freebsd-skq/usr.bin/comm/comm.1

.\" 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
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     From: @(#)comm.1	8.1 (Berkeley) 6/6/93
.\" $FreeBSD$
.\"
.Dd July 27, 2020
.Dt COMM 1
.Os
.Sh NAME
.Nm comm
.Nd select or reject lines common to two files
.Sh SYNOPSIS
.Nm
.Op Fl 123i
.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 ``-'' means the standard input.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl 1
Suppress printing of column 1, lines only in
.Ar file1 .
.It Fl 2
Suppress printing of column 2, lines only in
.Ar file2 .
.It Fl 3
Suppress printing of column 3, lines common to both.
.It Fl i
Case insensitive comparison of lines.
.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
The
.Nm
utility assumes that the files are lexically sorted; all characters
participate in line comparisons.
.Sh ENVIRONMENT
The
.Ev LANG ,
.Ev LC_ALL ,
.Ev LC_COLLATE ,
and
.Ev LC_CTYPE
environment variables affect the execution of
.Nm
as described in
.Xr environ 7 .
.Sh EXIT STATUS
.Ex -std
.Sh EXAMPLES
Assuming a file named
.Pa example.txt
with the following contents:
.Bd -literal -offset indent
a
b
c
d
.Ed
.Pp
Show lines only in
.Pa example.txt ,
lines only in stdin and common lines:
.Bd -literal -offset indent
$ echo -e "B\enc" | comm example.txt -
        B
a
b
                c
d
.Ed
.Pp
Show only common lines doing case insensitive comparisons:
.Bd -literal -offset indent
$ echo -e "B\enc" | comm -1 -2 -i example.txt -
b
c
.Ed
.Sh SEE ALSO
.Xr cmp 1 ,
.Xr diff 1 ,
.Xr sort 1 ,
.Xr uniq 1
.Sh STANDARDS
The
.Nm
utility conforms to
.St -p1003.2-92 .
.Pp
The
.Fl i
option is an extension to the POSIX standard.
.Sh HISTORY
A
.Nm
command appeared in
.At v4 .