join

Join lines on a common field, writes to standard output a line for each pair of input lines that have identical join fields.

SYNTAX
      join [OPTION]... FILE1 FILE2

Description

Either FILE1 or FILE2 (but not both) can be `-', meaning standard input. FILE1 and FILE2 should be already sorted in increasing textual order on the join fields, using the collating sequence specified by the `LC_COLLATE' locale.

Unless the `-t' option is given, the input should be sorted ignoring blanks at the start of the join field, as in `sort -b'. If the `--ignore-case' option is given, lines should be sorted without regard to the case of characters in the join field, as in `sort
-f'.

The defaults are:
The join field is the first field in each line;
Fields in the input are separated by one or more blanks, with leading blanks on the line ignored;
Fields in the output are separated by a space;
Each output line consists of the join field, the remaining fields from FILE1, then the remaining fields from FILE2.

OPTIONS

`-a FILE-NUMBER'
     Print a line for each unpairable line in file FILE-NUMBER (either
     `1' or `2'), in addition to the normal output.

`-e STRING'
     Replace those output fields that are missing in the input with
     STRING.

`-i'
`--ignore-case'
     Ignore differences in case when comparing keys.  With this option,
     the lines of the input files must be ordered in the same way.  Use
     `sort -f' to produce this ordering.

`-1 FIELD'
`-j1 FIELD'
     Join on field FIELD (a positive integer) of file 1.

`-2 FIELD'
`-j2 FIELD'
     Join on field FIELD (a positive integer) of file 2.

`-j FIELD'
     Equivalent to `-1 FIELD -2 FIELD'.

`-o FIELD-LIST...'
     Construct each output line according to the format in FIELD-LIST.
     Each element in FIELD-LIST is either the single character `0' or
     has the form M.N where the file number, M, is `1' or `2' and N is
     a positive field number.

     A field specification of `0' denotes the join field.  In most
     cases, the functionality of the `0' field spec may be reproduced
     using the explicit M.N that corresponds to the join field.
     However, when printing unpairable lines (using either of the `-a'
     or `-v' options), there is no way to specify the join field using
     M.N in FIELD-LIST if there are unpairable lines in both files.  To
     give `join' that functionality, POSIX invented the `0' field
     specification notation.

     The elements in FIELD-LIST are separated by commas or blanks.
     Multiple FIELD-LIST arguments can be given after a single `-o'
     option; the values of all lists given with `-o' are concatenated
     together.  All output lines - including those printed because of
     any -a or -v option - are subject to the specified FIELD-LIST.

`-t CHAR'
     Use character CHAR as the input and output field separator.

`-v FILE-NUMBER'
     Print a line for each unpairable line in file FILE-NUMBER (either
     `1' or `2'), instead of the normal output.

A nation is not in danger of financial disaster merely because it owes itself money" - Andrew William Mellon

Related commands:

csplit - Split a file into context-determined pieces
cut - Divide a file into several parts
fmt - Reformat paragraph text
fold - Wrap input lines to fit in specified width
head - Output the first part of file(s)
paste - Merge lines of files
split - Split a file into fixed-size pieces
tail - Output the last part of files