| File::Modified - checks intelligently if files have changed |
File::Modified - checks intelligently if files have changed
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\n" 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();
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 timestamps if the Digest::MD5 module
cannot be loaded.
There is another module, the File::Signature manpage, which has many similar features, so if this module doesn't do what you need, maybe File::Signature does. There also is quite some overlap between the two modules, code wise.
%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.
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.
File::Modified::Signature subclasses.
update (whichever last
occurred).
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 implementation of these methods
is very frugal, there are no provisions made against filenames that contain weird
characters like \n 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 the Text::Quote manpage as a quoting mechanism to protect against multiline filenames.
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' the Digest manpage module and allows you to use any module below
the Digest namespace as a signature, for example File::Signature::MD5 and
File::Signature::SHA1.
* Make the simple persistence solution for the signatures better using the Text::Quote manpage.
* 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.
None by default.
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
Max Maischein, <corion@cpan.org>
Please contact me if you find bugs or otherwise improve the module. More tests are also very welcome !
the perl manpage,the Digest::MD5 manpage,the Digest manpage, the File::Signature manpage.
| File::Modified - checks intelligently if files have changed |