716e19806c
Add trailing semicolons to the extern variables in the SYNOPSIS section like all of the other manpages with extern variables.
281 lines
6.7 KiB
Groff
281 lines
6.7 KiB
Groff
.\" Copyright (c) 1988, 1991 Regents of the University of California.
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.\" All rights reserved.
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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. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. 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: @(#)getopt.3 6.16 (Berkeley) 4/19/91
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.\" $Id: getopt.3,v 1.5 1993/10/13 17:23:39 jtc Exp $
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.\"
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.Dd April 19, 1991
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.Dt GETOPT 3
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.Os BSD 4.3
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.Sh NAME
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.Nm getopt
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.Nd get option letter from argv
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.Sh SYNOPSIS
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.Fd #include <unistd.h>
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.Ft int
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.Fn getopt "int argc" "char * const *argv" "const char *optstring"
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.Vt extern char *optarg;
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.Vt extern int optind;
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.Vt extern int opterr;
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.Vt extern int optopt;
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.Sh DESCRIPTION
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The
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.Fn getopt
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function gets
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the next
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.Em known
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option character from
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.Fa argv .
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An option character is
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.Em known
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if it has been specified in the string of accepted option characters,
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.Fa optstring .
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.Pp
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The option string
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.Fa optstring
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may contain the following characters; letters and
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letters followed by a colon to indicate an option argument
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is to follow. It does not matter to
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.Fn getopt
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if a following argument has leading white space.
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.Pp
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On return from
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.Fn getopt ,
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.Va optarg
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points to an option argument, if it is anticipated,
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and the variable
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.Va optind
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contains the index to the next
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.Fa argv
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argument for a subsequent call
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to
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.Fn getopt .
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.Pp
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The variable
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.Va opterr
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and
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.Va optind
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are both initialized to 1.
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In order to use
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.Fn getopt
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to evaluate multiple sets of arguments, or to evaluate a single set of
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arguments multiple times,
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.Va optind
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must be initialized to the number of argv entries to be skipped in each
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evaluation.
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.Pp
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The
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.Fn getopt
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function
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returns \-1
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when the argument list is exhausted.
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The interpretation of options in the argument list may be cancelled
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by the option
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.Ql --
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(double dash) which causes
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.Fn getopt
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to signal the end of argument processing and return \-1.
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When all options have been processed (i.e., up to the first non-option
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argument),
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.Fn getopt
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returns \-1.
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.Sh DIAGNOSTICS
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If the
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.Fn getopt
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function encounters an option character that is not contained in
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.Fa optstring ,
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it returns a question mark
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.Pq ?
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character.
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If it detects a missing option argument, it returns a colon
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.Pq \:
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character if the first character of
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.Fa optstring
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is a colon, otherwise it returns a question mark.
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In either case, a diagnostic message is written to
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.Em stderr
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unless the application has set
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.Va opterr
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to zero or the first character of
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.Fa optstring
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is a colon.
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.Sh EXAMPLE
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.\" The following example comes from section E.9.7 of the IEEE 1003.2-90
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.\" standard (POSIX.2).
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The following code fragment shows how one might process the arguments for
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a utility that can take the mutually exclusive options
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.Em a
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and
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.Em b
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and the options
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.Em f
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and
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.Em o ,
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both of which require arguments:
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.Pp
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.Bd -literal -compact
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#include <unistd.h>
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int
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main (argc, argv)
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int argc;
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char *argv[];
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{
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int c, bflg, aflg, errflg = 0;
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char *ifile, *ofile;
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extern char *optarg;
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extern int optind, optopt;
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. . .
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while ((c = getopt(argc, argv, ":abf:o:")) != -1) {
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switch(ch) {
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case 'a':
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if (bflg)
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errflg = 1;
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else
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aflg = 1;
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break;
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case 'b':
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if (aflg)
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errflg = 1;
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else
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bflg = 1;
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break;
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case 'f':
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ifile = optarg;
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break;
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case 'o':
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ofile = optarg;
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break;
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case ':': /* -f or -o without option-arg */
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fprintf (stderr,
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"Option -%c requires an option-argument\\n",
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optopt);
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errflg = 1;
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break;
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case '?':
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fprintf (stderr,
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"Unrecognized option: -%c\\n",
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optopt);
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errflg = 1;
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break;
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}
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}
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if (errflg) {
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fprintf (stderr, "usage: . . .\\n");
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exit (2);
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}
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argc -= optind;
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argv += optind;
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. . .
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}
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.Ed
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.Sh STANDARDS
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The
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.Fn getopt
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function conforms to
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.St -p1003.2-92 .
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.Sh HISTORY
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The
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.Fn getopt
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function appeared
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.Bx 4.3 .
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.Sh BUGS
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The
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.Fn getopt
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function was once specified to return
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.Dv EOF
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instead of \-1.
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This was changed by
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.St -p1003.2-92
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to decouple
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.Fn getopt
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from
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.Pa <stdio.h> .
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.Pp
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Option arguments are allowed to begin with
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.Dq Li \- ;
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this is reasonable but
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reduces the amount of error checking possible.
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.Pp
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A single dash
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.Dq Li -
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may be specified as an character in
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.Fa optstring ,
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however it should
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.Em never
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have an argument associated with it.
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This allows
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.Fn getopt
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to be used with programs that expect
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.Dq Li -
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as an option flag.
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This practice is wrong, and should not be used in any current development.
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It is provided for backward compatibility
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.Em only .
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By default, a single dash causes
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.Fn getopt
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to returns \-1.
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This is, we believe, compatible with System V.
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.Pp
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It is also possible to handle digits as option letters.
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This allows
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.Fn getopt
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to be used with programs that expect a number
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.Pq Dq Li \&-\&3
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as an option.
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This practice is wrong, and should not be used in any current development.
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It is provided for backward compatibility
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.Em only .
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The following code fragment works fairly well.
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.Bd -literal -offset indent
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int length;
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char *p;
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while ((c = getopt(argc, argv, "0123456789")) != -1)
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switch (c) {
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case '0': case '1': case '2': case '3': case '4':
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case '5': case '6': case '7': case '8': case '9':
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p = argv[optind - 1];
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if (p[0] == '-' && p[1] == ch && !p[2])
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length = atoi(++p);
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else
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length = atoi(argv[optind] + 1);
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break;
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}
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}
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.Ed
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