NAME
   File::CacheDir - Perl module to aid in keeping track and cleaning up
   files, quickly and without a cron $Id: CacheDir.pm,v 1.15 2001/10/16
   17:07:57 earl Exp $

SYNOPSIS
   CacheDir takes up to three parameters and returns a fully qualified
   filename. Cool part is that it quickly and automatically cleans up files
   that are too old.

ARGUMENTS
   The possible named arguments (which can be named or sent in a hash ref,
   see below for an example) are,

   filename - which is what you want the file without the directory to be
   named, like "storebuilder" . time . $$ I would suggest using a script
   specific word (like the name of the cgi), time and $$ (which is the pid
   number) in the filename, just so files are easy to track and the
   filenames are pretty unique default is time . $$

   ttl - how long you want the file to stick around can be given in seconds
   (3600) or like "1 hour" or "1 day" or even "1 week" default is '1 day'

   base_dir - the base directory default is '/tmp/cache_dir'

   content_typed - whether or not you have printed a Content-type header
   default is 0

   set_cookie - whether or not to set a cookie default is 0

   cookie_name - the name of your cookie default is 'cache_dir'

   cookie_path - the path for your cookie default is '/'

   carry_forward - whether or not to move forward the file when time
   periods get crossed for example if your ttl is 3600, and you move from
   the 278711 to the 278712 hour, if carry forward is set, it will refresh
   a cookie (if set_cookie is true) and move the file to the new location
   default is 1

COOOKIES
   Since CacheDir fits in so nicely with cookies, I use a few CGI methods
   to automatically set cookies, retrieve the cookies, and use the cookies
   when applicable. The cookie methods make it near trivial to handle
   session information. Taking the advice of Rob Brown
   <[email protected]>, I use CGI.pm, though it increases load time and
   nearly doubles out of the box memory required.

   The cookie that gets set is the full path of the file with your base_dir
   swapped out. This makes it nice for users to not know full path to your
   files. The filename that gets returned from a cache_dir call, however is
   the full path.

CODE REF OVERRIDES
   Most of the time, the defaults will suffice, but by having code refs in
   your object, you can override most everything CacheDir does. To how the
   code refs are used, I walk through the code with a simple example.

   my $cache_dir = File::CacheDir->new({ base_dir => '/tmp/example', ttl =>
   '2 hours', filename => 'example.' . time . ".$$", });

   An object gets created, with the hash passed getting blessed in.

   my $filename = $cache_dir->cache_dir;

   The ttl gets converted to seconds, here 7200. The

   $ttl_dir = $base_dir . $ttl;

   In our example, $ttl_dir = "/tmp/example/7200";

   $self->{ttl_mkpath} - if the ttl directory does not exist, it gets made
   with this code ref

   Next, the number of ttl units since epoch, here it is something like
   137738. This is

   $self->{int_time} = int(time/$self->{ttl});

   Now, the full directory can be formed

   $self->{full_dir} = $ttl_dir . $self->{int_time};

   If $self->{full_dir} exists, $self->{full_dir} . $self->{filename} gets
   returned. Otherwise, I look through the $ttl_dir, and for each directory
   that is too old (more than two units away) I run

   $self->{cleanup} - just deletes the old directory, but this is where a
   backup could take place, or whatever you like.

   Finally, I

   $self->{sub_mkdir} - makes the new directory, $self->{full_dir}

   and return the $filename

SIMPLE EXAMPLE
     #!/usr/bin/perl -w

     use strict;
     use File::CacheDir qw(cache_dir);

     my $filename = cache_dir({
       base_dir => '/tmp',
       ttl      => '2 hours',
       filename => 'example.' . time . ".$$",
     });

     `touch $filename`;

THANKS
   Thanks to Rob Brown <[email protected]> for discussing general
   concepts, helping me think through things, offering suggestions and
   doing the most recent code review. The idea for carry_forward was pretty
   well all Rob. I didn't see a need, but Rob convinced me of one. Since
   Rob first introduced the idea to me, I have seen CacheDir break three
   different programmers code. With carry_forward, no problems. Finally,
   Rob changed my non-CGI cookie stuff to use CGI thus avoiding many a
   flame war.

   Thanks to Paul T Seamons <[email protected]> for listening to my ideas,
   offerings suggestions, using CacheDir and giving feedback. Using
   File::CacheDir was all Paul's idea. Also, the case of CacheDir and
   cache_dir I owe to Paul. Finally, thanks to Paul for the idea of this
   THANKS section.

   Thanks to Wes Cerny <[email protected]> for using CacheDir, and
   giving feedback. Also, thanks to Wes for a last minute code review. Wes
   had me change the -e check on $self->{carry_forward_filename} to -f,
   based on his experience with CacheDir.

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