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** Getopt::Long
[[http://search.cpan.org/perldoc?Getopt::Long][Getopt::long]] is a
useful module to parse command line arguements.
A basic usage is something like this:
#+BEGIN_SRC perl
#!/usr/bin/perl -w
use strict;
use YAML::Syck;
use Getopt::Long;
GetOptions('config=s' => \my $cfg_file,);
my $config = LoadFile $cfg_file
#+END_SRC
In *GetOptions*, we require a value for config with *config=s*. If we
wante an integer, we replace 's' with 'i', and for a floating point,
with 'f'.
Call your script :
#+BEGIN_EXAMPLE
% script.pl --config=file.yml #this one works
% script.pl --config file.yml #this one too!
% script.pl -c file.yml #and this one too
#+END_EXAMPLE
The three syntaxes are understood.
A good practices is to combine this module with
[[http://search.cpan.org/perldoc?Pod::Usage][Pod::Usage]]. Let's do some
modifications on the example:
#+BEGIN_SRC perl
#!/usr/bin/perl -w
use strict;
use YAML::Syck;
use Getopt::Long;
use Pod::Usage;
GetOptions('config=s' => \my $cfg_file,) or pod2usage(2);
pod2usage(2) unless @ARGV > 0;
my $config = LoadFile $cfg_file
__END__
=head1 NAME
uberscript
=head1 SYNOPSIS
uberscript [options]
Options:
--config config file
=head1 Options
=over 4
=item B<config>
Path to the config file
#+END_SRC
then
#+BEGIN_EXAMPLE
% perl uberscript
Usage:
uberscript [options]
Options:
--config config file
#+END_EXAMPLE
From now if we call our script without argument, the POD will be printed
on STDIN.
** MooseX::Getopt
[[http://search.cpan.org/perldoc?MooseX::Getopt][MooseX::Getopt]] is a
Role that add a =new_with_options= to your object. We create a basic
Object :
#+BEGIN_SRC perl
package OurShinyObject;
use Moose;
with qw/MooseX::Getopt/;
has 'config' => (isa => 'Str', is => 'ro', required => 1);
has 'context' => (
isa => 'HashRef',
is => 'rw',
lazy => 1,
traits => ['NoGetopt'],
default => sub { LoadFile shift->config }
);
...
#+END_SRC
create a script to call this object
#+BEGIN_SRC perl
#!/usr/bin/perl -w
use strict;
use OurShinyObject;
my $obj = OurShinyObject->new_from_options();
#+END_SRC
#+BEGIN_SRC sh
% script.pl --config file.yml
#+END_SRC
The role will set our attribute *context* using the value from the
argument set on the command line.
The =traits => ['NoGetopt']= indicate that this attributes will be not
be read from the command line. An alternate way to do this is to prefix
the attributes with **\_**.
** conclusion (?)
When you write a script, even if you're sure you will never need to have
more than one argument, or that you never will have to update the code,
/please/ consider to use of *Getopt::Long* instead of a =shift @ARGV=,
because we all know that you will at a certain point update this script
and you will more than one argument :).
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