d68c1e59a8
example. The externs haven't been needed in about 10 years, so there's no reason to have them other than for hysterical raisins. And the California Rasins haven't been around for a long time...
311 lines
7.6 KiB
Groff
311 lines
7.6 KiB
Groff
.\" $NetBSD: getopt.3,v 1.31 2003/09/23 10:26:54 wiz Exp $
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.\"
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.\" Copyright (c) 1988, 1991, 1993
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.\" The Regents of the University of California. 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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.\" @(#)getopt.3 8.5 (Berkeley) 4/27/95
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.\" $FreeBSD$
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.\"
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.Dd April 27, 1995
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.Dt GETOPT 3
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.Os
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.Sh NAME
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.Nm getopt
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.Nd get option character from command line argument list
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In unistd.h
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.Vt extern char *optarg ;
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.Vt extern int optind ;
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.Vt extern int optopt ;
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.Vt extern int opterr ;
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.Vt extern int optreset ;
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.Ft int
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.Fn getopt "int argc" "char * const argv[]" "const char *optstring"
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.Sh DESCRIPTION
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The
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.Fn getopt
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function incrementally parses a command line argument list
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.Fa argv
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and returns the next
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.Em known
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option character.
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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 elements: individual characters, and
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characters followed by a colon to indicate an option argument
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is to follow.
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For example, an option string
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.Li "\&""x""
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recognizes an option
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.Dq Fl x ,
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and an option string
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.Li "\&""x:""
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recognizes an option and argument
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.Dq Fl x Ar argument .
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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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The variable
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.Va optopt
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saves the last
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.Em known
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option character returned by
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.Fn getopt .
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.Pp
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The variables
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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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The
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.Va optind
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variable may be set to another value before a set of calls to
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.Fn getopt
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in order to skip over more or less argv entries.
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.Pp
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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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the variable
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.Va optreset
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must be set to 1 before the second and each additional set of calls to
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.Fn getopt ,
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and the variable
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.Va optind
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must be reinitialized.
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.Pp
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The
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.Fn getopt
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function returns \-1 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 RETURN VALUES
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The
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.Fn getopt
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function returns the next known option character in
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.Fa optstring .
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If
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.Fn getopt
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encounters a character not found in
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.Fa optstring
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or if it detects a missing option argument,
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it returns
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.Ql \&?
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(question mark).
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If
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.Fa optstring
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has a leading
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.Ql \&:
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then a missing option argument causes
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.Ql \&:
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to be returned instead of
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.Ql \&? .
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In either case, the variable
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.Va optopt
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is set to the character that caused the error.
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The
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.Fn getopt
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function returns \-1 when the argument list is exhausted.
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.Sh EXAMPLES
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.Bd -literal -compact
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#include <unistd.h>
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int bflag, ch, fd;
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bflag = 0;
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while ((ch = getopt(argc, argv, "bf:")) != -1) {
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switch (ch) {
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case 'b':
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bflag = 1;
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break;
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case 'f':
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if ((fd = open(optarg, O_RDONLY, 0)) \*[Lt] 0) {
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(void)fprintf(stderr,
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"myname: %s: %s\en", optarg, strerror(errno));
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exit(1);
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}
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break;
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case '?':
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default:
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usage();
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}
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}
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argc -= optind;
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argv += optind;
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.Ed
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.Sh DIAGNOSTICS
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If the
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.Fn getopt
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function encounters a character not found in the string
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.Fa optstring
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or detects
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a missing option argument it writes an error message to the
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.Dv stderr
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and returns
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.Ql \&? .
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Setting
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.Va opterr
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to a zero will disable these error messages.
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If
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.Fa optstring
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has a leading
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.Ql \&:
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then a missing option argument causes a
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.Ql \&:
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to be returned in addition to suppressing any error messages.
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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 reduces the amount of error checking possible.
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.Sh SEE ALSO
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.Xr getopt 1 ,
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.Xr getopt_long 3 ,
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.Xr getsubopt 3
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.Sh STANDARDS
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The
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.Va optreset
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variable was added to make it possible to call the
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.Fn getopt
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function multiple times.
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This is an extension to the
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.St -p1003.2
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specification.
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.Sh HISTORY
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The
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.Fn getopt
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function appeared in
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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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.In stdio.h .
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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 a 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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Care should be taken not to use
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.Ql \&-
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as the first character in
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.Fa optstring
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to avoid a semantic conflict with
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.Tn GNU
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.Fn getopt ,
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which assigns different meaning to an
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.Fa optstring
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that begins with a
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.Ql \&- .
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By default, a single dash causes
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.Fn getopt
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to return \-1.
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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 in most cases.
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.Bd -literal -offset indent
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int ch;
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long length;
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char *p, *ep;
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while ((ch = getopt(argc, argv, "0123456789")) != -1)
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switch (ch) {
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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] == '-' \*[Am]\*[Am] p[1] == ch \*[Am]\*[Am] !p[2]) {
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length = ch - '0';
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ep = "";
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} else if (argv[optind] \*[Am]\*[Am] argv[optind][1] == ch) {
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length = strtol((p = argv[optind] + 1),
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\*[Am]ep, 10);
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optind++;
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optreset = 1;
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} else
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usage();
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if (*ep != '\e0')
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errx(EX_USAGE, "illegal number -- %s", p);
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break;
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}
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.Ed
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