445 lines
9.7 KiB
Groff
445 lines
9.7 KiB
Groff
.\" $OpenBSD: getopt_long.3,v 1.21 2016/01/04 19:43:13 tb Exp $
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.\" $NetBSD: getopt_long.3,v 1.11 2002/10/02 10:54:19 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. 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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.\"
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.Dd $Mdocdate: January 4 2016 $
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.Dt GETOPT_LONG 3
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.Os
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.Sh NAME
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.Nm getopt_long ,
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.Nm getopt_long_only
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.Nd get long options from command line argument list
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.Sh SYNOPSIS
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.In getopt.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_long "int argc" "char * const *argv" "const char *optstring" "const struct option *longopts" "int *longindex"
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.Ft int
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.Fn getopt_long_only "int argc" "char * const *argv" "const char *optstring" "const struct option *longopts" "int *longindex"
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.Sh DESCRIPTION
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The
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.Fn getopt_long
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function is similar to
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.Xr getopt 3
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but it accepts options in two forms: words and characters.
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The
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.Fn getopt_long
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function provides a superset of the functionality of
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.Xr getopt 3 .
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.Fn getopt_long
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can be used in two ways.
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In the first way, every long option understood by the program has a
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corresponding short option, and the option structure is only used to
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translate from long options to short options.
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When used in this fashion,
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.Fn getopt_long
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behaves identically to
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.Xr getopt 3 .
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This is a good way to add long option processing to an existing program
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with the minimum of rewriting.
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.Pp
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In the second mechanism, a long option sets a flag in the
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.Fa option
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structure passed, or will store a pointer to the command line argument
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in the
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.Fa option
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structure passed to it for options that take arguments.
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Additionally, the long option's argument may be specified as a single
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argument with an equal sign, e.g.
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.Bd -literal -offset indent
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$ myprogram --myoption=somevalue
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.Ed
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.Pp
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When a long option is processed, the call to
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.Fn getopt_long
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will return 0.
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For this reason, long option processing without
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shortcuts is not backwards compatible with
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.Xr getopt 3 .
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.Pp
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It is possible to combine these methods, providing for long options
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processing with short option equivalents for some options.
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Less frequently used options would be processed as long options only.
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.Pp
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Abbreviated long option names are accepted when
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.Fn getopt_long
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processes long options if the abbreviation is unique.
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An exact match is always preferred for a defined long option.
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.Pp
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The
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.Fn getopt_long
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call requires an array to be initialized describing the long
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options.
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Each element of the array is a structure:
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.Bd -literal -offset indent
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struct option {
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char *name;
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int has_arg;
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int *flag;
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int val;
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};
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.Ed
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.Pp
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The
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.Fa name
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field should contain the option name without the leading double dash.
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.Pp
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The
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.Fa has_arg
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field should be one of:
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.Pp
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.Bl -tag -width "optional_argument" -compact -offset indent
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.It Dv no_argument
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no argument to the option is expected.
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.It Dv required_argument
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an argument to the option is required.
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.It Dv optional_argument
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an argument to the option may be presented.
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.El
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.Pp
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If
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.Fa flag
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is not
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.Dv NULL ,
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then the integer pointed to by it will be set to the value in the
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.Fa val
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field.
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If the
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.Fa flag
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field is
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.Dv NULL ,
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then the
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.Fa val
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field will be returned.
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Setting
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.Fa flag
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to
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.Dv NULL
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and setting
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.Fa val
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to the corresponding short option will make this function act just
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like
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.Xr getopt 3 .
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.Pp
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If the
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.Fa longindex
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field is not
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.Dv NULL ,
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then the integer pointed to by it will be set to the index of the long
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option relative to
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.Fa longopts .
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.Pp
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The last element of the
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.Fa longopts
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array has to be filled with zeroes.
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.Pp
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The
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.Fn getopt_long_only
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function behaves identically to
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.Fn getopt_long
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with the exception that long options may start with
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.Sq -
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in addition to
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.Sq -- .
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If an option starting with
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.Sq -
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does not match a long option but does match a single-character option,
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the single-character option is returned.
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.Sh RETURN VALUES
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If the
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.Fa flag
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field in
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.Li struct option
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is
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.Dv NULL ,
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.Fn getopt_long
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and
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.Fn getopt_long_only
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return the value specified in the
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.Fa val
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field, which is usually just the corresponding short option.
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If
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.Fa flag
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is not
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.Dv NULL ,
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these functions return 0 and store
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.Fa val
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in the location pointed to by
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.Fa flag .
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These functions return
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.Sq \&:
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if there was a missing option argument,
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.Sq \&?
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if the user specified an unknown or ambiguous option, and
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\-1 when the argument list has been exhausted.
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.Sh IMPLEMENTATION DIFFERENCES
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This section describes differences to the GNU implementation
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found in glibc-2.1.3:
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.Bl -bullet
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.It
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handling of
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.Ql -
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within the option string (not the first character):
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.Bl -tag -width "OpenBSD"
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.It GNU
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treats a
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.Ql -
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on the command line as a non-argument.
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.It OpenBSD
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a
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.Ql -
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within the option string matches a
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.Ql -
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(single dash) on the command line.
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This functionality is provided for backward compatibility with
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programs, such as
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.Xr su 1 ,
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that use
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.Ql -
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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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.El
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.It
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handling of
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.Ql ::
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in the option string in the presence of
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.Ev POSIXLY_CORRECT :
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.Bl -tag -width "OpenBSD"
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.It Both
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GNU and
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.Ox
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ignore
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.Ev POSIXLY_CORRECT
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here and take
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.Ql ::
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to mean the preceding option takes an optional argument.
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.El
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.It
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return value in case of missing argument if first character
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(after
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.Ql +
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or
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.Ql - )
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in the option string is not
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.Ql \&: :
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.Bl -tag -width "OpenBSD"
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.It GNU
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returns
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.Ql \&?
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.It OpenBSD
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returns
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.Ql \&:
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(since
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.Ox Ns 's
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.Xr getopt 3
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does).
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.El
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.It
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handling of
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.Ql --a
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in
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.Xr getopt 3 :
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.Bl -tag -width "OpenBSD"
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.It GNU
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parses this as option
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.Ql - ,
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option
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.Ql a .
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.It OpenBSD
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parses this as
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.Ql -- ,
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and returns \-1 (ignoring the
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.Ql a )
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(because the original
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.Fn getopt
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did.)
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.El
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.It
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setting of
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.Va optopt
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for long options with
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.Va flag
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.No non- Ns Dv NULL :
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.Bl -tag -width "OpenBSD"
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.It GNU
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sets
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.Va optopt
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to
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.Va val .
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.It OpenBSD
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sets
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.Va optopt
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to 0 (since
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.Va val
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would never be returned).
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.El
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.It
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handling of
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.Ql -W
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with
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.Ql W;
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in the option string in
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.Xr getopt 3
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(not
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.Fn getopt_long ) :
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.Bl -tag -width "OpenBSD"
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.It GNU
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causes a segmentation fault.
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.It OpenBSD
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no special handling is done;
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.Ql W;
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is interpreted as two separate options, neither of which take an argument.
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.El
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.It
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setting of
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.Va optarg
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for long options without an argument that are invoked via
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.Ql -W
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(with
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.Ql W;
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in the option string):
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.Bl -tag -width "OpenBSD"
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.It GNU
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sets
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.Va optarg
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to the option name (the argument of
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.Ql -W ) .
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.It OpenBSD
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sets
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.Va optarg
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to
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.Dv NULL
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(the argument of the long option).
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.El
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.It
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handling of
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.Ql -W
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with an argument that is not (a prefix to) a known long option
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(with
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.Ql W;
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in the option string):
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.Bl -tag -width "OpenBSD"
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.It GNU
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returns
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.Ql -W
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with
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.Va optarg
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set to the unknown option.
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.It OpenBSD
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treats this as an error (unknown option) and returns
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.Ql \&?
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with
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.Va optopt
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set to 0 and
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.Va optarg
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set to
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.Dv NULL
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(as GNU's man page documents).
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.El
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.It
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The error messages are different.
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.It
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.Ox
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does not permute the argument vector at the same points in
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the calling sequence as GNU does.
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The aspects normally used by the caller
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(ordering after \-1 is returned, value of
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.Va optind
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relative to current positions) are the same, though.
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(We do fewer variable swaps.)
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.El
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.Sh ENVIRONMENT
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.Bl -tag -width Ev
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.It Ev POSIXLY_CORRECT
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If set, option processing stops when the first non-option is found and
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a leading
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.Sq +
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in the
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.Ar optstring
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is ignored.
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.El
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.Sh EXAMPLES
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.Bd -literal
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int bflag, ch, fd;
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int daggerset;
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/* options descriptor */
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static struct option longopts[] = {
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{ "buffy", no_argument, NULL, 'b' },
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{ "fluoride", required_argument, NULL, 'f' },
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{ "daggerset", no_argument, &daggerset, 1 },
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{ NULL, 0, NULL, 0 }
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};
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bflag = 0;
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while ((ch = getopt_long(argc, argv, "bf:", longopts, NULL)) != -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)) == -1)
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err(1, "unable to open %s", optarg);
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break;
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case 0:
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if (daggerset)
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fprintf(stderr, "Buffy will use her dagger to "
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"apply fluoride to dracula's teeth\en");
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break;
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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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.Ed
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.Sh SEE ALSO
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.Xr getopt 3
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.Sh HISTORY
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The
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.Fn getopt_long
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and
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.Fn getopt_long_only
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functions first appeared in GNU libiberty.
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This implementation first appeared in
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.Ox 3.3 .
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.Sh BUGS
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The
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.Ar argv
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argument is not really
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.Dv const
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as its elements may be permuted (unless
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.Ev POSIXLY_CORRECT
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is set).
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