.\"	$OpenBSD: comm.1,v 1.14 2009/02/08 17:15:09 jmc Exp $
.\"	$NetBSD: comm.1,v 1.4 1995/03/26 09:25:50 glass Exp $
.\"
.\" Copyright (c) 1989, 1990, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" This code is derived from software contributed to Berkeley by
.\" the Institute of Electrical and Electronics Engineers, Inc.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" SUCH DAMAGE.
.\"
.\"     @(#)comm.1	8.1 (Berkeley) 6/6/93
.\"
.Dd $Mdocdate: February 8 2009 $
.Dt COMM 1
.Os
.Sh NAME
.Nm comm
.Nd select or reject lines common to two files
.Sh SYNOPSIS
.Nm comm
.Op Fl 123f
.Ar file1 file2
.Sh DESCRIPTION
The
.Nm
utility reads
.Ar file1
and
.Ar file2 ,
which should be
sorted lexically, and produces three text
columns as output: lines only in
.Ar file1 ;
lines only in
.Ar file2 ;
and lines in both files.
.Pp
The filename
.Sq -
means the standard input.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl 1
Suppress printing of column 1.
.It Fl 2
Suppress printing of column 2.
.It Fl 3
Suppress printing of column 3.
.It Fl f
Fold case in line comparisons.
.El
.Pp
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.
.Pp
.Nm
assumes that the files are lexically sorted; all characters
participate in line comparisons.
.\" .Sh ENVIRONMENT
.\" .Bl -tag -width indent
.\" .It Ev LANG
.\" .It Ev LC_ALL
.\" .It Ev LC_CTYPE
.\" .It Ev LC_COLLATE
.\" .It Ev LC_MESSAGES
.\" .El
.Pp
.Ex -std comm
.Sh SEE ALSO
.Xr cmp 1 ,
.Xr diff 1 ,
.Xr sort 1 ,
.Xr uniq 1
.Sh STANDARDS
The
.Nm
utility conforms to
.St -p1003.1-2008 .
.Pp
The flag
.Op Fl f
is an extension to that specification.
.Sh HISTORY
A
.Nm
command appeared in
.At v4 .