the fvwm2
manpage for more about the Desk variable.

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17.13.2. Moving the Pointer with Keystrokes

The previous section outlines some keyboard shortcuts you can define to scroll the page view. But
you can also define shortcuts to move the position of the pointer on the screen. Admittedly this is
for people who are downright mouse haters. But if you're someone who prefers to use the keyboard
to the mouse, these shortcuts can come in handy. They employ the CursorMove variable, also
described on the fvwm2 manpage.

The keyboard accelerators in the first group move the cursor symbol one-tenth of a screen at a time.
The first definition line says that pressing the left arrow key in any "A" context, while also holding
down the Shift "S" and Meta "M" keys will move the cursor one-tenth of a page in the direction of
the arrow:

## Press Shift + Meta + arrow in any context ## to move the pointer by 1/ 10 of a page in direction of arrow Key Left A SM CursorMove -10 +0 Key Right A SM CursorMove +10 +0 Key Up A SM CursorMove +0 -10 Key Down A SM CursorMove +0 +10

Table 17-5 summarizes the commands.
Table 17-5. Key Combinations to Move the Pointer by 1/ 10 of the Page

Key Combination Moves Pointer

Meta, Shift, left arrow key One-tenth of a page to the left
Meta, Shift, right arrow key One-tenth of a page to the right
Meta, Shift, up arrow key One-tenth of a page up
Meta, Shift, down arrow key One-tenth of a page down

If you want to have just about as much control moving the pointer with keystrokes as you do
moving it by hand, you can specify shortcuts to move it a mere one percent of a page at a time:

## Press Shift + Control + arrow in any context ## to move the pointer by 1% of a page in direction of arrow Key Left A SC CursorMove -1 0 Key Right A SC CursorMove +1 +0 Key Up A SC CursorMove +0 -1 Key Down A SC CursorMove +0 +1

Table 17-6 summarizes the commands.

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Table 17-6. Key Combinations to Move the Pointer by 1 Percent of the Page

Key Combination Moves Pointer

Shift, Control, left arrow key One percent of a page to the left
Shift, Control, right arrow key One percent of a page to the right
Shift, Control, up arrow key One percent of a page up
Shift, Control, down arrow key One percent of a page down

17.13.3. Keyboard Shortcuts for Menu and Window Manipulation
So far we've limited our keyboard shortcuts to scrolling the view and moving the pointer. But you
can create keyboard bindings for any window manager function.

Here are some sample bindings to perform simple window operations and to display a few menus:
# Keyboard accelerators Key F1 A M Iconify Key F2 A M Move Key F3 A M Resize Key F4 A M Popup "RootMenu" Key F5 A M Popup "Misc-Ops" Key F6 A M Popup "Utilities" Key F7 A M Popup "Module-Popup" Key F10 A M Restart fvwm2 Key F12 A SM Close

These are just sample bindings; you may want to set up your own keyboard shortcuts to do entirely
different things. But these bindings will let us look at some of the possibilities, as well as potential
problems.

In our sample definition lines, the first binding specifies that if you press the F1 function key while
holding down the Meta "M" key, with the pointer in any "A" context, the focus window will be
iconified (or deiconified). Meta+ F2 lets you initiate moving the focus window, while Meta+ F3
starts a resize operation. (The Meta key is described in the section "Keyboard Shortcuts to Navigate
the Desktop," earlier in this chapter.)

Note that if you've adopted the keyboard bindings to move the pointer (as described in the previous
section), you can perform the move and resize operations entirely with keystrokes. For example,
use Meta+ F2 to begin a move, then drag the window outline by moving the pointer symbol using
the appropriate keyboard shortcuts, then press the Return key to complete the operation.

In addition, we've set up function keys to pop-up four different menus, the contents of which are

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also defined in the .fvwm2rc file. Once a menu is popped up, you can use the up and down arrow
keys to highlight items on the menu, right and left keys to move down and up through submenus
(cascading menus), the Return key to select an item, and Esc to pop down the menu without making
a selection.

Because we do a lot of tinkering with fvwm2 customization, we have set up Meta+ F10 to restart
the window manager. This is much faster than bringing up menus.

We've also created a key combination to close the focus window: Shift+ Meta+ F12. Certainly it's
handy to be able to get rid of a window with a keyboard shortcut, but you don't want it to be too
easy or you may do it by mistake. Having an extra modifying key (Shift) and using the very last
function key (F12) require you to act deliberately in closing a window using this method.

17.12. If It's Too Hard (or
Easy) to Move the Pointer
Between Pages

17.14. Customizing Menus

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Edition

17.14. Customizing Menus
Among the window manager features and functions defined in the configuration file are the contents of
menus. The system. fvwm2rc file generally defines a number of menus intended to be useful to a large
percentage of people. But what menus you have, if any, and what they offer, are basically up to you.

Typically the Root menu would be defined:
AddToMenu RootMenu "Root Menu" Title + "XTerm" Exec exec xterm + "Rxvt" Exec exec rxvt + "" Nop + "Remote Logins" Popup Remote-Logins + "" Nop + "Utilities" Popup Utilities + "" Nop + "Fvwm Modules" Popup Module-Popup + "Fvwm Window Ops" Popup Window-Ops + "Fvwm Simple Config Ops" Popup Misc-Ops + "" Nop + "Refresh Screen" Refresh + "Recapture Screen" Recapture + "" Nop + "Exit Fvwm" Popup Quit-Verify

You use the AddToMenu variable to create a menu. The first parameter AddToMenu takes is the name of the
menu, in this case RootMenu. The menu name is used to reference the menu elsewhere in the configuration
file (e. g., to specify a key binding to pop-up the menu). (Note that the AddToMenu variable and the menu
name are repeated on each line of the menu definition, as indicated by the plus sign.

Each line of the definition creates a line on the menu; that may be the menu title, a menu item proper, a blank
line, or a separator. The third component of each line specifies the text that appears on that line. The fourth
component specifies the window manager function to be performed.

The first line of our example specifies the menu title. Lines with empty text fields ("") and the Nop function
(which specifies "No operation") are used to create divider lines on the menu.

The Pop-up function is worth looking at more closely. Pop-up specifies that a menu is displayed; the menu
name is given as an argument to Pop-up. When Pop-up is invoked from another menu, it creates a submenu
(or cascading menu). This sample Root Menu definition has six submenus, named Remote-Logins, Utilities,
Module-Popup, Window-Ops, Misc-Ops, and Quit-Verify. These menus would also be defined using the
AddToMenu command, elsewhere in the configuration file.

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You can use the sample menus in the system. fvwm2rc file and the fvwm2 manpage to modify the existing
menus or create your own. It is simple to replace definition lines in the template menus and not much more
difficult to write one from scratch.

You can also change how the menus are displayed. Perhaps you don't want a bunch of cascading menus off of
the Root menu. In the previous section we set up some function keys to display certain menus. That's one
option. You might instead specify pointer buttons to display various menus. In a typical default, the first
pointer button displays the Root menu and the second displays the Window Ops menu. But since most
Window Ops functions (e. g., Move, Resize, Iconify) are available using the pointer directly on parts of a
window, you may instead choose to have the second pointer button display another menu (e. g., Utilities).

17.13. Adding Keyboard
Shortcuts
17.15. The FvwmWinList:
Switching the Focus

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Linux in a Nutshell, 3rd
Edition

17.15. The FvwmWinList: Switching the Focus
The FvwmWinList is an fvwm2 module that lets you keep track of all the application windows on
your many screen pages. Generally the WinList is configured to let you switch the focus to whatever
window you want, but hypothetically you can set it up to perform other operations.

In many typical environments, you can start the FvwmWinList from an Fvwm Modules menu (often a
submenu of the Root menu). If you'd instead like to configure fvwm to start the WinList
automatically, see Section 17.15.2, "Making the FvwmWinList Part of Your Default Environment".

(You might also configure a keyboard shortcut to start the WinList module; see Section 17.13,
"Adding Keyboard Shortcuts " for details.)

Some of FvwmWinList's appearance and behavior can be customized. We'll see some typical module
definition lines in the next section. If you are using this configuration, FvwmWinList performs the
following operations:

First mouse button click:
Switch the focus to the window in question. If the window is iconified, deiconify. Switch the
screen view so that the page with the window is displayed.
Second mouse button click:

Iconify/ deiconify window; the page displayed does not change.
Third mouse button click:

Display a pop-up box containing information about the window in question (e. g., dimensions in
pixels, whether it is sticky, permanent or transient, etc.). Pop down the box by clicking any
mouse button on it.

One of the interesting features of the WinList is that none of these commands moves the pointer to the
focus window. Instead, the pointer stays on the entry in the WinList that corresponds to the focus
window.

Hypothetically you could simply keep the pointer on the FvwmWinList and do all of your navigation
from there --except when you want to work with the FvwmButtons module or another of the windows
that don't normally appear in the WinList.

17.15.1. Using the FvwmWinList with Multiple Instances of the
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Same Window

The primary limitation of the FvwmWinList is that it's somewhat difficult to tell which window in the
list is which. Each entry in the FvwmWinList gives the text that appears in the corresponding
window's titlebar. (If the titlebar is suppressed, it gives the text that would normally appear.) If you
tend to run the same program many times simultaneously --e. g., several xterms --on the
FvwmWinList, they all look alike. (The one difference is that iconified windows have entries
surrounded by parentheses.)

If you get attached to using the FvwmWinList, you should probably specify different titles for multiple
instances of the same window. The standard X options -title or -name will do the trick. Note,
however, that while -title changes only the text in the titlebar, -name literally changes the name of the
application. Thus it affects how resources and configuration file parameters are assigned.

17.15.2. Making the FvwmWinList Part of Your Default Environment
If you want to make FvwmWinList part of your default environment, edit your configuration file to
have it run at both initialization and restart of the window manager. In the following example, we've
added lines three and six for these purposes:

AddToFunc InitFunction "I" Module FvwmButtons + "I" exec xsetroot -mod 2 2 -fg \# 554055 -bg \# 705070 + "I" Module FvwmWinList

AddToFunc RestartFunction "I" Module FvwmButtons + "I" exec xsetroot -mod 2 2 -fg \# 554055 -bg \# 705070 + "I" Module FvwmWinList

These lines specify that the FvwmWinList module is run whenever you start or restart the window
manager. The window appears in the bottom left corner of the screen.

As an alternative, you might make the FvwmWinList appear as a pop-up menu. The following
definition binds the module to the third pointer button when it is held down on the root window (this
may not be as handy as having the module present all the time):

Mouse 3 R A Module FvwmWinList TransientBut running a module is different than specifying how it looks and behaves. Like a number of other
modules (FvwmButtonBox, FvwmPager, etc.), the various characteristics of the FvwmWinList are
defined elsewhere in the configuration file. Here are some typical definition lines:

######################### FvwmWinList######################### *FvwmWinListBack #908090 *FvwmWinListFore Black *FvwmWinListFont -adobe-helvetica-bold-r-*-*-10-*-*-*-*-*-*-* *FvwmWinListAction Click1 Iconify -1, Focus *FvwmWinListAction Click2 Iconify *FvwmWinListAction Click3 Module "FvwmIdent" FvwmIdent

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*FvwmWinListUseSkipList *FvwmWinListGeometry +0-1

The first three lines specify the background color, foreground color, and text font used for the
application. The next three define what actions first, second, and third mouse button clicks invoke
when you do them within the WinList. UseSkipList tells the WinList not to list any windows that are
assigned the Style classification WindowListSkip elsewhere in the configuration file. (Generally all
module windows are classified thus and will not appear in the FvwmWinList.) The final line specifies
the location at which the window should appear (bottom-left corner).

The WinList is also a sticky window; that is, it appears on every page on every desktop. But the
configuration file can be confusing. This characteristic is specified elsewhere in the file, using the
Style option:

Style "Fvwm*" NoTitle, Sticky, WindowListSkipThis line specifies that all modules (including the WinList) have no titlebars, are sticky, and will not
appear on the FvwmWinList. In the case of the FvwmWinList module, having it appear as an entry on
itself would be more than a little confusing.

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Index: Linux in a Nutshell (Linux in a Nutshell)
Index
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y
| Z

17. An Alternative Window
Manager: fvwm2
Colophon

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Index: 0 (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: 0
& command (ex): 11.13. Alphabetical Summary of ex Commands
< > command (ex): 11.13. Alphabetical Summary of ex Commands
* (asterisk) bash shell metacharacter: 7.3.2. Filename Metacharacters
\ (backslash) character escapes: 9.3. Metacharacters
! (bang)
bash shell metacharacter: 7.3.2. Filename Metacharacters

ex command: 11.13. Alphabetical Summary of ex Commands
^ (circumflex) pattern-matching metacharacter: 9.3. Metacharacters
: (colon)
bash shell command: 7.7. Built-in Commands

csh/ tcsh command: 8.9. Built-in csh and tcsh Commands
sed command: 12.5. Alphabetical Summary of sed Commands
$ (dollar sign) pattern-matching metacharacter: 9.3. Metacharacters
. (dot)
bash shell command: 7.7. Built-in Commands

pattern-matching metacharacter: 9.3. Metacharacters
= (equal sign)
ex command: 11.13. Alphabetical Summary of ex Commands

gawk assignment: 13.6. Variable and Array Assignments
sed command: 12.5. Alphabetical Summary of sed Commands
# (hash mark)
bash shell command: 7.7. Built-in Commands

for comments: 12.5. Alphabetical Summary of sed Commands
csh/ tcsh command: 8.9. Built-in csh and tcsh Commands
#! command
bash shell command: 7.7. Built-in Commands

csh/ tcsh command: 8.9. Built-in csh and tcsh Commands
-(hyphen) pattern-matching metacharacter: 9.3. Metacharacters
+ (plus sign) pattern-matching metacharacter: 9.3. Metacharacters
? (question mark)
bash shell metacharacter: 7.3.2. Filename Metacharacters

pattern-matching metacharacter: 9.3. Metacharacters

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Index: 0 (Linux in a Nutshell)
~ (tilde) command (ex): 11.13. Alphabetical Summary of ex Commands
| pattern-matching metacharacter: 9.3. Metacharacters

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Index: A (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: A
a command (sed): 12.5. Alphabetical Summary of sed Commands
abbrev command (ex): 11.13. Alphabetical Summary of ex Commands
abbreviation commands, Emacs: 10.3.9. Word Abbreviation Commands
accelerators (see shortcuts)
access mode (see permissions, file)
ad| add commands (CVS): 14.4.7.1. add
addresses
IP: 2.3.1. IP Addresses

line, ex editor: 11.12.1. Options
pattern, sed editor: 12.3.1. Pattern Addressing
addsuffix variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
AddToMenu variable (fvwm2): 17.14. Customizing Menus
adm| admin commands (CVS)
-o option, use with caution: 14.3.8.1. admin

specifying ranges: 14.3.8.1. admin
adm| cdadmin commands (CVS): 14.3.8.1. admin
administrative files, CVS: 14.3.3. Repository Structure
variables: 14.3.3.1. The CVSROOT directory
agetty command: 3.1. Alphabetical Summary of Commands
alias command (bash): 7.7. Built-in Commands
alias command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
alias modules: 14.3.3.9. The modules file
aliases, special tcsh: 8.6.7. Special Aliases in tcsh
aligned panel, GNOME desktop: 15.2.1. Additional Panels
alignment, Emacs commands for: 10.3.14. Centering Commands
alloc command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
ampersand modules: 14.3.3.9. The modules file
animation settings
Enlightenment window manager: 15.4.9.5. Special FX

GNOME panel: 15.4.2.1. Animation
Sawfish window manager: 15.4.8.1. Appearance
ann| annotate commands (CVS): 14.4.7.2. annotate

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Index: A (Linux in a Nutshell)
apmd command: 3.1. Alphabetical Summary of Commands
apmd_ proxy command: 3.1. Alphabetical Summary of Commands
append command (ex): 11.13. Alphabetical Summary of ex Commands
applets
Desk Guide: 15.1. Desktop Overview

15.4.8.7. Workspaces
GNOME panel: 15.2. The Panel
Tasklist: 15.1. Desktop Overview
application launchers, adding to GNOME panel: 15.2.2. Adding an Application Launcher to
the Panel
applications
GNOME user interface for: 15.4.7.1. Applications

starting on different desktops (fvwm2): 17.11. Starting Windows on Different
Desktops and Pages
Applications modules, KDE: 16.3.1. Applications
apt-cdrom command (Debian): 5.2.5. Debian Package Manager Command Summary
apt-get command (Debian): 5.2. The Debian Package Manager
5.2.5. Debian Package Manager Command Summary
ar command: 3.1. Alphabetical Summary of Commands
arch command: 3.1. Alphabetical Summary of Commands
architecture type: 3.1. Alphabetical Summary of Commands
archive files: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
archives, CVS (see CVS utility, repositories)
args command (ex): 11.13. Alphabetical Summary of ex Commands
argv variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
arithmetic
bash arithmetic expressions: 7.5. Arithmetic Expressions

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$Author keyword (RCS): 14.8.1.1. Keywords
autocorrect variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
autoexpand variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
autolist variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
autologout variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
autoraising focus window, fvwm2: 17.7. Raising the Focus Window Automatically
awk program: 9.2. Metacharacters, Listed by Linux Program
9.4. Examples of Searching
13.1. Conceptual Overview
(see also gawk scripting language)

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Index: B (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: B
b command (sed): 12.5. Alphabetical Summary of sed Commands
background jobs: 7.7. Built-in Commands
8.8. Job Control
backslash (\) character escapes: 9.3. Metacharacters
backslash_ quote variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
Backspace key
bash and: 7.3.3. Command-line Editing

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Index: B (Linux in a Nutshell)
/bin/ echo command (see echo command)
bison command: 3.1. Alphabetical Summary of Commands
blocks, searching for bad: 3.1. Alphabetical Summary of Commands
blocksize, changing: 3.1. Alphabetical Summary of Commands
boot loaders: 4.1. The Boot Process
boot methods: 4. Boot Methods
boot parameters: 4.3. Loadlin: Booting from MS-DOS
4.5. Boot-time Kernel Options
boot sectors: 4.1. The Boot Process
bootpd command (TCP/ IP): 3.1. Alphabetical Summary of Commands
bootpgw command: 3.1. Alphabetical Summary of Commands
bootptest command (TCP/ IP): 3.1. Alphabetical Summary of Commands
border properties, KDE: 16.3.2.2. Borders
brackets (see [ ])
branches, revision control: 14.1.4. Branching
admin command and: 14.3.8.1. admin
log command and: 14.4.7.12. log
branching commands, sed: 12.4.5. Branching Commands
break command (bash): 7.7. Built-in Commands
break command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
break command (gawk): 13.8. Alphabetical Summary of Commands
breaking text lines: 3.1. Alphabetical Summary of Commands
breaksw command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
BSD (Berkeley Software Distribution): 1.3. Commands on Linux
1.5. Sources and Licenses
buffers
Emacs commands for: 10.3.10. Buffer Manipulation Commands

writing to disk: 3.1. Alphabetical Summary of Commands
built-in command (bash): 7.7. Built-in Commands
built-ins command (tcsh): 8.9. Built-in csh and tcsh Commands
bunzip2 command: 3.1. Alphabetical Summary of Commands
button bar, fvwm2: 17.5. A Quick Tour of the fvwm Environment
multiple desktops, specifying: 17.9. Having Multiple Desktops
button settings, GNOME panel: 15.4.2.2. Buttons
bye command (tcsh): 8.9. Built-in csh and tcsh Commands
bzcat command: 3.1. Alphabetical Summary of Commands
bzip2 command: 3.1. Alphabetical Summary of Commands
bzip2recover command: 3.1. Alphabetical Summary of Commands

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Index: B (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z

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Emacs commands for: 10.3.7. Capitalization Commands
case command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
cat command: 3.1. Alphabetical Summary of Commands
cc command (see gcc compiler)
cd command (bash): 7.7. Built-in Commands
cd command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
cd command (ex): 11.13. Alphabetical Summary of ex Commands
centering, Emacs commands for: 10.3.14. Centering Commands
cfdisk command: 3.1. Alphabetical Summary of Commands
chains (rule sets): 2.4. Overview of Firewalls and Masquerading
ipchains and: 3.1. Alphabetical Summary of Commands
iptables and: 3.1. Alphabetical Summary of Commands
change command (ex): 11.13. Alphabetical Summary of ex Commands
characters
counting in file: 3.1. Alphabetical Summary of Commands

keyboard repeat speed: 3.1. Alphabetical Summary of Commands
metacharacters (see metacharacters)

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Index: C (Linux in a Nutshell)
columns
deleting: 3.1. Alphabetical Summary of Commands

3.1. Alphabetical Summary of Commands
formatting input into: 3.1. Alphabetical Summary of Commands
merging text lines into: 3.1. Alphabetical Summary of Commands
com| commit commands (CVS): 14.4.7.4. commit
comm command: 3.1. Alphabetical Summary of Commands
command command (bash): 7.7. Built-in Commands
command history (see history, command)
command line
ex editor options: 11.3. ex Command-Line Options

gawk language syntax: 13.2. Command-Line Syntax
processing arguments on: 7.7. Built-in Commands
sed editor syntax: 12.2. Command-Line Syntax
vi editor options: 11.2. vi Command-Line Options
command-line editing
bash commands for: 7.3.3. Command-line Editing

csh/ tcsh commands for: 8.7.5. Command-Line Editing with tcsh
command mode (vi): 11.1.1. Command Mode
list of keys: 11.11. Alphabetical List of Keys in Command Mode
command substitution (csh/ tcsh): 8.6.1. Command Substitution
command variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
commands
aliases for: 7.7. Built-in Commands

bash shell: 7.3.5. Command Forms
7.7. Built-in Commands
completion (see completion)
csh and tcsh: 8.3.4. Command Forms
8.9. Built-in csh and tcsh Commands
CVS administrator: 14.3.8. Administrator Commands
CVS user: 14.4.7. User Commands
Debian Package Manager: 5.2.5. Debian Package Manager Command Summary
Emacs: 10.2.3. Absolutely Essential Commands
ex editor: 11.12. Syntax of ex Commands
executing
after hangup: 3.1. Alphabetical Summary of Commands

from standard input: 3.1. Alphabetical Summary of Commands
on remote hosts: 3.1. Alphabetical Summary of Commands
FTP: 3.1. Alphabetical Summary of Commands
gawk language: 13.7. Group Listing of gawk Commands
gdb (GNU debugger): 3.1. Alphabetical Summary of Commands
Linux: 1.3. Commands on Linux

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csh/ tcsh commands for: 8.7.1. Completion
comp. os. linux. admin: 0.1.3. LinuxUsenet Newsgroups
comp. os. linux. announce: 0.1.3. LinuxUsenet Newsgroups
comp. os. linux. development: 0.1.3. LinuxUsenet Newsgroups
comp. os. linux. help: 0.1.3. LinuxUsenet Newsgroups
comp. os. linux. misc: 0.1.3. LinuxUsenet Newsgroups
comp. os. linux. networking: 0.1.3. LinuxUsenet Newsgroups
compress command: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
compression, file
bzip2 command: 3.1. Alphabetical Summary of Commands

changing .Z files to .gz: 3.1. Alphabetical Summary of Commands
compress command: 3.1. Alphabetical Summary of Commands

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Index: C (Linux in a Nutshell)
6.4. Differing Features
8. csh and tcsh
sample .cshrc file: 8.4.5. Sample .cshrc File
csplit command: 3.1. Alphabetical Summary of Commands
ctags command: 3.1. Alphabetical Summary of Commands
current
time and date: 3.1. Alphabetical Summary of Commands

working directory: 3.1. Alphabetical Summary of Commands
cursor movement
Emacs commands for: 10.3.2. Cursor Movement Commands

vi commands for: 11.4. Movement Commands
CursorMove variable (fvwm2): 17.13.2. Moving the Pointer with Keystrokes
customizing Linux session: 6.1.2. Customization of Your Linux Session
cut command: 3.1. Alphabetical Summary of Commands
cutting (see yanking and pasting)
CVS utility: 1.4. What This Book Offers
14. CVS and RCS
administrator commands: 14.3.8. Administrator Commands
administrator reference: 14.3. CVS Administrator Reference
basic concepts: 14.1. Basic Concepts
branches/ forks: 14.1.4. Branching
client configuration files: 14.4.2. Configuring CVS
client options, common: 14.4.6. Common Client Options
command format: 14.2. The CVS Utility
confusing aspects of: 14.2.3. Gotchas
date formats: 14.4.6.1. Date formats
environment variables: 14.4.2. Configuring CVS
global options
client: 14.4.5. Client Global Options

common: 14.2.2. Common Global Options
server: 14.3.7. Global Server Option
importing
code snapshots: 14.3.5.1. Importing code snapshots

entire projects: 14.3.4.2. Bulk importing
from PVCS: 14.3.5.4. Importing from PVCS
from RCS: 14.3.5.2. Importing from RCS
from SCCS: 14.3.5.3. Importing from SCCS
keyword substitutions: 14.4.6.2. Keyword substitutions
locking model: 14.1.1. Locking and Merging
logical modules: 14.3.3.9. The modules file
merging model: 14.1.1. Locking and Merging
repositories: 14.1. Basic Concepts

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changing directories/ files: 14.3.4. Hacking the Repository
configuration information: 14.3.3.4. The config file
creating: 14.3.1. Creating a Repository
initializing: 14.3.8.2. init
notification of changes to: 14.3.3.8. The loginfo file
structure of: 14.3.3. Repository Structure
repository locators: 14.3.3.11. The passwd file
14.3.6. Using an Interim Shared Sandbox
14.4.1. Repository Locators
sandboxes: 14.1. Basic Concepts
creating: 14.4.3. Creating a Sandbox
directories/ files in: 14.4.4. Sandbox Structure
interim shared: 14.3.6. Using an Interim Shared Sandbox
release -d command, use with caution: 14.4.7.16. release
security issues: 14.3.2. Security Issues
specifying ranges: 14.3.8.1. admin
tracking files: 14.1.3. Tagging
user commands: 14.4.7. User Commands
user reference: 14.4. CVS User Reference
$CVS_ CLIENT_ LOG environment variable: 14.4.2. Configuring CVS
$CVS_ CLIENT_ PORT environment variable: 14.4.2. Configuring CVS
$CVSEDITOR environment variable: 14.4.2. Configuring CVS
cvsignore administrative file: 14.3.3.5. The cvsignore file
.cvsignore configuration file: 14.4.2. Configuring CVS
$CVSIGNORE environment variable: 14.4.2. Configuring CVS
$CVS_ IGNORE_ REMOTE_ ROOT environment variable: 14.4.2. Configuring CVS
.cvspass file: 14.4.2. Configuring CVS
$CVS_ PASSFILE environment variable: 14.4.2. Configuring CVS
.cvsrc file: 14.4.2. Configuring CVS
$CVS_ RCMD_ PORT environment variable: 14.4.2. Configuring CVS
$CVSREAD environment variable: 14.4.2. Configuring CVS
CVSROOT directory: 14.3.3.1. The CVSROOT directory
administrative files in: 14.3.3.1. The CVSROOT directory
$CVSROOT environment variable: 14.4.2. Configuring CVS
$CVS_ RSH environment variable: 14.4.2. Configuring CVS
$CVS_ SERVER environment variable: 14.4.2. Configuring CVS
$CVS_ SERVER_ SLEEP environment variable: 14.4.2. Configuring CVS
$CVSUMASK environment variable: 14.4.2. Configuring CVS
cvswrappers administrative file: 14.3.3.6. The cvswrappers file
.cvswrappers configuration file: 14.4.2. Configuring CVS
$CVSWRAPPERS environment variable: 14.4.2. Configuring CVS

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cwd variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
cyclic redundancy check (CRC): 3.1. Alphabetical Summary of Commands

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Index: D (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: D
d command (sed): 12.5. Alphabetical Summary of sed Commands
daemons: 2.2. Overview of Networking
commands for: 2.1.2. Daemons
NFS: 2.5.2. Daemons
routing: 2.3.2.2. Routing daemons
data transmission, verifying: 3.1. Alphabetical Summary of Commands
date (see time and date)
date command: 3.1. Alphabetical Summary of Commands
$Date keyword (RCS): 14.8.1.1. Keywords
dbm files: 3.1. Alphabetical Summary of Commands
dd command: 3.1. Alphabetical Summary of Commands
Debian Package Manager
commands: 5.2.5. Debian Package Manager Command Summary

files: 5.2.1. Files
package flags: 5.2.3. Package Flags
package/ selection states: 5.2.2. Package States and Selection States
packaging tools: 5.2. The Debian Package Manager
shell/ Perl scripts: 5.2.4. Scripts
debugfs command: 3.1. Alphabetical Summary of Commands
debugging
ext2 file system: 3.1. Alphabetical Summary of Commands

gdb (GNU debugger): 3.1. Alphabetical Summary of Commands
declare command (bash): 7.7. Built-in Commands
declaring variables/ arrays (gawk): 13.6. Variable and Array Assignments
default command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
Del key
bash and: 7.3.3. Command-line Editing

Emacs and: 10.2. Typical Problems
delete command (CVS) (see remove command (CVS))
delete command (ex): 11.13. Alphabetical Summary of ex Commands
delete command (gawk): 13.8. Alphabetical Summary of Commands
deleting

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GNOME settings: 15.4.1.1. Background
KDE settings: 16.3.2.1. Background
desktop customizations: 1.3. Commands on Linux
desktop environments
GNOME: 15. GNOME

KDE: 16. KDE
Desktop folder, KDE: 16.1.4. The Desktop Folder and kdelnk Files
desktop icons
adding to GNOME desktop: 15.1.1. Adding Desktop Icons

displaying on KDE desktop: 16.3.2.5. Desktop icons
movement/ placement on GNOME panel: 15.4.2.3. Panel objects
desktop links
adding applications to KDE panel: 16.2.3. Adding an Application Link to the Panel

adding to KDE desktop: 16.1.3. Adding a Link to the Desktop
configuring for KDE: 16.1.4. The Desktop Folder and kdelnk Files
setting colors for: 16.3.1.2. File manager
Desktop modules, KDE: 16.3.2. Desktop
desktop pager, KDE: 16.2.1. The Desktop Pager and Window List
desktop tools, fvwm2: 17.5. A Quick Tour of the fvwm Environment
desktops, multiple (fvwm2): 17.9. Having Multiple Desktops
/dev/ initrd file: 4.6. initrd: Using a RAM Disk
dextract variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
df command: 3.1. Alphabetical Summary of Commands
dialogs, GNOME user interface for: 15.4.7.2. Dialogs
dictionary, spelling: 3.1. Alphabetical Summary of Commands

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di| dif commands (CVS) (see diff command (CVS))
diff command: 3.1. Alphabetical Summary of Commands
diff command (CVS): 14.4.7.5. diff
dip command: 3.1. Alphabetical Summary of Commands
dir variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
directives, cpp: 3.1. Alphabetical Summary of Commands
directories
changing: 7.7. Built-in Commands

copying archives to: 3.1. Alphabetical Summary of Commands
formatting: 3.1. Alphabetical Summary of Commands
parameters: 3.1. Alphabetical Summary of Commands
4.2.1.1. Global options
partitioning: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
space on (see memory)
usage information for: 3.1. Alphabetical Summary of Commands
writing filesystem buffers to: 3.1. Alphabetical Summary of Commands
disown command (bash): 7.7. Built-in Commands
display (see terminals)
displaying
escape sequences: 3.1. Alphabetical Summary of Commands

reverse linefeeds: 3.1. Alphabetical Summary of Commands
distributing software, package for: 3.1. Alphabetical Summary of Commands

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distribution of Linux: 1.5. Sources and Licenses
dmesg command: 3.1. Alphabetical Summary of Commands
DNS (Domain Name System): 2.3.3. Name Service
dnsdomainname command (TCP/ IP): 3.1. Alphabetical Summary of Commands
do command (gawk): 13.8. Alphabetical Summary of Commands
documentation: 0.1.1. Online Documentation
Emacs: 10.3.16. Detail Information Help Commands
info files: 3.1. Alphabetical Summary of Commands
man pages: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
TCP/ IP: 2.3. Overview of TCP/ IP
dollar sign ($) pattern-matching metacharacter: 9.3. Metacharacters
domainname command (NFS/ NIS): 3.1. Alphabetical Summary of Commands
domains: 2.6.2. Domains
dosfsck command: 3.1. Alphabetical Summary of Commands
dpkg command (Debian): 5.2. The Debian Package Manager
5.2.5. Debian Package Manager Command Summary
dpkg-deb command (Debian): 5.2. The Debian Package Manager
5.2.5. Debian Package Manager Command Summary
dpkg-split command (Debian): 5.2.5. Debian Package Manager Command Summary
DPMS (Display Power Management System), KDE: 16.3.2.6. DPMS
dselect command (Debian): 5.2. The Debian Package Manager
5.2.5. Debian Package Manager Command Summary
dspmbyte variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
du command: 3.1. Alphabetical Summary of Commands
dual booting
Linux and Windows 95/ 98: 4.2. LILO: The Linux Loader

Linux and Windows NT/ 2001: 4.4. Dual Booting Linux and Windows NT/ 2001
dumpe2fs command: 3.1. Alphabetical Summary of Commands
dumpkeys command: 3.1. Alphabetical Summary of Commands
dunique variable (csh/ tcsh): 8.4.3. Predefined Shell Variables

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Index: E (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: E
echo command: 3.1. Alphabetical Summary of Commands
echo command (bash): 7.7. Built-in Commands
echo command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
echo variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
echo_ style variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
echotc command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
ed editor: 9.2. Metacharacters, Listed by Linux Program
9.4. Examples of Searching
edge panel, GNOME desktop: 15.2.1. Additional Panels
EdgeResistance variable (fvwm2): 17.12. If It's Too Hard (or Easy) to Move the Pointer
Between Pages
EdgeScroll variable (fvwm2): 17.12. If It's Too Hard (or Easy) to Move the Pointer Between
Pages
edit command (CVS): 14.4.7.6. edit
edit command (ex): 11.13. Alphabetical Summary of ex Commands
editing
on command line: 12.4.1. Basic Editing

on command line:: command line: 8.7.5. Command-Line Editing with tcsh
vi commands for: 11.5. Edit Commands
$EDITOR environment variable (CVS): 14.4.2. Configuring CVS
editor, GNOME default: 15.4.3.1. Default editor
editors command (CVS): 14.4.7.7. editors
e2fsck command: 3.1. Alphabetical Summary of Commands
egrep command: 3.1. Alphabetical Summary of Commands
9.4. Examples of Searching
metacharacters for: 9.2. Metacharacters, Listed by Linux Program
electronic mail (see mail)
ellipsis variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
Emacs editor: 1.4. What This Book Offers
3.1. Alphabetical Summary of Commands
10.1. Introduction

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Emacs mode (csh/ tcsh): 8.7.5.1. Emacs mode
Emacs-style commands: 7.3.3. Command-line Editing
email messages
automatic replies to: 3.1. Alphabetical Summary of Commands

encoding binary files for: 3.1. Alphabetical Summary of Commands
encoded files, recreating original file: 3.1. Alphabetical Summary of Commands
Enlightenment window manager
desktop components, moving: 15.4.9.5. Special FX

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e2fsck command and: 3.1. Alphabetical Summary of Commands
formatting device as: 3.1. Alphabetical Summary of Commands
tuning the parameters of: 3.1. Alphabetical Summary of Commands
external repository locator: 14.4.1. Repository Locators
exusage command (ex): 11.13. Alphabetical Summary of ex Commands

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archive (see archive files)
attributes: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
for bash shell: 7.3.1. Special Files
binary, converting for email: 3.1. Alphabetical Summary of Commands
calculating checksum for: 3.1. Alphabetical Summary of Commands
checking: 3.1. Alphabetical Summary of Commands

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Index: F (Linux in a Nutshell)
3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
pseudonyms for (see symbolic links)
removing duplicate lines from: 3.1. Alphabetical Summary of Commands
renaming: 3.1. Alphabetical Summary of Commands
revision control
CVS utility: 14. CVS and RCS

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fvwm2: 17.6. Specifying Click-to-Type Focus
KDE: 16.3.7.4. Properties
Sawfish window manager: 15.4.8.2. Focus behavior
FocusFollowsMouse policy (fvwm2): 17.6. Specifying Click-to-Type Focus
fold command: 3.1. Alphabetical Summary of Commands
font settings, KDE: 16.3.2.4. Fonts
foot menu, GNOME: 15.3. The Main Menu
for command (gawk): 13.8. Alphabetical Summary of Commands
for loops: 7.7. Built-in Commands
foreach command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
foreground jobs: 7.7. Built-in Commands
8.8. Job Control
forks, revision control: 14.1.4. Branching
formail command: 3.1. Alphabetical Summary of Commands
format
disk: 3.1. Alphabetical Summary of Commands

files as pages: 3.1. Alphabetical Summary of Commands
mailbox, filtering stdin into: 3.1. Alphabetical Summary of Commands
tcsh prompt: 8.4.4. Formatting for the Prompt Variable
time and date: 3.1. Alphabetical Summary of Commands
free command: 3.1. Alphabetical Summary of Commands
Free Software Foundation (FSF): 1.3. Commands on Linux

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Index: F (Linux in a Nutshell)
1.5. Sources and Licenses
freeze command (CVS) (see ta| tag commands (CVS))
fsck command: 3.1. Alphabetical Summary of Commands
fsck. ext2 command: 3.1. Alphabetical Summary of Commands
fsck. minix command: 3.1. Alphabetical Summary of Commands
ftp command: 3.1. Alphabetical Summary of Commands
function command (gawk): 13.8. Alphabetical Summary of Commands
functions
bc language: 3.1. Alphabetical Summary of Commands

ctags command: 3.1. Alphabetical Summary of Commands
function bindings: 7.7. Built-in Commands
make utility: 3.1. Alphabetical Summary of Commands
fuser command: 3.1. Alphabetical Summary of Commands
fvwm2 window manager: 17. An Alternative Window Manager: fvwm2
AddToMenu variable: 17.14. Customizing Menus
autoraising focus window: 17.7. Raising the Focus Window Automatically
cascading menus: 17.5. A Quick Tour of the fvwm Environment
configuration files: 17.2. Configuration Files
CursorMove variable: 17.13.2. Moving the Pointer with Keystrokes
customizations
.fvwm2rc file and: 17.2. Configuration Files

implementing: 17.4. How to Implement Window Manager Customizations
Desk variable: 17.13.1. Keyboard Shortcuts to Navigate the Desktop
desktop size, changing: 17.8. Changing the Size of the Desktop
desktop tools: 17.5. A Quick Tour of the fvwm Environment
EdgeResistance Variable: 17.12. If It's Too Hard (or Easy) to Move the Pointer
Between Pages
EdgeScroll variable: 17.12. If It's Too Hard (or Easy) to Move the Pointer Between
Pages
focus policies
ClickToFocus: 17.6. Specifying Click-to-Type Focus

FocusFollowsMouse: 17.6. Specifying Click-to-Type Focus
SloppyFocus: 17.6. Specifying Click-to-Type Focus
grids: 17. An Alternative Window Manager: fvwm2
17.5. A Quick Tour of the fvwm Environment
17.8. Changing the Size of the Desktop
keyboard shortcuts: 17.13. Adding Keyboard Shortcuts
menus, customizing: 17.14. Customizing Menus
modules
FvwmAuto: 17.7. Raising the Focus Window Automatically

FvwmButtons: 17.5. A Quick Tour of the fvwm Environment
17.9. Having Multiple Desktops

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Index: F (Linux in a Nutshell)
FvwmIconMan: 17.5. A Quick Tour of the fvwm Environment
FvwmPager module: 17.3. A Modular Approach
FvwmWinList: 17.3. A Modular Approach
17.15. The FvwmWinList: Switching the Focus
Icon Manager: 17.5. A Quick Tour of the fvwm Environment
Pager: 17.3. A Modular Approach
17.9. Having Multiple Desktops
WinList: 17.3. A Modular Approach
17.15. The FvwmWinList: Switching the Focus
moving pointer with keystrokes: 17.13.2. Moving the Pointer with Keystrokes
moving the pointer easily: 17.12. If It's Too Hard (or Easy) to Move the Pointer
Between Pages
multiple desktops, specifying: 17.9. Having Multiple Desktops
paging options, changing: 17.12. If It's Too Hard (or Easy) to Move the Pointer
Between Pages
restarting: 17.4. How to Implement Window Manager Customizations
Root menu: 17.5. A Quick Tour of the fvwm Environment
customizing the: 17.14. Customizing Menus
Scroll variable: 17.13.1. Keyboard Shortcuts to Navigate the Desktop
starting applications on different desktops: 17.11. Starting Windows on Different
Desktops and Pages
Style variable
focus policies and: 17.6. Specifying Click-to-Type Focus

starting applications on different desktops: 17.11. Starting Windows on
Different Desktops and Pages
sticky windows and: 17.10. Making the Same Window Appear on Every Page
switching from GNOME or KDE to: 17.1. Running fvwm2
virtual screens: 17. An Alternative Window Manager: fvwm2
17.5. A Quick Tour of the fvwm Environment
FvwmAuto module: 17.7. Raising the Focus Window Automatically
FvwmButtons module: 17.5. A Quick Tour of the fvwm Environment
multiple desktops, specifying: 17.9. Having Multiple Desktops
FvwmIconMan module: 17.5. A Quick Tour of the fvwm Environment
FvwmPager module: 17.3. A Modular Approach
.fvwm2rc configuration file: 17.2. Configuration Files
autoraising focus window: 17.7. Raising the Focus Window Automatically
EdgeScroll variable and: 17.12. If It's Too Hard (or Easy) to Move the Pointer
Between Pages
keyboard shortcuts and: 17.13. Adding Keyboard Shortcuts
starting applications on different desktops: 17.11. Starting Windows on Different
Desktops and Pages

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Index: F (Linux in a Nutshell)
sticky windows and: 17.10. Making the Same Window Appear on Every Page
FvwmWinList module: 17.3. A Modular Approach
17.15. The FvwmWinList: Switching the Focus
making it part of default environment: 17.15.2. Making the FvwmWinList Part of Your
Default Environment

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Index: G (Linux in a Nutshell)
Animation tab: 15.4.2.1. Animation
Buttons tab: 15.4.2.2. Buttons
desktop settings: 15.4.1.1. Background
document handlers: 15.4.3. Document Handlers
keyboard settings: 15.4.5.1. Keyboard
Menu tab: 15.4.2.4. Menu
Miscellaneous tab: 15.4.2.5. Miscellaneous
mouse settings: 15.4.5.2. Mouse
multimedia settings: 15.4.4. Multimedia
Panel Objects tab: 15.4.2.3. Panel objects
panel settings: 15.4.2. Panel
startup programs: 15.4.6. Session
user interface settings: 15.4.7. User Interface
CORBA and: 15. GNOME
default editor: 15.4.3.1. Default editor
desktop customization: 15.4. The GNOME Control Center
desktop icons, adding: 15.1.1. Adding Desktop Icons
Enlightenment window manager (see Enlightenment window manager)
help files: 15.4.3.3. URL handlers
main menu: 15.3. The Main Menu
customizing the: 15.3. The Main Menu
menu editor: 15.3.2. Editing the Menu
panels
adding application launchers: 15.2.2. Adding an Application Launcher to the

Panel
configuring: 15.2.1. Additional Panels
15.4.2. Panel
creating new: 15.2.1. Additional Panels
settings for: 15.2. The Panel
Sawfish window manager (see Sawfish window manager)
screensavers: 15.4.1.2. Screensaver
shortcuts, adding: 15.1.1. Adding Desktop Icons
themes, selecting: 15.4.1.3. Theme selector
window managers used with: 15. GNOME
GNOME desktop: 1.5. Sources and Licenses
.gnome-desktop directory: 15.1.1. Adding Desktop Icons
GNOME-RPM: 5.1.2. GNOME-RPM
gnorpm command: 5.1.2. GNOME-RPM
GNU C preprocessor: 3.1. Alphabetical Summary of Commands
GNU Network Object Model Environment (see GNOME)
GNU project: 1.3. Commands on Linux

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Index: H (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: H
h command (sed): 12.5. Alphabetical Summary of sed Commands
halt command: 3.1. Alphabetical Summary of Commands
hardware, commands for: 2.1.3. Hardware
hash command (bash): 7.7. Built-in Commands
hashstat command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
head command: 3.1. Alphabetical Summary of Commands
$Header keyword (RCS): 14.8.1.1. Keywords
Helix GNOME Desktop: 15.4.8. Sawfish Window Manager Configuration
help command (CVS): 14.4.7.9. help
help command (ex): 11.13. Alphabetical Summary of ex Commands
help, Emacs commands for: 10.3.16. Detail Information Help Commands
10.3.16. Detail Information Help Commands
(see also documentation)
help, online: 0.1.4. Online Linux Support
hi/ his commands (CVS) (see history command (CVS))
histdup variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
histfile variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
histlit variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
history, command
bash shell: 7.3.3. Command-line Editing

7.3.3. Command-line Editing
7.4.2. Built-in Shell Variables
csh and tcsh: 8.6. Command History
fc command: 7.7. Built-in Commands
history command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
history command (CVS): 14.4.7.10. history
record types: 14.4.7.10. history
history file (CVS): 14.3.3.7. The history file
history of Linux: 1. Introduction
history variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
$HOME environment variable (CVS): 14.4.2. Configuring CVS

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Index: H (Linux in a Nutshell)
$HOMEDRIVE environment variable (CVS): 14.4.2. Configuring CVS
$HOMEPATH environment variable (CVS): 14.4.2. Configuring CVS
host command: 3.1. Alphabetical Summary of Commands
host machine: 3.1. Alphabetical Summary of Commands
hostid command: 3.1. Alphabetical Summary of Commands
hostname command: 3.1. Alphabetical Summary of Commands
hosts
accessing remote (see telnet)

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Index: I (Linux in a Nutshell)
init command (CVS): 14.3.8.2. init
initrd and RAM disks: 4.6. initrd: Using a RAM Disk
inoclobber variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
input
commands from stdin: 3.1. Alphabetical Summary of Commands

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Index: I (Linux in a Nutshell)
ispell command: 3.1. Alphabetical Summary of Commands

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Index: J (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: J
job control: 8.8. Job Control
jobs: 3.1. Alphabetical Summary of Commands
background/ foreground: 7.7. Built-in Commands
7.7. Built-in Commands
8.8. Job Control
bash shell and: 7.8. Job Control
printing (see printing)
jobs command (bash): 7.7. Built-in Commands
jobs command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
join command: 3.1. Alphabetical Summary of Commands
join command (ex): 11.13. Alphabetical Summary of ex Commands

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Index: K (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: K
k command (ex): 11.13. Alphabetical Summary of ex Commands
kbd_ mode command: 3.1. Alphabetical Summary of Commands
kbdrate command: 3.1. Alphabetical Summary of Commands
KDE (K Desktop Environment): 16. KDE
application windows: 16.1.1. Application Windows
border properties, setting: 16.3.2.2. Borders
color schemes, selecting: 16.3.2.3. Colors
Control Center: 16.3. The KDE Control Center
Applications modules: 16.3.1. Applications
Desktop modules: 16.3.2. Desktop
Information modules: 16.3.3. Information
Input Devices modules: 16.3.4. Input Devices
Keyboard Shortcuts modules: 16.3.5. Keyboard Shortcuts
Sound modules: 16.3.6. Sound
Window Behavior modules: 16.3.7. Window Behavior
Desktop folder: 16.1.4. The Desktop Folder and kdelnk Files
desktop icons
and links: 16.1. Desktop Overview

displaying: 16.3.2.5. Desktop icons
desktop pager: 16.2.1. The Desktop Pager and Window List
font settings: 16.3.2.4. Fonts
installing: 16. KDE
keyboard settings: 16.3.4. Input Devices
16.3.4.1. Keyboard
16.3.7.1. Advanced
kfm (KDE file manager): 16.1.2. kfm--the KDE File Manager
configuration settings for: 16.3.1.2. File manager
cookie management: 16.3.1.3. Web browser
disk navigator and: 16.3.1.4. Panel
web browsing functionality: 16.3.1.3. Web browser
kwm (KDE window manager): 16.2.1. The Desktop Pager and Window List

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Index: K (Linux in a Nutshell)
language settings: 16.3.2.8. Language
login manager: 16.3.1.1. Login manager (root only)
mouse settings: 16.3.4. Input Devices
16.3.4.2. Mouse
16.3.7.3. Mouse
panel: 16.2. The Panel and Taskbar
adding application links to: 16.2.3. Adding an Application Link to the Panel
configuration settings for: 16.3.1.4. Panel
running applications on: 16.2.4. Running an Application on the Panel
screensavers: 16.3.2.9. Screensaver
taskbar: 16.2.2. The Taskbar
theme manager: 16.3.2.7. Theme manager
titlebars: 16.3.7. Window Behavior
tooltips, displaying: 16.3.1.4. Panel
virtual desktops: 16.2.1. The Desktop Pager and Window List
16.3.1.4. Panel
window focus settings: 16.3.7.4. Properties
window list: 16.2.1. The Desktop Pager and Window List
.kdelnk files: 16.1.4. The Desktop Folder and kdelnk Files
disk navigator and: 16.3.1.4. Panel
Kerberos 4 server repository locator: 14.4.1. Repository Locators
kernels: 1.1. The Excitement of Linux
administration commands for: 2.1.8. Managing the Kernel
boot-time options: 4.5. Boot-time Kernel Options
IP firewalling/ masquerading: 2.4. Overview of Firewalls and Masquerading
ipfwadm and: 3.1. Alphabetical Summary of Commands
iptables and: 3.1. Alphabetical Summary of Commands
modular: 4.6. initrd: Using a RAM Disk
printing exported symbols: 3.1. Alphabetical Summary of Commands
setting video mode: 3.1. Alphabetical Summary of Commands
key bindings: 7.7. Built-in Commands
key mappings, KDE: 16.3.5.1. Global keys
keyboard
dumpkeys command: 3.1. Alphabetical Summary of Commands

GNOME settings: 15.4.5.1. Keyboard
KDE settings: 16.3.4.1. Keyboard
16.3.7.1. Advanced
key repeat speed: 3.1. Alphabetical Summary of Commands
mode: 3.1. Alphabetical Summary of Commands
shortcuts (see shortcuts)
Keyboard Shortcuts modules, KDE: 16.3.5. Keyboard Shortcuts

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Index: K (Linux in a Nutshell)
keyword substitutions, CVS: 14.4.6.2. Keyword substitutions
keywords, RCS: 14.8.1. Keyword Substitution
kfm (KDE file manager) (see KDE, kfm)
kill command: 3.1. Alphabetical Summary of Commands
kill command (bash): 7.7. Built-in Commands
kill command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
killall command: 3.1. Alphabetical Summary of Commands
killing processes: 3.1. Alphabetical Summary of Commands
klogd command: 3.1. Alphabetical Summary of Commands
kpanel program: 16.2. The Panel and Taskbar
ksyms command: 3.1. Alphabetical Summary of Commands
kwm (KDE window manager): 16.2.1. The Desktop Pager and Window List

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Index: L (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: L
l command (sed): 12.5. Alphabetical Summary of sed Commands
language settings, KDE: 16.3.2.8. Language
last keyword: 3.1. Alphabetical Summary of Commands
lastlog command: 3.1. Alphabetical Summary of Commands
launcher icons
adding applications to GNOME panel: 15.2.2. Adding an Application Launcher to the

Panel
adding to GNOME desktop: 15.1.1. Adding Desktop Icons
ld (link editor): 3.1. Alphabetical Summary of Commands
ldconfig command: 3.1. Alphabetical Summary of Commands
ldd command: 3.1. Alphabetical Summary of Commands
length command (gawk): 13.8. Alphabetical Summary of Commands
less command: 3.1. Alphabetical Summary of Commands
let command (bash): 7.7. Built-in Commands
lgn command (CVS) (see login command (CVS))
libraries
generating: 3.1. Alphabetical Summary of Commands

linking with: 3.1. Alphabetical Summary of Commands
viewing contents of: 3.1. Alphabetical Summary of Commands
licenses: 1.5. Sources and Licenses
lilo command: 4.2. LILO: The Linux Loader
options: 4.2.2. The lilo Command
LILO (Linux Loader): 1.4. What This Book Offers
4.2. LILO: The Linux Loader
configuration file: 4.2.1. The LILO Configuration File
global options: 4.2.1.1. Global options
image options: 4.2.1.2. Image options
kernel options: 4.2.1.3. Kernel options
limit command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
line addresses (ex): 11.12.1. Options
line-edit mode (bash): 7.6.1. Line-Edit Mode
lines, text

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Index: L (Linux in a Nutshell)
breaking: 3.1. Alphabetical Summary of Commands
comparing: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
counting: 3.1. Alphabetical Summary of Commands
merging into columns: 3.1. Alphabetical Summary of Commands
printing: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
removing duplicate: 3.1. Alphabetical Summary of Commands
searching: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
links (see symbolic links)
links, desktop (see desktop links)
Linux
commands: 1.3. Commands on Linux

1.6. Beginner's Guide
dual booting with Windows systems: 4.2. LILO: The Linux Loader
4.4. Dual Booting Linux and Windows NT/ 2001
history of: 1. Introduction
source code: 1.5. Sources and Licenses
Linux Documentation Project: 0.1.1. Online Documentation
Linux Journal: 0.1.2. Linux Journal and Linux Magazine
Linux Magazine: 0.1.2. Linux Journal and Linux Magazine
Linux User Groups (LUG): 0.1.5. Linux User Groups
list command (ex): 11.13. Alphabetical Summary of ex Commands
listflags variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
listjobs variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
listlinks variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
listmax variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
listmaxrows variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
ln command: 3.1. Alphabetical Summary of Commands
lo command (CVS) (see log command (CVS))
load, system (see performance)
loaders, boot: 4.1. The Boot Process
loading modules: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
unloading: 3.1. Alphabetical Summary of Commands
Loadlin: 1.4. What This Book Offers
booting from MS-DOS: 4.3. Loadlin: Booting from MS-DOS
options: 4.3.2. Putting Parameters on the Command Line
local command (bash): 7.7. Built-in Commands

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Index: L (Linux in a Nutshell)
ls-F command (tcsh): 8.9. Built-in csh and tcsh Commands
lsattr command: 3.1. Alphabetical Summary of Commands
lsmod command: 3.1. Alphabetical Summary of Commands
LUG (Linux User Groups): 0.1.5. Linux User Groups

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Index: M (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: M
M-commands, Emacs: 10.4.2. Meta-Key Sequences
m4 processor: 3.1. Alphabetical Summary of Commands
machine
architecture type: 3.1. Alphabetical Summary of Commands

remote (see remote)
uptime for: 3.1. Alphabetical Summary of Commands
macros
ctags command: 3.1. Alphabetical Summary of Commands

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system: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
to terminals: 3.1. Alphabetical Summary of Commands
writing to all users: 3.1. Alphabetical Summary of Commands
metacharacters: 9.1. Filenames Versus Patterns
9.2. Metacharacters, Listed by Linux Program
filename matching: 8.3.2. Filename Metacharacters
9.1. Filenames Versus Patterns
mime types, setting (GNOME): 15.4.3.2. Mime types
mimencode command: 3.1. Alphabetical Summary of Commands
MINIX filesystems: 3.1. Alphabetical Summary of Commands

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KDE settings: 16.3.4.2. Mouse
16.3.7.3. Mouse
move command (ex): 11.13. Alphabetical Summary of ex Commands
movement commands
Emacs: 10.3.2. Cursor Movement Commands

vi: 11.4. Movement Commands
multimedia settings, GNOME: 15.4.4. Multimedia
mv command: 3.1. Alphabetical Summary of Commands

Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
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Index: N (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: N
n command (sed): 12.5. Alphabetical Summary of sed Commands
name service: 2.3.3. Name Service
named daemon: 3.1. Alphabetical Summary of Commands
namei command: 3.1. Alphabetical Summary of Commands
names
creating file pseudonyms: 3.1. Alphabetical Summary of Commands

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bc language for: 3.1. Alphabetical Summary of Commands
evaluating expressions: 3.1. Alphabetical Summary of Commands
line numbers/ addresses: 11.4.5.1. Line numbering
11.12.1. Options
octal, for permissions: 3.1. Alphabetical Summary of Commands

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Index: O (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: O
obase keyword: 3.1. Alphabetical Summary of Commands
object files
generating: 3.1. Alphabetical Summary of Commands

profile data: 3.1. Alphabetical Summary of Commands
size of: 3.1. Alphabetical Summary of Commands
symbol table for: 3.1. Alphabetical Summary of Commands
octal numbers for permissions: 3.1. Alphabetical Summary of Commands
onintr command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
online documentation (see man pages)
online help: 0.1.4. Online Linux Support
open command (ex): 11.13. Alphabetical Summary of ex Commands
OpenProjects IRC network: 0.1.4. Online Linux Support
operators: 3.1. Alphabetical Summary of Commands
bash shell: 7.4.1. Variable Substitution
7.5.1. Operators
bc language: 3.1. Alphabetical Summary of Commands
csh and tcsh: 8.5.1. Operators
gawk scripting language: 13.5. Operators
ORBit package and GNOME: 15. GNOME
output
echo command (bash): 7.7. Built-in Commands

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Index: O (Linux in a Nutshell)
(see also permissions, file)

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Index: P (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: P
p command (sed): 12.5. Alphabetical Summary of sed Commands
pa| patch commands (CVS) (see rdiff command (CVS))
package flags: 5.2.3. Package Flags
package managers: 5. Red Hat and Debian Package Managers
packaging tools, Debian: 5.2. The Debian Package Manager
Pager module, fvwm2: 17.3. A Modular Approach
multiple desktops, specifying: 17.9. Having Multiple Desktops
panel, KDE (see KDE, panel)
Panel menu, GNOME: 15.2.1. Additional Panels
15.3. The Main Menu
panels, GNOME (see GNOME, panels)
paragraphs, Emacs and: 10.3.4. Paragraphs and Regions
10.3.13. Indentation Commands
parameter files, Loadlin: 4.3.1. Using a Parameter File
parameters
boot: 4.3. Loadlin: Booting from MS-DOS

man page: 3.1. Alphabetical Summary of Commands
$PATH environment variable (CVS): 14.4.2. Configuring CVS

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Index: P (Linux in a Nutshell)
pathchk command: 3.1. Alphabetical Summary of Commands
pattern addressing (sed): 12.3.1. Pattern Addressing
pattern-matching: 7.4.1. Variable Substitution
9. Pattern Matching
bash operators for: 7.4.1. Variable Substitution
gawk language and: 13.3.1. Patterns
patterns, filename (see filename patterns)
PCMCIA sockets, controlling: 3.1. Alphabetical Summary of Commands
pending jobs (see jobs)
performance
CPU load: 3.1. Alphabetical Summary of Commands

graphing system load average: 3.1. Alphabetical Summary of Commands
setting keyboard repeat speed: 3.1. Alphabetical Summary of Commands
Perl
language: 3.1. Alphabetical Summary of Commands

scripts: 5.2.4. Scripts
permissions, file
changing: 3.1. Alphabetical Summary of Commands

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Index: P (Linux in a Nutshell)
program maintenance commands: 1.6.6. Program Maintenance
programming commands: 1.6.5. Programming
programs
debugging (see debugging)

shell scripts: 6.1.3. Programming
.project file: 3.1. Alphabetical Summary of Commands
prompt
customization: 7.6.4. Variables in Prompt

formatting (tcsh): 8.4.4. Formatting for the Prompt Variable
prompt2, prompt3 variables (csh/ tcsh): 8.4.3. Predefined Shell Variables
promptchars variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
protocols, TCP/ IP: 2.3. Overview of TCP/ IP
2.3.2.1. Gateway protocols
ps command: 3.1. Alphabetical Summary of Commands
pserver (CVS): 14.3.8.3. pserver
14.4.1. Repository Locators
accessing repositories: 14.3.3.11. The passwd file
14.3.6. Using an Interim Shared Sandbox
configuring: 14.3.1.1. Setting up the password server
security issues: 14.3.2. Security Issues
pseudonyms for files (see symbolic links)
psupdate command: 3.1. Alphabetical Summary of Commands
pushd command (bash): 7.7. Built-in Commands
pushd command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
pushdsilent variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
pushdtohome variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
put command (ex): 11.13. Alphabetical Summary of ex Commands
PVCS, importing files from: 14.3.5.4. Importing from PVCS
pwck command: 3.1. Alphabetical Summary of Commands
pwconv command: 3.1. Alphabetical Summary of Commands
pwd command: 3.1. Alphabetical Summary of Commands
pwd command (bash): 7.7. Built-in Commands

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Index: Q (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: Q
q command (sed): 12.5. Alphabetical Summary of sed Commands
question mark (see ? (question mark))
queue
job (see jobs)

print (see printing)
quit command (ex): 11.13. Alphabetical Summary of ex Commands
quitting
Emacs commands for: 10.3.5. Stopping and Undoing Commands

vi commands for: 11.6. Saving and Exiting
quoting: 7.3.4. Quoting
8.3.3. Quoting

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Index: R (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: R
r command (sed): 12.5. Alphabetical Summary of sed Commands
RAID devices
setting up: 3.1. Alphabetical Summary of Commands

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Index: R (Linux in a Nutshell)
rdev command: 3.1. Alphabetical Summary of Commands
rdiff command (CVS): 14.4.7.15. rdiff
rdist command: 3.1. Alphabetical Summary of Commands
rdistd daemon: 3.1. Alphabetical Summary of Commands
re| rel commands (CVS) (see release command (CVS))
read command (bash): 7.7. Built-in Commands
read command (ex): 11.13. Alphabetical Summary of ex Commands
read permissions (see permissions, file)
readers file (CVS): 14.3.3.13. The readers file
readonly command (bash): 7.7. Built-in Commands
reboot command: 3.1. Alphabetical Summary of Commands
recexact variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
recognize_ only_ executables variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
recover command (ex): 11.13. Alphabetical Summary of ex Commands
Red Hat Package Manager (RPM): 3.1. Alphabetical Summary of Commands
5.1. The Red Hat Package Manager
GNOME-RPM: 5.1.2. GNOME-RPM
rpm command (see rpm command)
redirection
bash shell and: 7.3.6. Redirection Forms

csh and tcsh: 8.3.5. Redirection Forms
regions, Emacs and: 10.3.4. Paragraphs and Regions
regular expressions: 7.4.1. Variable Substitution
(see also pattern-matching)
searching file contents: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
regular modules: 14.3.3.9. The modules file
rehash command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
release command (CVS): 14.4.7.16. release
remote
access (see telnet)

command execution: 3.1. Alphabetical Summary of Commands
files, copying: 3.1. Alphabetical Summary of Commands
hosts (see hosts)
logging in: 3.1. Alphabetical Summary of Commands
machine, transferring files to/ from: 3.1. Alphabetical Summary of Commands
shell programs (CVS): 14.4.2. Configuring CVS
remove command (CVS): 14.4.7.17. remove
removing (see deleting)
renaming files/ directories: 3.1. Alphabetical Summary of Commands
renice command: 3.1. Alphabetical Summary of Commands

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Index: R (Linux in a Nutshell)
repeat command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
replacing, metacharacters for: 9.4.1. Examples of Searching and Replacing
repositories, CVS (see CVS utility, repositories)
Repository file (CVS): 14.4.4.3. CVS directories
repository locators
pserver: 14.3.3.11. The passwd file

14.3.6. Using an Interim Shared Sandbox
types of: 14.4.1. Repository Locators
reset command: 3.1. Alphabetical Summary of Commands
resources (see documentation)
return command (bash): 7.7. Built-in Commands
return command (gawk): 13.8. Alphabetical Summary of Commands
Reverse Address Resolution Protocol (RARP): 3.1. Alphabetical Summary of Commands
reverse linefeeds, displaying: 3.1. Alphabetical Summary of Commands
reverse output: 3.1. Alphabetical Summary of Commands
revision control
CVS utility: 14. CVS and RCS

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Index: S (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: S
s command (sed): 12.5. Alphabetical Summary of sed Commands
sandboxes, CVS (see CVS utility, sandboxes)
savehist variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
saving, vi commands for: 11.6. Saving and Exiting
Sawfish window manager
focus behavior of windows: 15.4.8.2. Focus behavior

minimizing/ maximizing windows: 15.4.8.3. Minimizing and maximizing
moving and resizing windows: 15.4.8.5. Moving and resizing
placement of new windows: 15.4.8.6. Placement
shaded windows: 15.4.8.2. Focus behavior
tooltips, displaying: 15.4.8.4. Miscellaneous
updating windows: 15.4.8.4. Miscellaneous
window appearance, setting: 15.4.8.1. Appearance
workspaces: 15.4.8.7. Workspaces
scale keyword: 3.1. Alphabetical Summary of Commands
SCCS, importing files from: 14.3.5.3. Importing from SCCS
sched command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
sched variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
screensavers, setting
GNOME: 15.4.1.2. Screensaver

KDE: 16.3.2.9. Screensaver
script command: 3.1. Alphabetical Summary of Commands
script command (ex): 11.13. Alphabetical Summary of ex Commands
scripts
exiting: 7.7. Built-in Commands

gawk for (see gawk scripting language)
running all in directory: 3.1. Alphabetical Summary of Commands
shell/ Perl: 5.2.4. Scripts
Scroll variable (fvwm2): 17.13.1. Keyboard Shortcuts to Navigate the Desktop
searching
for bad blocks: 3.1. Alphabetical Summary of Commands

for commands: 7.7. Built-in Commands

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e2fsck command and: 3.1. Alphabetical Summary of Commands
formatting device as: 3.1. Alphabetical Summary of Commands
tuning the parameters of: 3.1. Alphabetical Summary of Commands
sections
of files: 3.1. Alphabetical Summary of Commands

3.1. Alphabetical Summary of Commands
man pages: 3.1. Alphabetical Summary of Commands
sectors, boot: 4.1. The Boot Process
security
administration commands for: 2.1.12. Security and System Integrity

firewalls and masquerading: 2.4. Overview of Firewalls and Masquerading
ipchains and: 3.1. Alphabetical Summary of Commands
ipfwadm and: 3.1. Alphabetical Summary of Commands
iptables and: 3.1. Alphabetical Summary of Commands
sed editor: 3.1. Alphabetical Summary of Commands
9.4. Examples of Searching
12. The sed Editor
commands (by name): 12.5. Alphabetical Summary of sed Commands
metacharacters for: 9.2. Metacharacters, Listed by Linux Program
sed utility: 1.4. What This Book Offers
select command (bash): 7.7. Built-in Commands
semaphore files: 3.1. Alphabetical Summary of Commands
sendmail
mailq command and: 3.1. Alphabetical Summary of Commands

mailstats command and: 3.1. Alphabetical Summary of Commands

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Index: S (Linux in a Nutshell)
makemap command and: 3.1. Alphabetical Summary of Commands
praliases command and: 3.1. Alphabetical Summary of Commands
serial line communication: 2.3.4.2. Serial-line communication
3.1. Alphabetical Summary of Commands
servers
getting information on: 3.1. Alphabetical Summary of Commands

exporting values of: 7.7. Built-in Commands
shells: 1.4. What This Book Offers
6. The Linux Shells: An Overview
changing login: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
creating for euid: 3.1. Alphabetical Summary of Commands
Emacs shell mode characters: 10.3.12. Special Shell Mode Characters
rshd daemon: 3.1. Alphabetical Summary of Commands
shell scripts: 5.2.4. Scripts
6.1.3. Programming
vi commands for: 11.8. Interacting with the Shell
shift command (bash): 7.7. Built-in Commands
shift command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands

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GNOME: 15.4.4. Multimedia
KDE: 16.3.6. Sound
source code, Linux: 1.5. Sources and Licenses
source command (bash): 7.7. Built-in Commands
source command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
source command (ex): 11.13. Alphabetical Summary of ex Commands
$Source keyword (RCS): 14.8.1.1. Keywords
space characters (see whitespace)
special characters
bash shell: 7.3.4. Quoting

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Index: S (Linux in a Nutshell)
st| stat commands (CVS) (see status command (CVS))
stacking directories: 7.7. Built-in Commands
Stallman, Richard: 1.5. Sources and Licenses
standard input (see input)
standard key mappings, KDE: 16.3.5.2. Standard keys
standard output (see output)
StartsOnDesk option (fvwm2): 17.11. Starting Windows on Different Desktops and Pages
StartsOnPage option (fvwm2): 17.11. Starting Windows on Different Desktops and Pages
startup programs, GNOME: 15.4.6. Session
stat command: 3.1. Alphabetical Summary of Commands
$State keyword (RCS): 14.8.1.1. Keywords
state, revision (RCS): 14.8.4. Specifying States
status command (CVS): 14.4.7.19. status
status-line commands (vi): 11.1.4. Status-Line Commands
status variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
sticky windows, fvwm2: 17.5. A Quick Tour of the fvwm Environment
17.10. Making the Same Window Appear on Every Page
stop command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
stop command (ex): 11.13. Alphabetical Summary of ex Commands
storage commands: 1.6.9. Storage
strace command: 3.1. Alphabetical Summary of Commands
strfile command: 3.1. Alphabetical Summary of Commands
strftime function (gawk): 13.8. Alphabetical Summary of Commands
strings
printing: 3.1. Alphabetical Summary of Commands

3.1. Alphabetical Summary of Commands
translating characters between: 3.1. Alphabetical Summary of Commands
strip command: 3.1. Alphabetical Summary of Commands
stty command: 3.1. Alphabetical Summary of Commands
Style variable (fvwm2)
focus policies: 17.6. Specifying Click-to-Type Focus

starting applications on different desktops: 17.11. Starting Windows on Different
Desktops and Pages
sticky windows and: 17.10. Making the Same Window Appear on Every Page
su command: 3.1. Alphabetical Summary of Commands
sub command (gawk): 13.8. Alphabetical Summary of Commands
substitute command (ex): 11.13. Alphabetical Summary of ex Commands
substitution operators
bash shell: 7.4.1. Variable Substitution

7.6.3. Command Substitution
csh/ tcsh shells: 8.4.1. Variable Substitution

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administration: 2.1. Common Commands
commands for: 2.1.13. Starting and Stopping the System
control messages: 3.1. Alphabetical Summary of Commands
integrity of (see security, administration commands for)
load on (see performance)
printing summary of: 3.1. Alphabetical Summary of Commands
runlevel: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
status: 3.1. Alphabetical Summary of Commands
7.4.2. Built-in Shell Variables
time, setting: 3.1. Alphabetical Summary of Commands
system command (gawk): 13.8. Alphabetical Summary of Commands
system component information, KDE: 16.3.3. Information
System menu, GNOME: 15.3. The Main Menu
system status commands: 1.6.10. System Status
system. fvwm2rc configuration file: 17.2. Configuration Files
menu customization and: 17.14. Customizing Menus
sticky windows and: 17.10. Making the Same Window Appear on Every Page

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systime command (gawk): 13.8. Alphabetical Summary of Commands

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Index: T (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: T
t command (ex): 11.13. Alphabetical Summary of ex Commands
t command (sed): 12.5. Alphabetical Summary of sed Commands
ta| tag commands (CVS): 14.4.7.20. tag
tabs (see whitespace)
tac command: 3.1. Alphabetical Summary of Commands
tag command (ex): 11.13. Alphabetical Summary of ex Commands
Tag file (CVS): 14.4.4.3. CVS directories
taginfo file (CVS): 14.3.3.14. The taginfo file
tagnext command (ex): 11.13. Alphabetical Summary of ex Commands
tagpop command (ex): 11.13. Alphabetical Summary of ex Commands
tagprev command (ex): 11.13. Alphabetical Summary of ex Commands
tags
moving: 14.3.8.1. admin

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Index: T (Linux in a Nutshell)
8. csh and tcsh
tee command: 3.1. Alphabetical Summary of Commands
telinit command: 3.1. Alphabetical Summary of Commands
telltc command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
telnet: 3.1. Alphabetical Summary of Commands
telnetd daemon: 3.1. Alphabetical Summary of Commands
$TEMP environment variable (CVS): 14.4.2. Configuring CVS
Template file (CVS): 14.4.4.3. CVS directories
terminals
bash shell variables for: 7.4.2. Built-in Shell Variables

checking spelling: 3.1. Alphabetical Summary of Commands
files (see files)
whitespace (see whitespace)
text processing commands: 1.6.11. Text Processing
TFTP (Trivial File Transfer Protocol): 3.1. Alphabetical Summary of Commands
tftpd daemon: 3.1. Alphabetical Summary of Commands
themes, selecting
Enlightenment window manager: 15.4.9.7. Themes

GNOME: 15.4.1.3. Theme selector
KDE: 16.3.2.7. Theme manager
tilde (~) command (ex): 11.13. Alphabetical Summary of ex Commands
tiles, GNOME panel: 15.4.2.2. Buttons
time and date
calendar: 3.1. Alphabetical Summary of Commands

current: 3.1. Alphabetical Summary of Commands
CVS date formats: 14.4.6.1. Date formats
scheduling command execution: 3.1. Alphabetical Summary of Commands
setting system: 3.1. Alphabetical Summary of Commands
specifying with RCS: 14.8.3. Specifying the Date
time conversion files: 3.1. Alphabetical Summary of Commands
time zones: 3.1. Alphabetical Summary of Commands

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Index: T (Linux in a Nutshell)
uptime command: 3.1. Alphabetical Summary of Commands
waiting for: 3.1. Alphabetical Summary of Commands
time command (csh/ tcsh): 8.9. Built-in csh and tcsh Commands
time variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
times command (bash): 7.7. Built-in Commands
titlebars
GNOME menu: 15.3. The Main Menu

KDE: 16.3.7. Window Behavior
Sawfish window manager: 15.4.8.1. Appearance
tload command: 3.1. Alphabetical Summary of Commands
$TMP, $TMPDIR environment variables (CVS) (see $TEMP environment variable (CVS))
tolower command (gawk): 13.8. Alphabetical Summary of Commands
tooltips, displaying
Enlightenment window manager: 15.4.9.3. Behavior

Emacs editor: 10.2. Typical Problems
TCP/ IP: 2.3.5. Troubleshooting TCP/ IP
true command: 3.1. Alphabetical Summary of Commands
tune2fs command: 3.1. Alphabetical Summary of Commands
tunelp command: 3.1. Alphabetical Summary of Commands
type command (bash): 7.7. Built-in Commands
typeset command (bash): 7.7. Built-in Commands

Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
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Index: U (Linux in a Nutshell)
up| upd commands (CVS) (see update command (CVS))
update command: 3.1. Alphabetical Summary of Commands
update command (CVS): 14.4.7.22. update
status codes: 14.4.7.22. update
Update. prog file (CVS): 14.4.4.3. CVS directories
uppercase (see case)
UPS (Uninterruptible Power Supply): 3.1. Alphabetical Summary of Commands
uptime command: 3.1. Alphabetical Summary of Commands
URL handlers, setting (GNOME): 15.4.3.3. URL handlers
URL links
GNOME desktop, adding to: 15.1.1. Adding Desktop Icons

KDE desktop, adding to: 16.1.3. Adding a Link to the Desktop
16.1.3. Adding a Link to the Desktop
setting colors for: 16.3.1.2. File manager
User Agent tab, KDE Control Center: 16.3.1.3. Web browser
user groups: 0.1.5. Linux User Groups
user interface settings, GNOME: 15.4.7. User Interface
User menu, GNOME: 15.3. The Main Menu
useradd command: 3.1. Alphabetical Summary of Commands
userdel command: 3.1. Alphabetical Summary of Commands
usermod command: 3.1. Alphabetical Summary of Commands
usernames: 3.1. Alphabetical Summary of Commands
users
administration commands for: 2.1.15. Users

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Index: V (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: V
v command (ex): 11.13. Alphabetical Summary of ex Commands
vacation command: 3.1. Alphabetical Summary of Commands
variables
bash shell and: 7.4. Variables

csh and tcsh: 8.4. Variables
environment (see environment variables)
gawk scripting language: 13.4. gawk System Variables
13.6. Variable and Array Assignments
shell (see shell variables)
verbose variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
verifymsg file (CVS): 14.3.3.16. The verifymsg file
version command (ex): 11.13. Alphabetical Summary of ex Commands
version control
CVS utility: 14. CVS and RCS

RCS utility: 14.5. The RCS Utility
version variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
vi command (ex): 11.13. Alphabetical Summary of ex Commands
vi editor: 1.4. What This Book Offers
3.1. Alphabetical Summary of Commands
11. The vi Editor
metacharacters for: 9.2. Metacharacters, Listed by Linux Program
setting up: 11.14. vi Configuration
vi mode (csh/ tcsh): 8.7.5.2. vi mode
vi-style commands: 7.3.3. Command-line Editing
vidmode command: 3.1. Alphabetical Summary of Commands
viewports, GNOME: 15.1. Desktop Overview
15.4.8.7. Workspaces
Sawfish workspaces and: 15.4.8.7. Workspaces
virtual desktops
Enlightenment window manager: 15.4.9.2. Desktops

15.4.9.6. Backgrounds
GNOME: 15.1. Desktop Overview

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Index: V (Linux in a Nutshell)
KDE: 16.2.1. The Desktop Pager and Window List
16.3.1.4. Panel
virtual screens, fvwm2: 17. An Alternative Window Manager: fvwm2
17.5. A Quick Tour of the fvwm Environment
visiblebell variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
visual command (ex): 11.13. Alphabetical Summary of ex Commands
viusage command (ex): 11.13. Alphabetical Summary of ex Commands

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Emacs indentation commands: 10.3.13. Indentation Commands
fmt command: 3.1. Alphabetical Summary of Commands
tabs to/ from spaces: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands
who command: 3.1. Alphabetical Summary of Commands
whoami command: 3.1. Alphabetical Summary of Commands
Window Behavior modules, KDE: 16.3.7. Window Behavior
window list, KDE: 16.2.1. The Desktop Pager and Window List
window managers

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Index: W (Linux in a Nutshell)
Enlightenment: 15.4.9. Configuring the Enlightenment Window Manager
fvwm2: 17. An Alternative Window Manager: fvwm2
kwm (KDE window manager): 16.2.1. The Desktop Pager and Window List
Sawfish: 15.4.8. Sawfish Window Manager Configuration
selecting one for GNOME: 15.4.1.4. Window manager
used with GNOME: 15. GNOME
windows
Emacs commands for: 10.3.11. Window Commands

Enlightenment window manager
focus and movement settings: 15.4.9.1. Basic options

focus behavior: 15.4.9.3. Behavior
tooltips, displaying: 15.4.9.3. Behavior
KDE
focus settings: 16.3.7.4. Properties

minimizing/ maximizing: 16.3.7.4. Properties
placement of new: 16.3.7.4. Properties
resizing and moving: 16.3.7.4. Properties
tooltips, displaying: 16.3.1.4. Panel
Sawfish window manager
default appearance, setting: 15.4.8.1. Appearance

focus behavior: 15.4.8.2. Focus behavior
minimizing/ maximizing: 15.4.8.3. Minimizing and maximizing
moving and resizing: 15.4.8.5. Moving and resizing
placement of new: 15.4.8.6. Placement
shaded: 15.4.8.2. Focus behavior
tooltips, displaying: 15.4.8.4. Miscellaneous
updating: 15.4.8.4. Miscellaneous
Windows 95/ 98, dual booting with Linux: 4.2. LILO: The Linux Loader
Windows NT/ 2001, dual booting with Linux: 4.4. Dual Booting Linux and Windows
NT/ 2001
WinList module, fvwm2: 17.3. A Modular Approach
17.15. The FvwmWinList: Switching the Focus
making it part of default environment: 17.15.2. Making the FvwmWinList Part of Your
Default Environment
word abbreviation commands, Emacs: 10.3.9. Word Abbreviation Commands
word count: 3.1. Alphabetical Summary of Commands
word substitution (csh/ tcsh): 8.6.3. Word Substitution
wordchars variable (csh/ tcsh): 8.4.3. Predefined Shell Variables
workspaces, Sawfish window manager: 15.4.8.7. Workspaces
wq command (ex): 11.13. Alphabetical Summary of ex Commands
write command: 3.1. Alphabetical Summary of Commands

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Index: W (Linux in a Nutshell)
write command (ex): 11.13. Alphabetical Summary of ex Commands
write permissions (see permissions, file)
writers file (CVS): 14.3.3.17. The writers file
writing: 3.1. Alphabetical Summary of Commands
(see also messages)
to disk: 3.1. Alphabetical Summary of Commands
to terminal: 3.1. Alphabetical Summary of Commands
to users: 3.1. Alphabetical Summary of Commands
3.1. Alphabetical Summary of Commands

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Index: X (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: X
x command (sed): 12.5. Alphabetical Summary of sed Commands
X Consortium: 1.3. Commands on Linux
xargs command: 3.1. Alphabetical Summary of Commands
xbiff program: 17.5. A Quick Tour of the fvwm Environment
17.10. Making the Same Window Appear on Every Page
xclock program: 17.5. A Quick Tour of the fvwm Environment
17.10. Making the Same Window Appear on Every Page
xit command (ex): 11.13. Alphabetical Summary of ex Commands
xload program: 17.5. A Quick Tour of the fvwm Environment
xmkmf utility (imake): 3.1. Alphabetical Summary of Commands
xterm program: 1.4. What This Book Offers

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Index: Y (Linux in a Nutshell)
Symbols | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Index: Y
y command (sed): 12.5. Alphabetical Summary of sed Commands
yacc command: 3.1. Alphabetical Summary of Commands
yank command (ex): 11.13. Alphabetical Summary of ex Commands
yanking and pasting
Emacs: 10.3.3. Deletion Commands

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Colophon (Linux in a Nutshell, 3rd Edition)
Linux in a Nutshell, 3rd
Edition

Colophon
Our look is the result of reader comments, our own experimentation, and feedback from
distribution channels. Distinctive covers complement our distinctive approach to technical
topics, breathing personality and life into potentially dry subjects.

The animal featured on the cover of Linux in a Nutshell is an Arabian horse. Known for its
grace and intelligence, the Arabian is one of the oldest breeds of horse, with evidence of its
existence dating back 5000 years. The Arabian was very instrumental as an ancestor to other
popular breeds, most notably the Thoroughbred in the 17th and 18th centuries. Possibly one of
the more characteristic horse breeds, the typical Arabian has large expressive eyes and
nostrils, small ears, and a short, sturdy back. Its stamina suits it particularly well for endurance
riding, where the breed dominates the sport. Its wonderful temperament makes the Arabian an
all-around favorite riding horse in North America, though it also can be found in more
specialized competitions such as dressage, jumping, and reining.

Edie Freedman designed the cover of this book, using a 19th-century engraving from the
Dover Pictorial Archive. Emma Colby produced the cover layout using QuarkXPress 4.1 with
ITC Garamond font from Adobe. Alicia Cech and David Futato designed the inside layout,
based on a series design by Edie Freedman and Nancy Priest. The print version of this book
was created by translating the SGML source into a set of gtroff macros using a filter
developed at O'Reilly & Associates by Norman Walsh. Steve Talbott designed and wrote the
underlying macro set on the basis of the GNU troff -gs macros; Lenny Muellner adapted them
to SGML and implemented the book design. The GNU groff text formatter version 1.09 was
used to generate PostScript output. The text and heading fonts are ITC Garamond and
MonoType.

Norma Emory copyedited Linux in a Nutshell, Third Edition. Kristine Simmons proofread the
text. Claire Cloutier, Melanie Wang, and Maureen Dempsey provided quality control reviews.
Judy Hoer wrote the index, and Robert Romano and Rhon Porter created the illustrations in
Adobe Photoshop 4.0 and Macromedia Freehand 7.0. Interior composition was done by David
Bell-Feins, James Carter, and Molly Shangraw.

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Colophon (Linux in a Nutshell, 3rd Edition)
Index

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