Search file(s) for specific text.
SYNTAX grep <options> "Search String" [filename] grep <options> [-e PATTERN] [FILE...] grep <options> [-f FILE] [FILE...] A simple example $grep “Needle in a Haystack” /etc/* OPTIONS -A NUM --after-context=NUM (GNU Extension) Print NUM lines of trailing context after matching lines. -a --text (GNU Extension) Do not suppress output lines that contain binary data. Normally, if the first few bytes of a file indicate that the file contains binary data, grep outputs only a message saying that the file matches the pattern. This option causes grep to act as if the file is a text file, even if it would otherwise be treated as binary. _Warning:_ the result might be binary garbage printed to the terminal, which can have nasty side-effects if the terminal driver interprets some of it as commands. -B NUM --before-context=NUM (GNU Extension) Print NUM lines of leading context before matching lines. -b --byte-offset (GNU Extension) Print the byte offset within the input file before each line of output. When `grep' runs on MS-DOS or MS-Windows, the printed byte offsets depend on whether the `-u' (`--unix-byte-offsets') option is used; see below. -C NUM --context=[NUM] (GNU Extension) Print NUM lines (default 2) of output context. `-c' `--count' Suppress normal output; instead print a count of matching lines for each input file. With the `-v', `--invert-match' option, count non-matching lines. -d ACTION --directories=ACTION (GNU Extension) If an input file is a directory, use ACTION to process it. By default, ACTION is `read', which means that directories are read just as if they were ordinary files (some operating systems and filesystems disallow this, and will cause `grep' to print error messages for every directory). If ACTION is `skip', directories are silently skipped. If ACTION is `recurse', `grep' reads all files under each directory, recursively; this is equivalent to the `-r' option. `-e PATTERN' `--regexp=PATTERN' Use PATTERN as the pattern; useful to protect patterns beginning with a `-'. `-f FILE' `--file=FILE' Obtain patterns from FILE, one per line. The empty file contains zero patterns, and therefore matches nothing. -H --with-filename (GNU Extension) Print the filename for each match. -h --no-filename (GNU Extension) Suppress the prefixing of filenames on output when multiple files are searched. --help (GNU Extension) Print a usage message briefly summarizing these command-line options and the bug-reporting address, then exit. `-i' `--ignore-case' Ignore case distinctions in both the pattern and the input files. -L --files-without-match (GNU Extension) Suppress normal output; instead print the name of each input file from which no output would normally have been printed. The scanning of every file will stop on the first match. `-l' `--files-with-matches' Suppress normal output; instead print the name of each input file from which output would normally have been printed. The scanning of every file will stop on the first match. --mmap (GNU Extension) If possible, ue the `mmap' system call to read input, instead of the default `read' system call. In some situations, `--mmap' yields better performance. However, `--mmap' can cause undefined behavior (including core dumps) if an input file shrinks while `grep' is operating, or if an I/O error occurs. `-n' `--line-number' Prefix each line of output with the line number within its input file. -NUM (GNU Extension) Same as `--context=NUM' lines of leading and trailing context. However, grep will never print any given line more than once. `-q' `--quiet' `--silent' Quiet; suppress normal output. The scanning of every file will stop on the first match. Also see the `-s' or `--no-messages' option. -r --recursive (GNU Extension) For each directory mentioned in the command line, read and process all files in that directory, recursively. This is the same as the `-d recurse' option. `-s' `--no-messages' Suppress error messages about nonexistent or unreadable files. Portability note: unlike GNU `grep', traditional `grep' did not conform to POSIX.2, because traditional `grep' lacked a `-q' option and its `-s' option behaved like GNU `grep''s `-q' option. Shell scripts intended to be portable to traditional `grep' should avoid both `-q' and `-s' and should redirect output to `/dev/null' instead. -U --binary (GNU Extension) Treat the file(s) as binary. By default, under MS-DOS and MS-Windows, `grep' guesses the file type by looking at the contents of the first 32kB read from the file. If `grep' decides the file is a text file, it strips the `CR' characters from the original file contents (to make regular expressions with `^' and `$' work correctly). Specifying `-U' overrules this guesswork, causing all files to be read and passed to the matching mechanism verbatim; if the file is a text file with `CR/LF' pairs at the end of each line, this will cause some regular expressions to fail. This option has no effect on platforms other than MS-DOS and MS-Windows. -u --unix-byte-offsets (GNU Extension) Report Unix-style byte offsets. This switch causes `grep' to report byte offsets as if the file were Unix style text file, i.e., the byte offsets ignore the `CR' characters which were stripped. This will produce results identical to running `grep' on a Unix machine. This option has no effect unless `-b' option is also used; it has no effect on platforms other than MS-DOS and MS-Windows. `-v' `--invert-match' Invert the sense of matching, to select non-matching lines. -V --version (GNU Extension) Print the version number of `grep' to the standard output stream. This version number should be included in all bug reports. -w --word-regexp (GNU Extension) Select only those lines containing matches that form whole words. The test is that the matching substring must either be at the beginning of the line, or preceded by a non-word constituent character. Similarly, it must be either at the end of the line or followed by a non-word constituent character. Word-constituent characters are letters, digits, and the underscore. `-x' `--line-regexp' Select only those matches that exactly match the whole line. -Z --null (GNU Extension) Output a zero byte (the ASCII `NUL' character) instead of the character that normally follows a file name. For example, `grep -lZ' outputs a zero byte after each file name instead of the usual newline. This option makes the output unambiguous, even in the presence of file names containing unusual characters like newlines. This option can be used with commands like `find -print0', `perl -0', `sort -z', and `xargs -0' to process arbitrary file names, even those that contain newline characters. -z --null-data (GNU Extension) Treat the input as a set of lines, each terminated by a zero byte (the ASCII `NUL' character) instead of a newline. Like the `-Z' or `--null' option, this option can be used with commands like `sort -z' to process arbitrary file names. Environment variables Grep's behavior can be affected by setting the following environment variables GREP_OPTIONS - default options LANG - language for messages POSIXLY_CORRECT - Posix behaviour _N_GNU_nonoption_argv_flags_ - ignore an operand see `info' for more on these Diagnostics Normally, exit status is 0 if matches were found, and 1 if no matches were found (the `-v' option inverts the sense of the exit status). Exit status is 2 if there were syntax errors in the pattern, inaccessible input files, or other system errors.
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egrep - Search file(s) for lines that match an extended expression
fgrep - Search file(s) for lines that match a fixed string
gawk - Find and Replace text within file(s)
tr - Translate, squeeze, and/or delete characters