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Perl 5 version 12.4 documentation
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config_data - Query or change configuration of Perl modules


  1. # Get config/feature values
  2. config_data --module Foo::Bar --feature bazzable
  3. config_data --module Foo::Bar --config magic_number
  4. # Set config/feature values
  5. config_data --module Foo::Bar --set_feature bazzable=1
  6. config_data --module Foo::Bar --set_config magic_number=42
  7. # Print a usage message
  8. config_data --help


The config_data tool provides a command-line interface to the configuration of Perl modules. By "configuration", we mean something akin to "user preferences" or "local settings". This is a formalization and abstraction of the systems that people like Andreas Koenig (CPAN::Config ), Jon Swartz (HTML::Mason::Config ), Andy Wardley (Template::Config ), and Larry Wall (perl's own have developed independently.

The configuration system emplyed here was developed in the context of Module::Build . Under this system, configuration information for a module Foo , for example, is stored in a module called Foo::ConfigData ) (I would have called it Foo::Config , but that was taken by all those other systems mentioned in the previous paragraph...). These ...::ConfigData modules contain the configuration data, as well as publically accessible methods for querying and setting (yes, actually re-writing) the configuration data. The config_data script (whose docs you are currently reading) is merely a front-end for those methods. If you wish, you may create alternate front-ends.

The two types of data that may be stored are called config values and feature values. A config value may be any perl scalar, including references to complex data structures. It must, however, be serializable using Data::Dumper . A feature is a boolean (1 or 0) value.


This script functions as a basic getter/setter wrapper around the configuration of a single module. On the command line, specify which module's configuration you're interested in, and pass options to get or set config or feature values. The following options are supported:

  • module

    Specifies the name of the module to configure (required).

  • feature

    When passed the name of a feature , shows its value. The value will be 1 if the feature is enabled, 0 if the feature is not enabled, or empty if the feature is unknown. When no feature name is supplied, the names and values of all known features will be shown.

  • config

    When passed the name of a config entry, shows its value. The value will be displayed using Data::Dumper (or similar) as perl code. When no config name is supplied, the names and values of all known config entries will be shown.

  • set_feature

    Sets the given feature to the given boolean value. Specify the value as either 1 or 0.

  • set_config

    Sets the given config entry to the given value.

  • eval

    If the --eval option is used, the values in set_config will be evaluated as perl code before being stored. This allows moderately complicated data structures to be stored. For really complicated structures, you probably shouldn't use this command-line interface, just use the Perl API instead.

  • help

    Prints a help message, including a few examples, and exits.


Ken Williams,


Copyright (c) 1999, Ken Williams. All rights reserved.

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


Module::Build(3), perl(1).