File::Modified(3pm)					User Contributed Perl Documentation				       File::Modified(3pm)

NAME

       File::Modified - checks intelligently if files have changed

SYNOPSIS

	 use strict;
	 use File::Modified;

	 my $d = File::Modified->new(files=>['Import.cfg','Export.cfg']);

	 while(1) {
	   my (@changes) = $d->changed;

	   if (@changes) {
	     print "$_ was changed
" for @changes;
	     $d->update();
	   };
	   sleep 60;
	 };

       Second example - a script that knows when any of its modules have changed :

	 use File::Modified;
	 my $files = File::Modified->new(files=>[values %INC, $0]);

	 # We want to restart when any module was changed
	 exec $0, @ARGV if $files->changed();

DESCRIPTION

       The Modified module is intended as a simple method for programs to detect whether configuration files (or modules they rely on) have
       changed. There are currently two methods of change detection implemented, "mtime" and "MD5".  The "MD5" method will fall back to use time-
       stamps if the "Digest::MD5" module cannot be loaded.

       There is another module, File::Signature, which has many similar features, so if this module doesn't do what you need, maybe File::Signa-
       ture does. There also is quite some overlap between the two modules, code wise.

       new %ARGS
	   Creates a new instance. The %ARGS hash has two possible keys, "Method", which denotes the method used for checking as default, and
	   "Files", which takes an array reference to the filenames to watch.

       add filename, method
	   Adds a new file to watch. "method" is the method (or rather, the subclass of "File::Modified::Signature") to use to determine whether a
	   file has changed or not. The result is either the "File::Modified::Signature" subclass or undef if an error occurred.

       addfile LIST
	   Adds a list of files to watch. The method used for watching is the default method as set in the constructor. The result is a list of
	   "File::Modified::Signature" subclasses.

       update
	   Updates all signatures to the current state. All pending changes are discarded.

       changed
	   Returns a list of the filenames whose files did change since the construction or the last call to "update" (whichever last occurred).

       Signatures

       The module also creates a new namespace "File::Signature", which sometime will evolve into its own module in its own file. A file signature
       is most likely of little interest to you; the only time you might want to access the signature directly is to store the signature in a file
       for persistence and easy comparision whether an index database is current with the actual data.

       The interface is settled, there are two methods, "as_scalar" and "from_scalar", that you use to freeze and thaw the signatures. The imple-
       mentation of these methods is very frugal, there are no provisions made against filenames that contain weird characters like "
" or "|"
       (the pipe bar), both will be likely to mess up your one-line-per-file database. An interesting method could be to URL-encode all filenames,
       but I will visit this topic in the next release. Also, complex (that is, non-scalar) signatures are handled rather ungraceful at the
       moment.

       Currently, I'm planning to use Text::Quote as a quoting mechanism to protect against multiline filenames.

       Adding new methods for signatures

       Adding a new signature method is as simple as creating a new subclass of "File::Signature". See "File::Signature::Checksum" for a simple
       example. There is one point of laziness in the implementation of "File::Signature", the "check" method can only compare strings instead of
       arbitrary structures (yes, there ARE things that are easier in Python than in Perl). "File::Signature::Digest" is a wrapper for Gisle Aas'
       Digest module and allows you to use any module below the "Digest" namespace as a signature, for example "File::Signature::MD5" and
       "File::Signature::SHA1".

       TODO

       * Make the simple persistence solution for the signatures better using Text::Quote.

       * Allow complex structures for the signatures.

       * Document "File::Modified::Signature" or put it down into another namespace.

       * Extract the "File::Modified::Signature" subclasses out into their own file.

       * Create an easy option to watch a whole directory tree.

       EXPORT

       None by default.

       COPYRIGHT AND LICENSE

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

       Copyright (C) 2002 Max Maischein

AUTHOR

       Max Maischein, <corion@cpan.org>

       Please contact me if you find bugs or otherwise improve the module. More tests are also very welcome !

SEE ALSO

       perl,Digest::MD5,Digest, File::Signature.

perl v5.8.8							    2008-03-21						       File::Modified(3pm)