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290 lines
7.4 KiB
Groff
290 lines
7.4 KiB
Groff
.\" 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 8.4 (Berkeley) 4/19/94
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.\"
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.TH GETOPT 3 "26 January 1997" GNO "Library Routines"
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.SH NAME
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.BR getopt
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\- get option character from command line argument list
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.SH SYNOPSIS
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#include <stdlib.h>
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.sp 1
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extern char *\fBoptarg\fR;
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.br
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extern int \fBoptind\fR;
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.br
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extern int \fBoptopt\fR;
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.br
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extern int \fBopterr\fR;
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.br
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extern int \fBoptreset\fR;
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.sp 1
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int
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\fBgetopt\fR (int \fIargc\fR, char * const *\fIargv\fR,
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const char *\fIoptstring\fR);
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.br
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int \fBgetopt_restart\fR (void);
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.SH DESCRIPTION
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This manual page describes the BSD implementation of
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.BR getopt .
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.LP
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The
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.BR getopt
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function incrementally parses a command line argument list
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.I argv
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and returns the next
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.IR known
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option character.
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An option character is
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.IR known
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if it has been specified in the string of accepted option characters,
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.IR optstring .
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.LP
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The option string
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.I 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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.IR x
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recognizes an option
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.BR -x ,
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and an option string
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.BR x:
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recognizes an option and argument
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.BR "-x argument" .
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It does not matter to
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.BR getopt
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if a following argument has leading white space.
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.LP
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On return from
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.BR getopt ,
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.IR 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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.IR optind
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contains the index to the next
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.I argv
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argument for a subsequent call
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to
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.BR getopt .
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The variable
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.IR optopt
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saves the last
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.IR known
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option character returned by
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.BR getopt .
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.LP
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The variable
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.IR opterr
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and
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.IR optind
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are both initialized to 1.
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The
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.IR optind
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variable may be set to another value before a set of calls to
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.BR getopt
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in order to skip over more or less argv entries.
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.LP
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In order to use
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.BR 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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.IR optreset
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must be set to 1 before the second and each additional set of calls to
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.BR getopt ,
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and the variable
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.IR optind
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must be reinitialized.
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.LP
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The
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.BR getopt
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function
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returns an
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.BR EOF
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when the argument list is exhausted, or a non-recognized
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option is encountered.
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The interpretation of options in the argument list may be canceled
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by the option
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.BR "--"
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(double dash) which causes
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.BR getopt
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to signal the end of argument processing and return an
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.BR EOF .
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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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.BR getopt
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returns
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.BR EOF .
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.LP
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The
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.BR getopt_restart
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function sets
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.BR optreset
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and
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.BR optind
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to 1 and returns zero. It is provided for backwards compatibility
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with older versions of GNO, and should be avoided in new code.
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.SH DIAGNOSTICS
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If the
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.BR getopt
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function encounters a character not found in the string
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.IR optarg
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or detects
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a missing option argument it writes an error message and returns
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.BR ?
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to the
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.IR stderr .
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Setting
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.IR opterr
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to a zero will disable these error messages.
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If
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.IR optstring
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has a leading
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.BR \&:
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then a missing option argument causes a
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.BR \&:
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to be returned in addition to suppressing any error messages.
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.LP
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Option arguments are allowed to begin with
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.BR \- ;
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this is reasonable but
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reduces the amount of error checking possible.
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.SH EXTENSIONS
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The
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.IR optreset
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variable was added to make it possible to call the
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.BR getopt
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function multiple times.
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This is an extension to the POSIX 1003.2 specification.
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.LP
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The
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.BR getopt_reset
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function is also an extension, but one that has been deprecated.
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.SH LIMITATIONS
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This implementation of
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.BR getopt
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does not allow one to mix options and non-option arguments; option
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processing will halt as soon as the first non-option argument is
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found. The GNU implementation does not have this limitation, but also
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cannot be restarted. The GNU implementation also allows "long options",
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where the option name may be more than one character.
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.LP
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See the GNO FAQ regarding availability of the GNU implementation of
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.BR getopt
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and
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.BR getopt_long (3)
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for GNO.
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.SH EXAMPLE
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.nf
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extern char *optarg;
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extern int optind;
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int bflag, ch, fd;
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bflag = 0;
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while ((ch = getopt(argc, argv, "bf:")) != EOF)
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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)) < 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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argc -= optind;
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argv += optind;
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.fi
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.SH HISTORY
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The
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.BR getopt
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function appeared 4.3BSD.
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.SH BUGS
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A single dash
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.BR \-
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may be specified as an character in
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.IR optstring ,
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however it should
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.IR never
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have an argument associated with it.
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This allows
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.BR getopt
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to be used with programs that expect
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.BR \-
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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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.IR only .
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By default, a single dash causes
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.BR getopt
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to return
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.BR EOF .
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This is, we believe, compatible with System V.
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.LP
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It is also possible to handle digits as option letters.
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This allows
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.BR getopt
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to be used with programs that expect a number (such as
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.BR \-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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.IR only .
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The following code fragment works in most cases.
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.nf
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int length;
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char *p;
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while ((c = getopt(argc, argv, "0123456789")) != EOF)
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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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.fi
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.SH SEE ALSO
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.BR getsubopt (3),
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.BR getopt_long (3G).
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