JOIN(1) User Commands JOIN(1)

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 blanks.

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

also print unpairable lines from file FILENUM, where FILENUM is 1 or 2, corresponding to FILE1 or FILE2
replace missing (empty) input fields with STRING; I.e., missing fields specified with '-12jo' options
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
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
line delimiter is NUL, not newline
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.

Written by Mike Haertel.

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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.

comm(1), uniq(1)

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

March 2024 GNU coreutils 9.5