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.\" ========================================================================
.\"
.IX Title "Getopt::Std 3perl"
.TH Getopt::Std 3perl "2021-09-24" "perl v5.32.1" "Perl Programmers Reference Guide"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH "NAME"
Getopt::Std \- Process single\-character switches with switch clustering
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 1
\&    use Getopt::Std;
\&
\&    getopts(\*(Aqoif:\*(Aq);  # \-o & \-i are boolean flags, \-f takes an argument
\&                      # Sets $opt_* as a side effect.
\&    getopts(\*(Aqoif:\*(Aq, \e%opts);  # options as above. Values in %opts
\&    getopt(\*(AqoDI\*(Aq);    # \-o, \-D & \-I take arg.
\&                      # Sets $opt_* as a side effect.
\&    getopt(\*(AqoDI\*(Aq, \e%opts);    # \-o, \-D & \-I take arg.  Values in %opts
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
The \f(CW\*(C`getopts()\*(C'\fR function processes single-character switches with switch
clustering.  Pass one argument which is a string containing all switches to be
recognized.  For each switch found, if an argument is expected and provided,
\&\f(CW\*(C`getopts()\*(C'\fR sets \f(CW$opt_x\fR (where \f(CW\*(C`x\*(C'\fR is the switch name) to the value of
the argument.  If an argument is expected but none is provided, \f(CW$opt_x\fR is
set to an undefined value.  If a switch does not take an argument, \f(CW$opt_x\fR
is set to \f(CW1\fR.
.PP
Switches which take an argument don't care whether there is a space between
the switch and the argument.  If unspecified switches are found on the
command-line, the user will be warned that an unknown option was given.
.PP
The \f(CW\*(C`getopts()\*(C'\fR function returns true unless an invalid option was found.
.PP
The \f(CW\*(C`getopt()\*(C'\fR function is similar, but its argument is a string containing
all switches that take an argument.  If no argument is provided for a switch,
say, \f(CW\*(C`y\*(C'\fR, the corresponding \f(CW$opt_y\fR will be set to an undefined value.
Unspecified switches are silently accepted.  Use of \f(CW\*(C`getopt()\*(C'\fR is not
recommended.
.PP
Note that, if your code is running under the recommended \f(CW\*(C`use strict
vars\*(C'\fR pragma, you will need to declare these package variables
with \f(CW\*(C`our\*(C'\fR:
.PP
.Vb 1
\&    our($opt_x, $opt_y);
.Ve
.PP
For those of you who don't like additional global variables being created,
\&\f(CW\*(C`getopt()\*(C'\fR and \f(CW\*(C`getopts()\*(C'\fR will also accept a hash reference as an optional
second argument.  Hash keys will be \f(CW\*(C`x\*(C'\fR (where \f(CW\*(C`x\*(C'\fR is the switch name) with
key values the value of the argument or \f(CW1\fR if no argument is specified.
.PP
To allow programs to process arguments that look like switches, but aren't,
both functions will stop processing switches when they see the argument
\&\f(CW\*(C`\-\-\*(C'\fR.  The \f(CW\*(C`\-\-\*(C'\fR will be removed from \f(CW@ARGV\fR.
.ie n .SH """\-\-help"" and ""\-\-version"""
.el .SH "\f(CW\-\-help\fP and \f(CW\-\-version\fP"
.IX Header "--help and --version"
If \f(CW\*(C`\-\*(C'\fR is not a recognized switch letter, \fBgetopts()\fR supports arguments
\&\f(CW\*(C`\-\-help\*(C'\fR and \f(CW\*(C`\-\-version\*(C'\fR.  If \f(CW\*(C`main::HELP_MESSAGE()\*(C'\fR and/or
\&\f(CW\*(C`main::VERSION_MESSAGE()\*(C'\fR are defined, they are called; the arguments are
the output file handle, the name of option-processing package, its version,
and the switches string.  If the subroutines are not defined, an attempt is
made to generate intelligent messages; for best results, define \f(CW$main::VERSION\fR.
.PP
If embedded documentation (in pod format, see perlpod) is detected
in the script, \f(CW\*(C`\-\-help\*(C'\fR will also show how to access the documentation.
.PP
Note that due to excessive paranoia, if \f(CW$Getopt::Std::STANDARD_HELP_VERSION\fR
isn't true (the default is false), then the messages are printed on \s-1STDERR,\s0
and the processing continues after the messages are printed.  This being
the opposite of the standard-conforming behaviour, it is strongly recommended
to set \f(CW$Getopt::Std::STANDARD_HELP_VERSION\fR to true.
.PP
One can change the output file handle of the messages by setting
\&\f(CW$Getopt::Std::OUTPUT_HELP_VERSION\fR.  One can print the messages of \f(CW\*(C`\-\-help\*(C'\fR
(without the \f(CW\*(C`Usage:\*(C'\fR line) and \f(CW\*(C`\-\-version\*(C'\fR by calling functions \fBhelp_mess()\fR
and \fBversion_mess()\fR with the switches string as an argument.