2004-11-03 13:51:07 +00:00
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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
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2007-06-20 22:33:04 +00:00
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.TH "COMM" 1P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
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2004-11-03 13:51:07 +00:00
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.\" comm
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2007-09-20 06:03:25 +00:00
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.SH PROLOG
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This manual page is part of the POSIX Programmer's Manual.
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The Linux implementation of this interface may differ (consult
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the corresponding Linux manual page for details of Linux behavior),
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or the interface may not be implemented on Linux.
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2004-11-03 13:51:07 +00:00
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.SH NAME
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comm \- select or reject lines common to two files
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.SH SYNOPSIS
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.LP
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\fBcomm\fP \fB[\fP\fB-123\fP\fB]\fP \fIfile1 file2\fP
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.SH DESCRIPTION
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.LP
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The \fIcomm\fP utility shall read \fIfile1\fP and \fIfile2\fP, which
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should be ordered in the current collating sequence, and
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produce three text columns as output: lines only in \fIfile1\fP, lines
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only in \fIfile2\fP, and lines in both files.
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.LP
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If the lines in both files are not ordered according to the collating
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sequence of the current locale, the results are
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unspecified.
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.SH OPTIONS
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.LP
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The \fIcomm\fP utility shall conform to the Base Definitions volume
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of IEEE\ Std\ 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
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.LP
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The following options shall be supported:
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.TP 7
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\fB-1\fP
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Suppress the output column of lines unique to \fIfile1\fP.
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.TP 7
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\fB-2\fP
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Suppress the output column of lines unique to \fIfile2\fP.
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.TP 7
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\fB-3\fP
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Suppress the output column of lines duplicated in \fIfile1\fP and
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\fIfile2\fP.
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.sp
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.SH OPERANDS
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.LP
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The following operands shall be supported:
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.TP 7
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\fIfile1\fP
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A pathname of the first file to be compared. If \fIfile1\fP is \fB'-'\fP,
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the standard input shall be used.
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.TP 7
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\fIfile2\fP
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A pathname of the second file to be compared. If \fIfile2\fP is \fB'-'\fP,
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the standard input shall be used.
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2004-11-03 13:51:07 +00:00
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.sp
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.LP
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If both \fIfile1\fP and \fIfile2\fP refer to standard input or to
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the same FIFO special, block special, or character special
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file, the results are undefined.
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.SH STDIN
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.LP
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The standard input shall be used only if one of the \fIfile1\fP or
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\fIfile2\fP operands refers to standard input. See the
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INPUT FILES section.
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.SH INPUT FILES
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.LP
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The input files shall be text files.
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.SH ENVIRONMENT VARIABLES
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.LP
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The following environment variables shall affect the execution of
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\fIcomm\fP:
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.TP 7
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\fILANG\fP
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Provide a default value for the internationalization variables that
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are unset or null. (See the Base Definitions volume of
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IEEE\ Std\ 1003.1-2001, Section 8.2, Internationalization Variables
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for
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the precedence of internationalization variables used to determine
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the values of locale categories.)
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.TP 7
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\fILC_ALL\fP
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If set to a non-empty string value, override the values of all the
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other internationalization variables.
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.TP 7
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\fILC_COLLATE\fP
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.sp
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Determine the locale for the collating sequence \fIcomm\fP expects
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to have been used when the input files were sorted.
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.TP 7
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\fILC_CTYPE\fP
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Determine the locale for the interpretation of sequences of bytes
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of text data as characters (for example, single-byte as
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opposed to multi-byte characters in arguments and input files).
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.TP 7
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\fILC_MESSAGES\fP
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Determine the locale that should be used to affect the format and
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contents of diagnostic messages written to standard
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error.
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.TP 7
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\fINLSPATH\fP
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Determine the location of message catalogs for the processing of \fILC_MESSAGES
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\&.\fP
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.sp
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.SH ASYNCHRONOUS EVENTS
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.LP
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Default.
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.SH STDOUT
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.LP
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The \fIcomm\fP utility shall produce output depending on the options
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selected. If the \fB-1\fP, \fB-2\fP, and \fB-3\fP
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options are all selected, \fIcomm\fP shall write nothing to standard
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output.
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.LP
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If the \fB-1\fP option is not selected, lines contained only in \fIfile1\fP
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shall be written using the format:
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.sp
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.RS
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.nf
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\fB"%s\\n", <\fP\fIline in file1\fP\fB>
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\fP
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.fi
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.RE
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.LP
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If the \fB-2\fP option is not selected, lines contained only in \fIfile2\fP
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are written using the format:
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.sp
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.RS
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.nf
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\fB"%s%s\\n", <\fP\fIlead\fP\fB>, <\fP\fIline in file2\fP\fB>
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\fP
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.fi
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.RE
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.LP
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where the string <\fIlead\fP> is as follows:
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.TP 7
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<tab>
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The \fB-1\fP option is not selected.
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.TP 7
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null\ string
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The \fB-1\fP option is selected.
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.sp
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.LP
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If the \fB-3\fP option is not selected, lines contained in both files
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shall be written using the format:
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.sp
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.RS
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.nf
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\fB"%s%s\\n", <\fP\fIlead\fP\fB>, <\fP\fIline in both\fP\fB>
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\fP
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.fi
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.RE
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.LP
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where the string <\fIlead\fP> is as follows:
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.TP 7
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<tab><tab>
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Neither the \fB-1\fP nor the \fB-2\fP option is selected.
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.TP 7
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<tab>
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Exactly one of the \fB-1\fP and \fB-2\fP options is selected.
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.TP 7
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null\ string
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Both the \fB-1\fP and \fB-2\fP options are selected.
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.sp
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.LP
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If the input files were ordered according to the collating sequence
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of the current locale, the lines written shall be in the
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collating sequence of the original lines.
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.SH STDERR
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.LP
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The standard error shall be used only for diagnostic messages.
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.SH OUTPUT FILES
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.LP
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None.
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.SH EXTENDED DESCRIPTION
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.LP
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None.
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.SH EXIT STATUS
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.LP
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The following exit values shall be returned:
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.TP 7
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\ 0
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All input files were successfully output as specified.
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.TP 7
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>0
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An error occurred.
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.sp
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.SH CONSEQUENCES OF ERRORS
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.LP
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Default.
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.LP
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\fIThe following sections are informative.\fP
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.SH APPLICATION USAGE
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.LP
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If the input files are not properly presorted, the output of \fIcomm\fP
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might not be useful.
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.SH EXAMPLES
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.LP
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If a file named \fBxcu\fP contains a sorted list of the utilities
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in this volume of IEEE\ Std\ 1003.1-2001, a file
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named \fBxpg3\fP contains a sorted list of the utilities specified
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in the X/Open Portability Guide, Issue 3, and a file named
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\fBsvid89\fP contains a sorted list of the utilities in the System
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V Interface Definition Third Edition:
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.sp
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.RS
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.nf
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\fBcomm -23 xcu xpg3 | comm -23 - svid89
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\fP
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.fi
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.RE
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.LP
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would print a list of utilities in this volume of IEEE\ Std\ 1003.1-2001
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not specified by either of the other
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documents:
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.sp
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.RS
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.nf
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\fBcomm -12 xcu xpg3 | comm -12 - svid89
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\fP
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.fi
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.RE
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.LP
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would print a list of utilities specified by all three documents,
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and:
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.sp
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.RS
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.nf
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\fBcomm -12 xpg3 svid89 | comm -23 - xcu
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\fP
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.fi
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.RE
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.LP
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would print a list of utilities specified by both XPG3 and the SVID,
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but not specified in this volume of
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IEEE\ Std\ 1003.1-2001.
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.SH RATIONALE
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.LP
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None.
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.SH FUTURE DIRECTIONS
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.LP
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None.
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.SH SEE ALSO
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.LP
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2007-09-20 06:36:16 +00:00
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\fIcmp\fP, \fIdiff\fP, \fIsort\fP, \fIuniq\fP
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2004-11-03 13:51:07 +00:00
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.SH COPYRIGHT
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Portions of this text are reprinted and reproduced in electronic form
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from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
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-- Portable Operating System Interface (POSIX), The Open Group Base
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Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
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Electrical and Electronics Engineers, Inc and The Open Group. In the
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event of any discrepancy between this version and the original IEEE and
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The Open Group Standard, the original IEEE and The Open Group Standard
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is the referee document. The original Standard can be obtained online at
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http://www.opengroup.org/unix/online.html .
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