join: Join lines on a common field
join writes to standard output a line for each pair of input
lines that have identical join fields. Synopsis:
join [option]... file1 file2
Either file1 or file2 (but not both) can be `-',
meaning standard input. file1 and file2 should be already
sorted in increasing order (not numerically) on the join fields; unless
the `-t' option is given, they 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
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.
The program accepts the following options. Also see section Common options.
jointhat 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.
In addition, when GNU
join is invoked with exactly one argument,
options `--help' and `--version' are recognized. See section Common options.
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