Text and processing

The comm command

Compares two sorted files and shows in columns which lines are only in the first, only in the second or shared.

Syntax

comm [-1] [-2] [-3] archivo1 archivo2

Most useful options

-1Hides the first file's column
-2Hides the second's column
-3Hides the shared column

Copy-ready examples

$ printf 'a\nb\n' > c1.txt && printf 'b\nc\n' > c2.txt && comm c1.txt c2.txtCompare two lists
$ printf 'a\nb\n' > c1.txt && printf 'b\nc\n' > c2.txt && comm -12 c1.txt c2.txtOnly the shared

You can try them in the browser terminal: it does not touch your computer.

Typical mistakes

  • The files must be sorted: otherwise the result is wrong. Use sort first.

Related commands

diffsortuniq

FAQ

How do I get only what is in both?

With comm -12: it hides the first and second columns.

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