File::Modified(3pm)

1File::Modified(3)     User Contributed Perl Documentation    File::Modified(3)
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NAME

6       File::Modified - checks intelligently if files have changed
7

SYNOPSIS

9         use strict;
10         use File::Modified;
11
12         my $d = File::Modified->new(files=>['Import.cfg','Export.cfg']);
13
14         while (1) {
15           my (@changes) = $d->changed;
16
17           if (@changes) {
18             print "$_ was changed\n" for @changes;
19             $d->update();
20           };
21           sleep 60;
22         };
23
24       Second example - a script that knows when any of its modules have
25       changed :
26
27         use File::Modified;
28         my $files = File::Modified->new(files=>[values %INC, $0]);
29
30         # We want to restart when any module was changed
31         exec $0, @ARGV if $files->changed();
32

DESCRIPTION

34       The Modified module is intended as a simple method for programs to
35       detect whether configuration files (or modules they rely on) have
36       changed. There are currently two methods of change detection
37       implemented, "mtime" and "MD5".  The "MD5" method will fall back to use
38       timestamps if the "Digest::MD5" module cannot be loaded.
39
40       There is another module, File::Signature, which has many similar
41       features, so if this module doesn't do what you need, maybe
42       File::Signature does. There also is quite some overlap between the two
43       modules, code wise.
44
45       new %ARGS
46           Creates a new instance. The %ARGS hash has two possible keys,
47           "Method", which denotes the method used for checking as default,
48           and "Files", which takes an array reference to the filenames to
49           watch.
50
51       add filename, method
52           Adds a new file to watch. "method" is the method (or rather, the
53           subclass of "File::Modified::Signature") to use to determine
54           whether a file has changed or not. The result is either the
55           "File::Modified::Signature" subclass or undef if an error occurred.
56
57       addfile LIST
58           Adds a list of files to watch. The method used for watching is the
59           default method as set in the constructor. The result is a list of
60           "File::Modified::Signature" subclasses.
61
62       update
63           Updates all signatures to the current state. All pending changes
64           are discarded.
65
66       changed
67           Returns a list of the filenames whose files did change since the
68           construction or the last call to "update" (whichever last
69           occurred).
70
71   Signatures
72       The module also creates a new namespace "File::Signature", which
73       sometime will evolve into its own module in its own file. A file
74       signature is most likely of little interest to you; the only time you
75       might want to access the signature directly is to store the signature
76       in a file for persistence and easy comparision whether an index
77       database is current with the actual data.
78
79       The interface is settled, there are two methods, "as_scalar" and
80       "from_scalar", that you use to freeze and thaw the signatures. The
81       implementation of these methods is very frugal, there are no provisions
82       made against filenames that contain weird characters like "\n" or "|"
83       (the pipe bar), both will be likely to mess up your one-line-per-file
84       database. An interesting method could be to URL-encode all filenames,
85       but I will visit this topic in the next release. Also, complex (that
86       is, non-scalar) signatures are handled rather ungraceful at the moment.
87
88       Currently, I'm planning to use Text::Quote as a quoting mechanism to
89       protect against multiline filenames.
90
91   Adding new methods for signatures
92       Adding a new signature method is as simple as creating a new subclass
93       of "File::Signature". See "File::Signature::Checksum" for a simple
94       example. There is one point of laziness in the implementation of
95       "File::Signature", the "check" method can only compare strings instead
96       of arbitrary structures (yes, there ARE things that are easier in
97       Python than in Perl). "File::Signature::Digest" is a wrapper for Gisle
98       Aas' Digest module and allows you to use any module below the "Digest"
99       namespace as a signature, for example "File::Signature::MD5" and
100       "File::Signature::SHA1".
101
102   TODO
103       * Make the simple persistence solution for the signatures better using
104       Text::Quote.
105
106       * Allow complex structures for the signatures.
107
108       * Document "File::Modified::Signature" or put it down into another
109       namespace.
110
111       * Extract the "File::Modified::Signature" subclasses out into their own
112       file.
113
114       * Create an easy option to watch a whole directory tree.
115
116   EXPORT
117       None by default.
118
119   COPYRIGHT AND LICENSE
120       This library is free software; you can redistribute it and/or modify it
121       under the same terms as Perl itself.
122
123       Copyright (C) 2002 Max Maischein
124

AUTHOR

126       Max Maischein, <corion@cpan.org>
127
128       Please contact me if you find bugs or otherwise improve the module.
129       More tests are also very welcome !
130

NAME

SYNOPSIS

DESCRIPTION

AUTHOR

SEE ALSO