COMM(1) User Commands COMM(1)

# [NAME](#NAME)

comm - compare two sorted files line by line

# [SYNOPSIS](#SYNOPSIS)

**comm** \[*OPTION*]... *FILE1 FILE2*

# [DESCRIPTION](#DESCRIPTION)

Compare sorted files FILE1 and FILE2 line by line.

When FILE1 or FILE2 is -, read standard input.

With no options, produce three-column output. Column one contains lines unique to FILE1, column two contains lines unique to FILE2, and column three contains lines common to both files.

**-1**

suppress column 1 (lines unique to FILE1)

**-2**

suppress column 2 (lines unique to FILE2)

**-3**

suppress column 3 (lines that appear in both files)

[**--check-order**](#check)

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

[**--nocheck-order**](#nocheck)

do not check that the input is correctly sorted

[**--output-delimiter=STR**](#output)

separate columns with STR

[**--total**](#total)

output a summary

[**-z, --zero-terminated**](#z,)

line delimiter is NUL, not newline

[**--help**](#help)

display this help and exit

[**--version**](#version)

output version information and exit

Comparisons honor the rules specified by 'LC\_COLLATE'.

# [EXAMPLES](#EXAMPLES)

[comm -12 file1 file2](#comm)

Print only lines present in both file1 and file2.

[comm -3 file1 file2](#comm~2)

Print lines in file1 not in file2, and vice versa.

# [AUTHOR](#AUTHOR)

Written by Richard M. Stallman and David MacKenzie.

# [REPORTING BUGS](#REPORTING_BUGS)

Report bugs to: <bug-coreutils@gnu.org>.  
Report any translation bugs to: <https://translationproject.org/team/>.  
GNU coreutils home page: <https://www.gnu.org/software/coreutils/>  
General help using GNU software: <https://www.gnu.org/gethelp/>

# [COPYRIGHT](#COPYRIGHT)

Copyright © 2026 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](#SEE_ALSO)

[**join**(1)](/man/os/coreutils/join.1), [**uniq**(1)](/man/os/coreutils/uniq.1)

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

October 2026 GNU coreutils 9.12

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Document: comm(1) from coreutils 9.12-r5 (Chainguard OS)
Source: https://git.savannah.gnu.org/git/coreutils.git