# phpman > man > JOIN(1)

> **TLDR:** Join lines of two sorted files on a common field.
>
- Join two files on the first (default) field:
  `join {{path/to/file1}} {{path/to/file2}}`
- Join two files using a comma (instead of a space) as the field separator:
  `join -t ',' {{path/to/file1}} {{path/to/file2}}`
- Join field3 of file1 with field1 of file2:
  `join -1 {{3}} -2 {{1}} {{path/to/file1}} {{path/to/file2}}`
- Produce a line for each unpairable line for file1:
  `join -a {{1}} {{path/to/file1}} {{path/to/file2}}`
- Join a file from `stdin`:
  `cat {{path/to/file1}} | join - {{path/to/file2}}`

*Source: tldr-pages*

---

[JOIN(1)](https://www.chedong.com/phpMan.php/man/JOIN/1/markdown)                                     User Commands                                    [JOIN(1)](https://www.chedong.com/phpMan.php/man/JOIN/1/markdown)



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

### -e
              replace missing input fields with EMPTY

### -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

       Unless **-t** CHAR is given, leading blanks separate fields and are ignored, else fields are sep‐
       arated  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 sepa‐
       rated 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.  Note, 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/>>

## COPYRIGHT
       Copyright © 2020 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.

## SEE ALSO
       [comm(1)](https://www.chedong.com/phpMan.php/man/comm/1/markdown), [uniq(1)](https://www.chedong.com/phpMan.php/man/uniq/1/markdown)

       Full documentation <<https://www.gnu.org/software/coreutils/join>>
       or available locally via: info '(coreutils) join invocation'



GNU coreutils 8.32                          January 2026                                     [JOIN(1)](https://www.chedong.com/phpMan.php/man/JOIN/1/markdown)