145 lines
3.7 KiB
Groff
145 lines
3.7 KiB
Groff
.\" Copyright (c) 1989, 1990, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" This code is derived from software contributed to Berkeley by
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.\" the Institute of Electrical and Electronics Engineers, Inc.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" From: @(#)comm.1 8.1 (Berkeley) 6/6/93
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.\"
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.Dd July 27, 2020
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.Dt COMM 1
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.Os
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.Sh NAME
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.Nm comm
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.Nd select or reject lines common to two files
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.Sh SYNOPSIS
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.Nm
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.Op Fl 123i
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.Ar file1 file2
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.Sh DESCRIPTION
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The
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.Nm
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utility reads
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.Ar file1
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and
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.Ar file2 ,
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which should be
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sorted lexically, and produces three text
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columns as output: lines only in
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.Ar file1 ;
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lines only in
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.Ar file2 ;
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and lines in both files.
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.Pp
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The filename ``-'' means the standard input.
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.Pp
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The following options are available:
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.Bl -tag -width indent
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.It Fl 1
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Suppress printing of column 1, lines only in
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.Ar file1 .
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.It Fl 2
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Suppress printing of column 2, lines only in
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.Ar file2 .
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.It Fl 3
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Suppress printing of column 3, lines common to both.
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.It Fl i
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Case insensitive comparison of lines.
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.El
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.Pp
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Each column will have a number of tab characters prepended to it
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equal to the number of lower numbered columns that are being printed.
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For example, if column number two is being suppressed, lines printed
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in column number one will not have any tabs preceding them, and lines
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printed in column number three will have one.
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.Pp
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The
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.Nm
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utility assumes that the files are lexically sorted; all characters
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participate in line comparisons.
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.Sh ENVIRONMENT
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The
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.Ev LANG ,
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.Ev LC_ALL ,
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.Ev LC_COLLATE ,
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and
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.Ev LC_CTYPE
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environment variables affect the execution of
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.Nm
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as described in
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.Xr environ 7 .
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.Sh EXIT STATUS
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.Ex -std
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.Sh EXAMPLES
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Assuming a file named
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.Pa example.txt
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with the following contents:
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.Bd -literal -offset indent
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a
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b
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c
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d
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.Ed
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.Pp
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Show lines only in
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.Pa example.txt ,
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lines only in stdin and common lines:
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.Bd -literal -offset indent
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$ echo -e "B\enc" | comm example.txt -
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B
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a
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b
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c
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d
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.Ed
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.Pp
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Show only common lines doing case insensitive comparisons:
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.Bd -literal -offset indent
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$ echo -e "B\enc" | comm -1 -2 -i example.txt -
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b
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c
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.Ed
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.Sh SEE ALSO
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.Xr cmp 1 ,
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.Xr diff 1 ,
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.Xr sort 1 ,
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.Xr uniq 1
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.Sh STANDARDS
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The
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.Nm
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utility conforms to
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.St -p1003.2-92 .
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.Pp
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The
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.Fl i
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option is an extension to the POSIX standard.
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.Sh HISTORY
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A
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.Nm
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command appeared in
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.At v4 .
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