.\" Copyright (c) 1989, 1990 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.
.\"
.\" %sccs.include.redist.man%
.\"
.\"     @(#)comm.1	6.7 (Berkeley) 06/27/91
.\"
.Dd 
.Os
.Dt COMM 1
.Sh NAME
.Nm comm
.Nd select or reject lines common to two files
.Sh SYNOPSIS
.Nm comm
.Op Fl 123
.Ar file1 file2
.Sh DESCRIPTION
The
.Nm comm
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 ``-'' means the standard input.
.Pp
The following options are available:
.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.
.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 Comm
assumes that the files are lexically sorted; all characters
participate in line comparisons.
.Pp
.Nm Comm
exits 0 on success, >0 if an error occurred.
.Sh SEE ALSO
.Xr cmp 1 ,
.Xr diff 1 ,
.Xr sort 1 ,
.Xr uniq 1
.Sh STANDARDS
The
.Nm comm
command is expected to be POSIX 1003.2 compatible.