---
name: "comm"
section: "1"
platform: "linux"
package: "coreutils"
version: "9.12-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "freebsd", "openbsd", "macos"]
url: "https://new.carta.tech/comm"
---

# comm(1)

compare two sorted files line by line

## NAME

comm - compare two sorted files line by line

## SYNOPSIS

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

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

- **--nocheck-order**

  do not check that the input is correctly sorted

- **--output-delimiter=STR**

  separate columns with STR

- **--total**

  output a summary

- **-z, --zero-terminated**

  line delimiter is NUL, not newline

- **--help**

  display this help and exit

- **--version**

  output version information and exit

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

## EXAMPLES

- comm -12 file1 file2

  Print only lines present in both file1 and file2.

- comm -3 file1 file2

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

## AUTHOR

Written by Richard M. Stallman and David MacKenzie.

## 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 © 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

[**join**(1)](/join/1.md), [**uniq**(1)](/uniq/1.md)

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