comm Man page

COMM(1) User Commands COMM(1)


comm – compare two sorted files line by line




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.

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

do not check that the input is correctly sorted

separate columns with STR

-z, –zero-terminated
line delimiter is NUL, not newline

–help display this help and exit

output version information and exit

Note, comparisons honor the rules specified by ‘LC_COLLATE’.

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.


Written by Richard M. Stallman and David MacKenzie.


GNU coreutils online help:
Report comm translation bugs to


Copyright © 2016 Free Software Foundation, Inc. License GPLv3+: GNU
GPL version 3 or later .
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.


join, uniq

Full documentation at:
or available locally via: info ‘(coreutils) comm invocation’

GNU coreutils 8.25 February 2016 COMM(1)

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