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COMM(1) General Commands Manual COMM(1)

select or reject lines common to two files

comm [
] file1 file2

The comm utility reads file1 and file2, which should be sorted lexically, and produces three text columns as output: lines only in file1; lines only in file2; and lines in both files.
The filename ‘-’ means the standard input.
The options are as follows:
Suppress printing of column 1.
Suppress printing of column 2.
Suppress printing of column 3.
Fold case in line comparisons.
Each column will have a number of tab characters prepended to it equal to the number of lower numbered columns that are being printed. For example, if column number two is being suppressed, lines printed in column number one will not have any tabs preceding them, and lines printed in column number three will have one.
comm assumes that the files are lexically sorted; all characters participate in line comparisons.

The comm utility exits 0 on success, and >0 if an error occurs.

cmp(1), diff(1), sort(1), uniq(1)

The comm utility conforms to IEEE Std 1003.1-2008 (“POSIX.1”).
The flag [
] is an extension to that specification.

A comm command appeared in Version 4 AT&T UNIX.
September 3, 2010 OpenBSD-current