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join - join lines of two files on a common field


join [OPTION]... FILE1 FILE2


For each pair of input lines with identical join fields, write a line to standard output. The default join field is the first, delimited by whitespace. When FILE1 or FILE2 (not both) is -, read standard input.

print unpairable lines coming from file FILENUM, where FILENUM is 1 or 2, corresponding to FILE1 or FILE2

replace missing input fields with EMPTY

-i, --ignore-case ignore differences in case when comparing fields

equivalent to ‘-1 FIELD -2 FIELD’

obey FORMAT while constructing output line

use CHAR as input and output field separator

like -a FILENUM, but suppress joined output lines

join on this FIELD of file 1

join on this FIELD of file 2

--help display this help and exit

output version information and exit

Unless -t CHAR is given, leading blanks separate fields and are ignored, else fields are separated by CHAR. Any FIELD is a field number counted from 1. FORMAT is one or more comma or blank separated specifications, each being ‘FILENUM.FIELD’ or ‘0’. Default FORMAT outputs the join field, the remaining fields from FILE1, the remaining fields from FILE2, all separated by CHAR.

Important: FILE1 and FILE2 must be sorted on the join fields.


Written by Mike Haertel.

Reporting Bugs

Report bugs to <>.


Copyright (C) 2006 Free Software Foundation, Inc. This is free software. You may redistribute copies of it under the terms of the GNU General Public License <>. There is NO WARRANTY, to the extent permitted by law.

See Also

The full documentation for join is maintained as a Texinfo manual. If the info and join programs are properly installed at your site, the command

info join

should give you access to the complete manual.

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