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Getopt::Long.pm - Perl

Over the course of the next few pages, I will introduce you to one of the more interesting modules in the Perl pantheon, the Getopt::Long.pm module. This module provides a simple API to parse options passed to your Perl scripts at the command line and convert them into Perl scalars or arrays.

TABLE OF CONTENTS:
  1. Processing Command Line Options with PERL
  2. The POSIX Standard
  3. Down To Work
  4. GetOptions() Function
  5. Half-Life
  6. Getopt::Long.pm
  7. Opting In
  8. Negative Reinforcement
  9. Hashing It Up
By: icarus, (c) Melonfire
Rating: starstarstarstarstar / 58
March 31, 2004

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It is interesting to note that the equality symbol (=) sign between the option name and the data type specifier tells Getopt::Long.pm that an option value *must* be provided for the option. Look what happens if, for example, you specify the "--age" option without a corresponding integer value:

$ ./script.pl --age
Option age requires an argument

In order to make an option value optional (try saying that fast!), use a colon (:) instead of an equality symbol (=), as below:


#!/usr/bin/perl
 
# import module
use Getopt::Long;
 
# read options
$result = GetOptions ("age:i" => $age);  
      

# print value
print "Input age is $age years";

Here, in the absence of a value for the option, Getopt::Long.pm will automatically assign 0 (for integer values) or an empty string (for string values) to the corresponding option variable. Take a look at the output of the script above to verify this:

$ ./script.pl --age
Input age is 0 years



 
 
>>> More Perl Programming Articles          >>> More By icarus, (c) Melonfire
 

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