Getopt::Euclid(3p)

NAME
Getopt::Euclid - Executable Uniform Command-Line Interface Descriptions

VERSION
This document describes Getopt::Euclid version 0.4.5

SYNOPSIS
    use Getopt::Euclid;

    if ($ARGV{-i}) {
        print "Interactive mode...\n";
    }

    for my $x (0..$ARGV{-size}{h}-1) {
        for my $y (0..$ARGV{-size}{w}-1) {
            do_something_with($x, $y);
        }
    }

    __END__

    =head1 NAME

    yourprog - Your program here

    =head1 VERSION

    This documentation refers to yourprog version 1.9.4

    =head1 USAGE

        yourprog [options]  -s[ize]=<h>x<w>  -o[ut][file] <file>

    =head1 REQUIRED ARGUMENTS

    =over

    =item  -s[ize]=<h>x<w>

    Specify size of simulation

    =for Euclid:
        h.type:    int > 0
        h.default: 24
        w.type:    int >= 10
        w.default: 80

    =item  -o[ut][file] <file>

    Specify output file

    =for Euclid:
        file.type:    writable
        file.default: '-'

    =back

    =head1 OPTIONS

    =over

    =item  -i

    Specify interactive simulation

    =item  -l[[en][gth]] <l>

    Length of simulation. The default is l.default

    =for Euclid:
        l.type:    int > 0
        l.default: 99

    =item --debug [<log_level>]

    Set the log level. Default is log_level.default but if you provide --debug,
    then it is log_level.opt_default.

    =for Euclid:
        log_level.type:        int
        log_level.default:     0
        log_level.opt_default: 1

    =item --version

    =item --usage

    =item --help

    =item --man

    Print the usual program information

    =back

    Remainder of documentation starts here...

    =head1 AUTHOR

    Damian Conway (DCONWAY@CPAN.org)

    =head1 BUGS

    There are undoubtedly serious bugs lurking somewhere in this code.
    Bug reports and other feedback are most welcome.

    =head1 COPYRIGHT

    Copyright (c) 2005, Damian Conway. All Rights Reserved.
    This module is free software. It may be used, redistributed
    and/or modified under the terms of the Perl Artistic License
    (see http://www.perl.com/perl/misc/Artistic.html)

DESCRIPTION
Getopt::Euclid uses your program's own POD documentation to create a powerful command-line argument parser. This ensures that your program's documented interface and its actual interface always agree.

The created command-line argument parser includes many features such as argument type checking, required arguments, exclusive arguments, optional arguments with default values, automatic usage message, ...

To use the module, simply write the following at the top of your program:

    use Getopt::Euclid;

This will cause Getopt::Euclid to be require'd and its import method will be called. It is important that the import method be allowed to run, so do not invoke Getopt::Euclid in the following manner:

    # Will not work
    use Getopt::Euclid ();

When the module is loaded within a regular Perl program, it will:

1.  locate any POD in the same *.pl file or its associated *.pod file.

2.  extract information from that POD, most especially from the "=head1 REQUIRED ARGUMENTS" and "=head1 OPTIONS" sections,

3.  build a parser that parses the arguments and options the POD specifies,

4.  remove the command-line arguments from @ARGV and parse them, and

5.  put the results in the global %ARGV variable (or into specifically named optional variables, if you request that -- see "Exporting option variables").

As a special case, if the module is loaded within some other module (i.e. from within a ".pm" file), it still locates and extracts POD information, but instead of parsing @ARGV immediately, it caches that information and installs an import() subroutine in the caller module. This new import() acts just like Getopt::Euclid's own import, except that it adds the POD from the caller module to the POD of the callee.

All of which just means you can put some or all of your CLI specification in a module, rather than in the application's source file. See "Module interface" for more details.

INTERFACE

  Program interface
You write:

    use Getopt::Euclid;

and your command-line is parsed automagically.

  Module interface

import()
    You write:

        use Getopt::Euclid;

    and your module will then act just like Getopt::Euclid (i.e. you can use your module instead of Getopt::Euclid>, except that your module's POD will also be prepended to the POD of any module that loads yours. In other words, you can use Getopt::Euclid in a module to create a standard set of CLI arguments, which can then be added to any application simply by loading your module.

    To accomplish this trick Getopt::Euclid installs an import() subroutine in your module. If your module already has an import() subroutine defined, terrible things happen. So do not do that.

    You may also short-circuit the import method within your calling program to have the POD from several modules included for argument parsing.

        use Module1::Getopt (); # No argument parsing
        use Module2::Getopt (); # No argument parsing
        use Getopt::Euclid;     # Arguments parsed

process_args()
    Alternatively, to parse arguments from a source different from @ARGV, use the process_args() subroutine.

        use Getopt::Euclid qw(:defer);
        my @args = ( '-in', 'file.txt', '-out', 'results.txt' );
        Getopt::Euclid->process_args(\@args);

    If you want to use the :minimal or :vars mode in this type of scenario, you can pass extra options to process_args():

        use Getopt::Euclid qw(:defer);
        my @args = ( '-in', 'file.txt', '-out', 'results.txt' );
        Getopt::Euclid->process_args(\@args, {-minimal => 1, -vars => 'prefix_'});

    This is particularly when you plan on processing POD manually.

process_pods()
    Similarly, to parse argument specifications from a source different than the current script (and its dependencies), use the process_pods() subroutine.

        use Getopt::Euclid ();
        my @pods = ( 'script.pl', 'Module.pm' );
        $Getopt::Euclid::MAN = Getopt::Euclid->process_pods(\@pods, {-strict => 1});
        my @args = ( '-in', 'file.txt', '-out', 'results.txt' );
        Getopt::Euclid->process_args(\@args);

    By default, this method will look for .pod files associated with the given .pl and .pm files and use these .pod files preferentially when available. Set -strict to 1 to only use the given files.

  POD interface
This is where all the action is. POD markup can be placed in a .pod file that has the same prefix as the corresponding Perl file. Alternatively, POD can be inserted anywhere in the Perl code, but is typically added either after an __END__ statement (like in the SYNOPSIS), or interspersed in the code:

    use Getopt::Euclid;

    =head1 NAME

    yourprog - Your program here

    =head1 REQUIRED ARGUMENTS

    =over

    =item  -s[ize]=<h>x<w>

    Specify size of simulation

    =for Euclid:
        h.type:    int > 0
        h.default: 24
        w.type:    int >= 10
        w.default: 80

    =back

    =head1 OPTIONS

    =over

    =item  -i

    Specify interactive simulation

    =back

    =cut

    # Getopt::Euclid has parsed commandline parameters and stored them in %ARGV

    if ($ARGV{-i}) {
        print "Interactive mode...\n";
    }

    for my $x (0..$ARGV{-size}{h}-1) {
        for my $y (0..$ARGV{-size}{w}-1) {
            do_something_with($x, $y);
        }
    }

When Getopt::Euclid is loaded in a non-".pm" file, it searches that file for the following POD documentation:

=head1 NAME
    Getopt::Euclid ignores the name specified here. In fact, if you use the standard "--help", "--usage", "--man", "--podfile", or "--version" arguments (see "Standard arguments"), the module replaces the name specified in this POD section with the actual name by which the program was invoked (i.e. with $0).

=head1 USAGE
    Getopt::Euclid ignores the usage line specified here. If you use the standard "--help", "--usage", "--man" or "--podfile" arguments, the module replaces the usage line specified in this POD section with a usage line that reflects the actual interface that the module has constructed.

=head1 VERSION
    Getopt::Euclid extracts the current version number from this POD section. To do that it simply takes the first substring that matches <digit>.<digit> or <digit>_<digit>. It also accepts one or more additional trailing .<digit> or _<digit>, allowing for multi-level and "alpha" version numbers such as:

        =head1 VERSION

        This is version 1.2.3

    or:

        =head1 VERSION

        This is alpha release 1.2_34

    You may also specify the version number in your code. However, in order for Getopt::Euclid to properly read it, it must be in a "BEGIN" block:

        BEGIN { use version; our $VERSION = qv('1.2.3') }
        use Getopt::Euclid;

    Euclid stores the version as $Getopt::Euclid::SCRIPT_VERSION.

=head1 REQUIRED ARGUMENTS
    Getopt::Euclid uses the specifications in this POD section to build a parser for command-line arguments. That parser requires that every one of the specified arguments is present in any command-line invocation. See "Specifying arguments" for details of the specification syntax.

    The actual headings that Getopt::Euclid can recognize here are:

        =head1 [STANDARD|STD|PROGRAM|SCRIPT|CLI|COMMAND[-| ]LINE] [REQUIRED|MANDATORY] [PARAM|PARAMETER|ARG|ARGUMENT][S]

    Caveat: Do not put additional subheadings (=headX) inside the REQUIRED ARGUMENTS section.

=head1 OPTIONS
    Getopt::Euclid uses the specifications in this POD section to build a parser for command-line arguments. That parser does not require that any of the specified arguments is actually present in a command-line invocation. Again, see "Specifying arguments" for details of the specification syntax.

    Typically a program will specify both "REQUIRED ARGUMENTS" and "OPTIONS", but there is no requirement that it supply both, or either.

    The actual headings that Getopt::Euclid recognizes here are:

        =head1 [STANDARD|STD|PROGRAM|SCRIPT|CLI|COMMAND[-| ]LINE] OPTION[AL|S] [PARAM|PARAMETER|ARG|ARGUMENT][S]

    Caveat: Do not put additional subheadings (=headX) inside the REQUIRED ARGUMENTS section.

=head1 COPYRIGHT
    Getopt::Euclid prints this section whenever the standard "--version" option is specified on the command-line.

    The actual heading that Getopt::Euclid recognizes here is any heading containing any of the words "COPYRIGHT", "LICENCE", or "LICENSE".

  Specifying arguments
Each required or optional argument is specified in the POD in the following format:

    =item ARGUMENT_STRUCTURE

    ARGUMENT_DESCRIPTION

    =for Euclid:
        ARGUMENT_OPTIONS
        PLACEHOLDER_CONSTRAINTS

Argument structure

•   Each argument is specified as an "=item".

•   Any part(s) of the specification that appear in square brackets are treated as optional.

•   Any parts that appear in angle brackets are placeholders for actual values that must be specified on the command-line.

•   Any placeholder that is immediately followed by "..." may be repeated as many times as desired.

•   Any whitespace in the structure specifies that any amount of whitespace (including none) is allowed at the same position on the command-line.

•   A vertical bar indicates the start of an alternative variant of the argument.

For example, the argument specification:

    =item -i[n] [=] <file> | --from <file>

indicates that any of the following may appear on the command-line:

    -idata.txt    -i data.txt    -i=data.txt    -i = data.txt

    -indata.txt   -in data.txt   -in=data.txt   -in = data.txt

    --from data.text

as well as any other combination of whitespacing.

Any of the above variations would cause all three of:

    $ARGV{'-i'}
    $ARGV{'-in'}
    $ARGV{'--from'}

to be set to the string 'data.txt'.

You could allow the optional "=" to also be an optional colon by specifying:

    =item -i[n] [=|:] <file>

Optional components may also be nested, so you could write:

    =item -i[n[put]] [=] <file>

which would allow "-i", "-in", and "-input" as synonyms for this argument and would set all three of $ARGV{'-i'}, $ARGV{'-in'}, and $ARGV{'-input'} to the supplied file name.

The point of setting every possible variant within %ARGV is that this allows you to use a single key (say $ARGV{'-input'}, regardless of how the argument is actually specified on the command-line.

  Repeatable arguments
Normally Getopt::Euclid only accepts each specified argument once, the first time it appears in @ARGV. However, you can specify that an argument may appear more than once, using the "repeatable" option:

    =item file=<filename>

    =for Euclid:
        repeatable

When an argument is marked repeatable the corresponding entry of %ARGV will not contain a single value, but rather an array reference. If the argument also has "Multiple placeholders", then the corresponding entry in %ARGV will be an array reference with each array entry being a hash reference.

  Boolean arguments
If an argument has no placeholders it is treated as a boolean switch and its entry in %ARGV will be true if the argument appeared in @ARGV.

For a boolean argument, you can also specify variations that are false, if they appear. For example, a common idiom is:

    =item --print

    Print results

    =item --noprint

    Do not print results

These two arguments are effectively the same argument, just with opposite boolean values. However, as specified above, only one of $ARGV{'--print'} and $ARGV{'--noprint'} will be set.

As an alternative you can specify a single argument that accepts either value and sets both appropriately:

    =item --[no]print

    [Do not] print results

    =for Euclid:
        false: --noprint

With this specification, if "--print" appears in @ARGV, then $ARGV{'--print'} will be true and $ARGV{'--noprint'} will be false. On the other hand, if "--noprint" appears in @ARGV, then $ARGV{'--print'} will be false and $ARGV{'--noprint'} will be true.

The specified false values can follow any convention you wish:

    =item [+|-]print

    =for Euclid:
        false: -print

or:

    =item -report[_no[t]]

    =for Euclid:
        false: -report_no[t]

et cetera.

  Multiple placeholders
An argument can have two or more placeholders:

    =item -size <h> <w>

The corresponding command line argument would then have to provide two values:

    -size 24 80

Multiple placeholders can optionally be separated by literal characters (which must then appear on the command-line). For example:

    =item -size <h>x<w>

would then require a command-line of the form:

    -size 24x80

If an argument has two or more placeholders, the corresponding entry in %ARGV becomes a hash reference, with each of the placeholder names as one key. That is, the above command-line would set both "$ARGV{'-size'}{'h'}" and "$ARGV{'-size'}{'w'}".

  Optional placeholders
Placeholders can be specified as optional as well:

    =item -size <h> [<w>]

This specification then allows either:

    -size 24

or:

    -size 24 80

on the command-line. If the second placeholder value is not provided, the corresponding "$ARGV{'-size'}{'w'}" entry is set to "undef". See also "Placeholder defaults".

  Unflagged placeholders
If an argument consists of a single placeholder with no "flag" marking it:

    =item <filename>

then the corresponding entry in %ARG will have a key the same as the placeholder (including the surrounding angle brackets):

    if ($ARGV{'<filename>'} eq '-') {
        $fh = \*STDIN;
    }

The same is true for any more-complicated arguments that begin with a placeholder:

    =item <h> [x <w>]

The only difference in the more-complex cases is that, if the argument has any additional placeholders, the entire entry in %ARGV becomes a hash:

    my $total_size
        = $ARGV{'<h>'}{'h'} * $ARGV{'<h>'}{'w'}

Note that, as in earlier multi-placeholder examples, the individual second- level placeholder keys do not retain their angle-brackets.

  Repeated placeholders
Any placeholder that is immediately followed by "...", like so:

    =item -lib <file>...

    =for Euclid:
        file.type: readable

will match at least once, but as many times as possible before encountering the next argument on the command-line. This allows one to specify multiple values for an argument, for example:

    -lib file1.txt file2.txt

An unconstrained repeated unflagged placeholder (see "Placeholder constraints" and "Unflagged placeholders") will consume the rest of the command-line, and so should be specified last in the POD

    =item -n <name>

    =item <offset>...

    =for Euclid:
        offset.type: 0+int

and on the command-line:

    -n foobar 1 5 0 23

If a placeholder is repeated, the corresponding entry in %ARGV will then be an array reference, with each individual placeholder match in a separate element. For example:

    for my $lib (@{ $ARGV{'-lib'} }) {
        add_lib($lib);
    }

    warn "First offset is: $ARGV{'<offsets>'}[0]";
    my $first_offset = shift @{ $ARGV{'<offsets>'} };

  Placeholder constraints
You can specify that the value provided for a particular placeholder must satisfy a particular set of restrictions by using a "=for Euclid" block. For example:

    =item -size <h>x<w>

    =for Euclid:
        h.type: integer
        w.type: integer

specifies that both the "<h>" and "<w>" must be given integers. You can also specify an operator expression after the type name:

    =for Euclid:
        h.type: integer > 0
        w.type: number <= 100

specifies that "<h>" has to be given an integer that is greater than zero, and that "<w>" has to be given a number (not necessarily an integer) that is no more than 100.

These type constraints have two alternative syntaxes:

    PLACEHOLDER.type: TYPE BINARY_OPERATOR EXPRESSION

as shown above, and the more general:

    PLACEHOLDER.type: TYPE [, EXPRESSION_INVOLVING(PLACEHOLDER)]

Using the second syntax, you could write the previous constraints as:

    =for Euclid:
        h.type: integer, h > 0
        w.type: number,  w <= 100

In other words, the first syntax is just sugar for the most common case of the second syntax. The expression can be as complex as you wish and can refer to the placeholder as many times as necessary:

    =for Euclid:
        h.type: integer, h > 0 && h < 100
        w.type: number,  Math::is_prime(w) || w % 2 == 0

Note that the expressions are evaluated in the "package main" namespace, so it is important to qualify any subroutines that are not in that namespace. Furthermore, any subroutines used must be defined (or loaded from a module) before the "use Getopt::Euclid" statement.

You can also use constraints that involve variables. You must use the :defer mode and the variables must be globally accessible:

    use Getopt::Euclid qw(:defer);
    our $MIN_VAL = 100;
    Getopt::Euclid->process_args(\@ARGV);

    __END__

    =head1 OPTIONS

    =over

    =item --magnitude <magnitude>

    =for Euclid
       magnitude.type: number, magnitude > $MIN_VAL

    =back

  Standard placeholder types
Getopt::Euclid recognizes the following standard placeholder types:

    Name            Placeholder value...        Synonyms
    ============    ====================        ================

    integer         ...must be an integer       int    i

    +integer        ...must be a positive       +int   +i
                    integer
                    (same as: integer > 0)

    0+integer       ...must be a positive       0+int  0+i
                    integer or zero
                    (same as: integer >= 0)

    number          ...must be an number        num    n

    +number         ...must be a positive       +num   +n
                    number
                    (same as: number > 0)

    0+number        ...must be a positive       0+num  0+n
                    number or zero
                    (same as: number >= 0)

    string          ...may be any string        str    s
                    (default type)

    readable        ...must be the name         input  in
                    of a readable file

    writeable       ...must be the name         writable output out
                    of a writeable file
                    (or of a non-existent
                    file in a writeable
                    directory)

    /<regex>/       ...must be a string
                    matching the specified
                    pattern

Since regular expressions are supported, you can easily match many more type of strings for placeholders by using the regular expressions available in Regexp::Common. If you do that, you may want to also use custom placeholder error messages (see "Placeholder type errors") since the messages would otherwise not be very informative to users.

    use Regexp::Common qw /zip/;
    use Getopt::Euclid;

    ...

    =item -p <postcode>

    Enter your postcode here

    =for Euclid:
        postcode.type:  /$RE{zip}{France}/
        postcode.type.error: <postcode> must be a valid ZIP code

  Placeholder type errors
If a command-line argument's placeholder value does not satisify the specified type, an error message is automatically generated. However, you can provide your own message instead, using the ".type.error" specifier:

    =for Euclid:
        h.type:        integer, h > 0 && h < 100
        h.type.error:  <h> must be between 0 and 100 (not h)

        w.type:        number,  Math::is_prime(w) || w % 2 == 0
        w.type.error:  Cannot use w for <w> (must be an even prime number)

Whenever an explicit error message is provided, any occurrence within the message of the placeholder's unbracketed name is replaced by the placeholder's value (just as in the type test itself).

  Placeholder defaults
You can also specify a default value for any placeholders that are not given values on the command-line (either because their argument is not provided at all, or because the placeholder is optional within the argument). For example:

    =item -size <h>[x<w>]

    Set the size of the simulation

    =for Euclid:
        h.default: 24
        w.default: 80

This ensures that if no "<w>" value is supplied:

    -size 20

then "$ARGV{'-size'}{'w'}" is set to 80. Likewise, of the "-size" argument is omitted entirely, both "$ARGV{'-size'}{'h'}" and "$ARGV{'-size'}{'w'}" are set to their respective default values

However, Getopt::Euclid also supports a second type of default, optional defaults, that apply only to flagged, optional placeholders.

For example:

    =item --debug [<log_level>]

    Set the log level

    =for Euclid:
        log_level.type:        int
        log_level.default:     0
        log_level.opt_default: 1

This ensures that if the option "--debug" is not specified, then $ARGV{'--debug'} is set to 0, the regular default. But if no "<log_level>" value is supplied:

    --debug

then $ARGV{'--debug'} is set to 1, the optional default.

The default value can be any valid Perl compile-time expression:

    =item -pi=<pi value>

    =for Euclid:
        pi value.default: atan2(0,-1)

You can refer to an argument default or optional default value in its POD entry as shown below:

    =item -size <h>[x<w>]

    Set the size of the simulation [default: h.default x w.default]

    =for Euclid:
        h.default: 24
        w.default: 80

    =item --debug <level>

    Set the debug level. The default is level.default if you supply --debug but
    omit a <level> value.

    =for Euclid:
        level.opt_default: 3

Just like for "Placeholder constraints", you can also use variables to define default values. You must use the :defer mode and the variables must be globally accessible:

    use Getopt::Euclid qw(:defer);
    Getopt::Euclid->process_args(\@ARGV);

    __END__

    =head1 OPTIONS

    =over

    =item --home <home>

    Your project home. When omitted, this defaults to the location stored in
    the HOME environment variable.

    =for Euclid
       home.default: $ENV{'HOME'}

    =back

  Exclusive placeholders
Some arguments can be mutually exclusive. In this case, it is possible to specify that a placeholder excludes a list of other placeholders, for example:

    =item -height <h>

    Set the desired height

    =item -width <w>

    Set the desired width

    =item -volume <v>

    Set the desired volume

    =for Euclid:
        v.excludes: h, w
        v.excludes.error: Either set the volume or the height and weight

Specifying both placeholders at the same time on the command-line will generate an error. Note that the error message can be customized, as illustrated above.

When using exclusive arguments that have default values, the default value of the placeholder with the .excludes statement has precedence over any other placeholders.

  Argument cuddling
Getopt::Euclid allows any "flag" argument to be "cuddled". A flag argument consists of a single non- alphanumeric character, followed by a single alpha-numeric character:

    =item -v

    =item -x

    =item +1

    =item =z

Cuddling means that two or more such arguments can be concatenated after a single common non-alphanumeric. For example:

    -vx

Note, however, that only flags with the same leading non-alphanumeric can be cuddled together. Getopt::Euclid would not allow:

    -vxz

This is because cuddling is recognized by progressively removing the second character of the cuddle. In other words:

    -vxz

becomes:

    -v -xz

which becomes:

    -v -x z

which will fail, unless a "z" argument has also been specified.

On the other hand, if the argument:

    =item -e <cmd>

had been specified, the module would accept:

    -vxe'print time'

as a cuddled version of:

    -v -x -e'print time'

  Exporting option variables
By default, the module only stores arguments into the global %ARGV hash. You can request that options are exported as variables into the calling package using the special ':vars' specifier:

    use Getopt::Euclid qw( :vars );

That is, if your program accepts the following arguments:

    -v
    --mode <modename>
    <infile>
    <outfile>
    --auto-fudge <factor>      (repeatable)
    --also <a>...
    --size <w>x<h>
    --multiply <num1>x<num2>   (repeatable)

Then these variables will be exported

    $ARGV_v
    $ARGV_mode
    $ARGV_infile
    $ARGV_outfile
    @ARGV_auto_fudge
    @ARGV_also
    %ARGV_size          # With entries $ARGV_size{w} and $ARGV_size{h}
    @ARGV_multiply      # With entries that are hashref similar to \%ARGV_size

For options that have multiple variants, only the longest variant is exported.

The type of variable exported (scalar, hash, or array) is determined by the type of the corresponding value in %ARGV. Command-line flags and arguments that take single values will produce scalars, arguments that take multiple values will produce hashes, and repeatable arguments will produce arrays.

If you do not like the default prefix of "ARGV_", you can specify your own, such as "opt_", like this:

    use Getopt::Euclid qw( :vars<opt_> );

The major advantage of using exported variables is that any misspelling of argument variables in your code will be caught at compile-time by "use strict".

  Standard arguments
Getopt::Euclid automatically provides four standard arguments to any program that uses the module. The behaviours of these arguments are "hard- wired" and cannot be changed, not even by defining your own arguments of the same name.

The standard arguments are:

--usage  usage()
    The --usage argument causes the program to print a short usage summary and exit. The "Getopt::Euclid-"usage()> subroutine provides access to the string of this message.

--help  help()
    The --help argument causes the program to take a longer usage summary (with a full list of required and optional arguments) provided in POD format by help(), convert it to plaintext, display it and exit. The message is paged using IO::Pager::Page (or IO::Page) if possible.

--man  man()
    The --man argument causes the program to take the POD documentation for the program, provided by man(), convert it to plaintext, display it and exit. The message is paged using IO::Pager::Page (or IO::Page) if possible.

--podfile  podfile()
    The --podfile argument is provided for authors. It causes the program to take the POD manual from man(), write it in a .pod file with the same base name as the program, display the name of the output file and exit. These actions can also be executed by calling the podfile() subroutine.This argument is not really a standard argument, but it is useful if the program's POD is to be passed to a POD converter because, among other things, any default value specified is interpolated and replaced by its value in the .pod file, contrary to in the program's .pl file.

    If you want to automate the creation of a POD file during the build process, you can edit you Makefile.PL or Build.PL file and add these lines:

       my @args = ($^X, '-Ilib', '/path/to/script', '--podfile');
       system(@args) == 0 or die "System call to '@args' failed:\n$?\n";

    If you use Module::Install to bundle your script, you might be interested in using Module::Install::PodFromEuclid to include the --podfile step into the installation process.

--version  version()
    The --version argument causes the program to print the version number of the program (as specified in the "=head1 VERSION" section of the POD) and any copyright information (as specified in the "=head1 COPYRIGHT" POD section) and then exit. The "Getopt::Euclid-"version()> subroutine provides access to the string of this message.

  Minimalist keys
By default, the keys of %ARGV will match the program's interface exactly. That is, if your program accepts the following arguments:

    -v
    --mode <modename>
    <infile>
    <outfile>
    --auto-fudge

Then the keys that appear in %ARGV will be:

    '-v'
    '--mode'
    '<infile>'
    '<outfile>'
    '--auto-fudge'

In some cases, however, it may be preferable to have Getopt::Euclid set up those hash keys without "decorations". That is, to have the keys of %ARGV be simply:

    'v'
    'mode'
    'infile'
    'outfile'
    'auto_fudge'

You can arrange this by loading the module with the special ':minimal_keys' specifier:

    use Getopt::Euclid qw( :minimal_keys );

Note that, in rare cases, using this mode may cause you to lose data (for example, if the interface specifies both a "--step" and a "<step>" option). The module throws an exception if this happens.

  Deferring argument parsing
In some instances, you may want to avoid the parsing of arguments to take place as soon as your program is executed and Getopt::Euclid is loaded. For example, you may need to examine @ARGV before it is processed (and emptied) by Getopt::Euclid. Or you may intend to pass your own arguments manually only using process_args().

To defer the parsing of arguments, use the specifier ':defer':

    use Getopt::Euclid qw( :defer );
    # Do something...
    Getopt::Euclid->process_args(\@ARGV);

DIAGNOSTICS

  Compile-time diagnostics
The following diagnostics are mainly caused by problems in the POD specification of the command-line interface:

Getopt::Euclid was unable to access POD
    Something is horribly wrong. Getopt::Euclid was unable to read your program to extract the POD from it. Check your program's permissions, though it is a mystery how perl was able to run the program in the first place, if it is not readable.

.pm file cannot define an explicit import() when using Getopt::Euclid
    You tried to define an import() subroutine in a module that was also using Getopt::Euclid. Since the whole point of using Getopt::Euclid in a module is to have it build an import() for you, supplying your own import() as well defeats the purpose.

Unknown specification: %s
    You specified something in a "=for Euclid" section that Getopt::Euclid did not understand. This is often caused by typos, or by reversing a placeholder.type or placeholder.default specification (that is, writing type.placeholder or default.placeholder instead).

Unknown type (%s) in specification: %s
Unknown .type constraint: %s
    Both these errors mean that you specified a type constraint that Getopt::Euclid did not recognize. This may have been a typo:

        =for Euclid
            count.type: inetger

    or else the module simply does not know about the type you specified:

        =for Euclid
            count.type: complex

    See "Standard placeholder types" for a list of types that Getopt::Euclid does recognize.

Invalid .type constraint: %s
    You specified a type constraint that is not valid Perl. For example:

        =for Euclid
            max.type: integer not equals 0

    instead of:

        =for Euclid
            max.type: integer != 0

Invalid .default value: %s
    You specified a default value that is not valid Perl. For example:

        =for Euclid
            curse.default: *$@!&

    instead of:

        =for Euclid
            curse.default: '*$@!&'

Invalid .opt_default value: %s
    Same as previous diagnostic, but for optional defaults.

Invalid reference to field %s.default in argument description: %s
    You referred to a default value in the description of an argument, but there is no such default. It may be a typo, or you may be referring to the default value for a different argument, e.g.:

        =item -a <age>

        An optional age. Default: years.default

        =for Euclid
            age.default: 21

    instead of:

        =item -a <age>

        An optional age. Default: age.default

        =for Euclid
            age.default: 21

Invalid reference to field %s.opt_default in argument description: %s
    Same as previous diagnostic, but for optional defaults.

Invalid .opt_default constraint: Placeholder <%s> must be optional
    You specified an optional default but the placeholder that it affects is not an optional placeholder. For example:

        =item  -l[[en][gth]] <l>

        =for Euclid:
            l.opt_default: 123

    instead of:

        =item  -l[[en][gth]] [<l>]

        =for Euclid:
            l.opt_default: 123

Invalid .opt_default constraint: Parameter %s must have a flag
    You specified an optional default but the parameter that it affects is unflagged. For example:

        =item  <length>

        =for Euclid:
            l.opt_default: 123

    instead of:

        =item  -l [<length>]

        =for Euclid:
            l.opt_default: 123

Invalid .excludes value for variable %s: <%s> does not exist
    You specified to exclude a variable that was not seen in the POD. Make sure that this is not a typo.

Invalid constraint: %s (No <%s> placeholder in argument: %s)
    You attempted to define a ".type" constraint for a placeholder that did not exist. Typically this is the result of the misspelling of a placeholder name:

        =item -foo <bar>

        =for Euclid:
            baz.type: integer

    or a "=for Euclid:" that has drifted away from its argument:

        =item -foo <bar>

        =item -verbose

        =for Euclid:
            bar.type: integer

Getopt::Euclid loaded a second time
    You tried to load the module twice in the same program. Getopt::Euclid does not work that way. Load it only once.

Unknown mode ('%s')
    The only argument that a "use Getopt::Euclid" command accepts is ':minimal_keys' (see "Minimalist keys"). You specified something else instead (or possibly forgot to put a semicolon after "use Getopt::Euclid").

Internal error: minimalist mode caused arguments '%s' and '%s' to clash
    Minimalist mode removes certain characters from the keys hat are returned in %ARGV. This can mean that two command-line options (such as "--step" and "<step>") map to the same key (i.e. 'step'). This in turn means that one of the two options has overwritten the other within the %ARGV hash. The program developer should either turn off ':minimal_keys' mode within the program, or else change the name of one of the options so that the two no longer clash.

  Run-time diagnostics
The following diagnostics are caused by problems in parsing the command-line

Missing required argument(s): %s
    At least one argument specified in the "REQUIRED ARGUMENTS" POD section was not present on the command-line.

Invalid %s argument. %s must be %s but the supplied value (%s) is not.
    Getopt::Euclid recognized the argument you were trying to specify on the command-line, but the value you gave to one of that argument's placeholders was of the wrong type.

Unknown argument: %s
    Getopt::Euclid did not recognize an argument you were trying to specify on the command-line. This is often caused by command-line typos or an incomplete interface specification.

CONFIGURATION AND ENVIRONMENT
Getopt::Euclid requires no configuration files or environment variables.

DEPENDENCIES

•   version

•   Pod::Select

•   Pod::PlainText

•   File::Basename

•   File::Spec::Functions

•   List::Util

•   Text::Balanced

•   IO::Pager::Page (recommended)

INCOMPATIBILITIES
Getopt::Euclid may not work properly with POD in Perl files that have been converted into an executable with PerlApp or similar software. A possible workaround may be to move the POD to a __DATA__ section or a separate .pod file.

BUGS AND LIMITATIONS
Please report any bugs or feature requests via GitHub issues <https://github.com/bigpresh/Getopt-Euclid/issues>

Pull requests to fix bugs / add features welcome!

GitHub repo <https://github.com/bigpresh/Getopt-Euclid>

"git clone git@github.com:bigpresh/Getopt-Euclid.git"

The RT queue <https://rt.cpan.org/Public/Dist/Display.html?Name=Getopt-Euclid> still exists but GitHub issues are preferred due to their integration with pull requests etc.

AUTHOR
Damian Conway "<DCONWAY@cpan.org>"

Florent Angly "<florent.angly@gmail.com>"

David Precious (BIGPRESH) "<davidp@preshweb.co.uk>"

LICENCE AND COPYRIGHT
Copyright (c) 2005, Damian Conway "<DCONWAY@cpan.org>". All rights reserved.

This module is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

DISCLAIMER OF WARRANTY
BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE SOFTWARE "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE SOFTWARE IS WITH YOU. SHOULD THE SOFTWARE PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR, OR CORRECTION.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE SOFTWARE AS PERMITTED BY THE ABOVE LICENCE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE SOFTWARE (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE SOFTWARE TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.