COMM(1)                   BSD General Commands Manual                  COMM(1)

NAME
     comm -- select or reject lines common to two files

SYNOPSIS
     comm [-123i] file1 file2

DESCRIPTION
     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 following options are available:

     -1      Suppress printing of column 1.

     -2      Suppress printing of column 2.

     -3      Suppress printing of column 3.

     -i      Case insensitive comparison of lines.

     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 exam-
     ple, 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.

     The comm utility assumes that the files are lexically sorted; all charac-
     ters participate in line comparisons.

ENVIRONMENT
     The LANG, LC_ALL, LC_COLLATE, and LC_CTYPE environment variables affect
     the execution of comm as described in environ(7).

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

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

STANDARDS
     The comm utility conforms to IEEE Std 1003.2-1992 (``POSIX.2'').

     The -i option is an extension to the POSIX standard.

HISTORY
     A comm command appeared in Version 4 AT&T UNIX.

BUGS
     Input lines are limited to LINE_MAX(2048) characters in length.

BSD                            January 26, 2005                            BSD