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COMM

Section: User Commands (1)
Updated: February 2026
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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 (not both) 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.

X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#com-1'-1X'tty: link'

suppress column 1 (lines unique to FILE1)

X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#com-2'-2X'tty: link'

suppress column 2 (lines unique to FILE2)

X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#com-3'-3X'tty: link'

suppress column 3 (lines that appear in both files)

X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#com-chec-order'--check-orderX'tty: link'

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

X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#com-nochec-order'--nocheck-orderX'tty: link'

do not check that the input is correctly sorted

X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#com-outpu-delimiter'--output-delimiter=STRX'tty: link'

separate columns with STR

X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#com-total'--totalX'tty: link'

output a summary

X'tty: link https://www.gnu.org/software/coreutils/manual/coreutils.html#com-z'-z, --zero-terminatedX'tty: link'

line delimiter is NUL, not newline

X'tty: link https://www.gnu.org/software/coreutils/comm#com-help'--helpX'tty: link'

display this help and exit

X'tty: link https://www.gnu.org/software/coreutils/comm#com-version'--versionX'tty: link'

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

SEE ALSO

join(1), uniq(1)

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

Packaged by Gentoo (9.10 (p0))
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.

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Index

NAME

SYNOPSIS

DESCRIPTION

EXAMPLES

AUTHOR

REPORTING BUGS

SEE ALSO