| -a | also print unpairable lines from file FILENUM, where FILENUM is 1 or 2, corresponding to FILE1 or FILE2 |
| -e | 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 | equivalent to '-1 FIELD -2 FIELD' |
| -o | obey FORMAT while constructing output line |
| -t | use CHAR as input and output field separator |
| -v | like -a FILENUM, but suppress joined output lines |
| -1 | join on this FIELD of file 1 |
| -2 | join on this FIELD of file 2 |
| --check-order | check that the input is correctly sorted, even if all input lines are pairable |
| --nocheck-order | do not check that the input is correctly sorted |
| --header | 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 |
| --version | output version information and exit |
NAME
join - join lines of two files on a common field
SYNOPSIS
join [OPTION]... FILE1 FILE2
DESCRIPTION
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-order
check that the input is correctly sorted, even if all input lines are pairable
- --nocheck-order
do not check that the input is correctly sorted
- --header
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
- --version
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
Written by Mike Haertel.
REPORTING BUGS
GNU coreutils online help: <https://www.gnu.org/software/coreutils/> Report any translation bugs to <https://translationproject.org/team/>
SEE ALSO
comm(1), uniq(1)
Full documentation <https://www.gnu.org/software/coreutils/join> or available locally via: info '(coreutils) join invocation'
Packaged by Debian (9.7-3) Copyright © 2025 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.