NAME

IPC::Cmd::Cached - Run expensive commands and cache their output

SYNOPSIS

    use IPC::Cmd::Cached;

    my $runner = IPC::Cmd::Cached->new();

      # takes a fair mount to run, but result gets cached
    my($success, $error_code, $full_buf, $stdout_buf, $stderr_buf) =
      $runner->run(command => "find /etc -type f -print");

      # Returns the same result much faster, because it's cached
    my($success, $error_code, $full_buf, $stdout_buf, $stderr_buf) =
      $runner->run_cached("find /etc -type f -print");

      # To make sure the cached entries don't expire, run this 
      # twice a day via a cronjob:
    $runner->run_all();

DESCRIPTION

IPC::Cmd::Cached uses IPC::Cmd to run arbitrary shell commands, but caches their results and finds them later.

It uses a Cache::FileCache object to store the output of commands it has successfully executed persistently on disk. Results are store under a key equal to the command line given to run the commands.

If a command's output doesn't change much over time and cached results are acceptable, IPC::Cmd::Cached saves time by reusing canned results instead of recalculating the same results over and over again.

IPC::Cmd::Cached works like the Memoize module, but instead of caching the output of functions, it caches the output of external scripts.

CAVEATS

A command's results are cached based on its full command line. This might not be desirable if the same command produces varying output over time:

    $ eg/run-cached date
    Mon Dec 17 00:01:00 PST 2007
    $ eg/run-cached -c date
    Mon Dec 17 00:01:00 PST 2007

Advanced use cases

The constructor accepts arguments to change the runner's internal behavior:

cache

By default, this is set to a Cache::FileCache object in the default namespace with 24 hours of expiration time:

    my $runner = IPC::Cmd::Cached->new( 
      cache => Cache::FileCache->new({
        auto_purge_on_get  => 1,
        default_expires_in => 24*3600,
        namespace          => "IPC-Cmd-Cached",
      }),
    );

If you need different characteristics, define your own cache object and hand it over to new as shown above. Take a look at the Cache::Cache documentation for details.

EXAMPLES

The distribution comes with two utility scripts, run-cached and run-cached-all.

run-cached runs a command specified on its command line. With the -c option, it will fetch the cached entry instead.

run-cached-all runs all scripts in the cache to refresh their content.

Check the documentation that comes with these scripts for more details.

LEGALESE

Copyright 2007 by Mike Schilli, all rights reserved. This program is free software, you can redistribute it and/or modify it under the same terms as Perl itself.

AUTHOR

2007, Mike Schilli <cpan@perlmeister.com>