join(1) — Linux manual page


JOIN(1)                       User Commands                      JOIN(1)

NAME         top

       join - join lines of two files on a common field

SYNOPSIS         top

       join [OPTION]... FILE1 FILE2

DESCRIPTION         top

       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 blanks.

       When FILE1 or FILE2 (not both) is -, read standard input.

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

       -e STRING
              replace missing (empty) input fields with STRING; I.e.,
              missing fields specified with '-12jo' options

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

       -j FIELD
              equivalent to '-1 FIELD -2 FIELD'

       -o FORMAT
              obey FORMAT while constructing output line

       -t CHAR
              use CHAR as input and output field separator

       -v FILENUM
              like -a FILENUM, but suppress joined output lines

       -1 FIELD
              join on this FIELD of file 1

       -2 FIELD
              join on this FIELD of file 2

              check that the input is correctly sorted, even if all
              input lines are pairable

              do not check that the input is correctly sorted

              treat the first line in each file as field headers, print
              them without trying to pair them

       -z, --zero-terminated
              line delimiter is NUL, not newline

       --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.
       If FORMAT is the keyword 'auto', then the first line of each file
       determines the number of fields output for each line.

       Important: FILE1 and FILE2 must be sorted on the join fields.
       E.g., use "sort -k 1b,1" if 'join' has no options, or use "join
       -t ''" if 'sort' has no options.  Comparisons honor the rules
       specified by 'LC_COLLATE'.  If the input is not sorted and some
       lines cannot be joined, a warning message will be given.

AUTHOR         top

       Written by Mike Haertel.

REPORTING BUGS         top

       GNU coreutils online help:
       Report any translation bugs to

COPYRIGHT         top

       Copyright © 2024 Free Software Foundation, Inc.  License GPLv3+:
       GNU GPL version 3 or later <>.
       This is free software: you are free to change and redistribute
       it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO         top

       comm(1), uniq(1)

       Full documentation <>
       or available locally via: info '(coreutils) join invocation'

COLOPHON         top

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GNU coreutils 9.5              March 2024                        JOIN(1)

Pages that refer to this page: comm(1)uniq(1)