CPAN::AutoINC - Download and install CPAN modules upon first use

perl -MCPAN::AutoINC <script>

When CPAN::AutoINC is loaded, it will add itself to @INC and catch any requests for missing resources. If a Perl module is requested CPAN will be queried and, assuming that the module exists on CPAN, CPAN::Shell will be invoked to install it. Execution of the script continues after the requisite module has been installed.

CPAN::AutoINC is a slightly useful tool designed to streamline the process of installing all of the modules required by a script. By loading the CPAN::AutoINC module (usually via a "-MCPAN::AutoINC" command-line option), the user is registering a handler that will catch any attempt to use a module that does not exist on the local machine. In this case, the CPAN::Shell module will be invoked to search for the specified module and, if found, an attempt will be made to install the module. If successful, the module will be loaded and execution will continue as normal.

For example:

perl -MCPAN::AutoINC -MLingua::Num2Word=cardinal -le 'print cardinal("en", 42)'

...will download and install Lingua::Num2Word and Lingua::EN::Num2Word.

perl -MCPAN::AutoINC -MLingua::Num2Word=cardinal -le 'print cardinal("de", 42)'

...will then download and install Lingua::DE::Num2Word (German).

perl -MCPAN::AutoINC -MLingua::Num2Word=cardinal -le 'print cardinal("es", 42)'

...will then download and install Lingua::ES::Numeros (Spanish).

• The "CPAN" module must be properly configured to run for the user whom you plan to be when you execute your scripts. By default CPAN tends to install into a system path (e.g., /usr/lib/perl), so you would need to run your scripts as root for this to work transparently. However, you can also configure CPAN for other users by installing a ~/.cpan/CPAN/MyConfig.pm file. In particular, you may want to override makepl_arg to add a "PREFIX=~/.cpan/install" setting.
• Make sure that the directory where your Perl modules are installed is in your @INC by default, either by adding a -I option to your command line or by seting your $PERL5LIB environmental variable. This is most likely only necessary if you are not running your scripts as root.
• If the entire directory structure does not exist the first time you use CPAN::AutoINC, you may need to run your script twice. For example, if your PREFIX is set to "~/.cpan/install" and your PERL5LIB is set to "~/.cpan/install/perl5:~/.cpan/install/perl5/site_perl", ~/.cpan/install/perl5/site_perl/5.8.0 and ~/.cpan/install/perl5/site_perl/5.8.0/i686-linux will not be added to your @INC unless they existed before your module was installed. In this case loading of the installed module would fail and you would need to re-run your script.
• You may wish to configure CPAN to always follow dependencies. This can be done by setting your 'prerequisites_policy' option to 'follow'. However, this doesn't guarantee that all module installations will go smoothly without human intervention; some installation or test procedures explicitly prompt the user.
• It seems that the CPAN module itself uses Log::Agent somehow, so you will likely see this installed as the first module.

The description for the Acme::RemoteINC CPAN module ("Slowest Possible Module Loading") prompted me to write this module. The only thing slower than loading precompiled modules via FTP is loading module source code from FTP and compiling it. Except maybe carrier pigeons.

As you can see from the CAVEATS section, there is a fair amount of set-up work required and it will not work for all modules. This makes it relatively useless, especially in a production environment. But it's a cool hack, and could potentially be useful under very limited circumstances.

Don Schwarz, <don@schwarz.name>

Copyright 2004 by Don Schwarz

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