NAME

       Log::Log4perl::Config::Watch - Detect file changes

SYNOPSIS

           use Log::Log4perl::Config::Watch;

           my $watcher = Log::Log4perl::Config::Watch->new(
                                 file            => "/data/my.conf",
                                 check_interval  => 30,
                         );

           while(1) {
               if($watcher->change_detected()) {
                   print "Change detected!\n";
               }
               sleep(1);
           }

DESCRIPTION

       This module helps detecting changes in files. Although it comes with the "Log::Log4perl"
       distribution, it can be used independently.

       The constructor defines the file to be watched and the check interval in seconds.
       Subsequent calls to "change_detected()" will

       •   return a false value immediately without doing physical file checks if
           "check_interval" hasn't elapsed.

       •   perform a physical test on the specified file if the number of seconds specified in
           "check_interval" have elapsed since the last physical check. If the file's
           modification date has changed since the last physical check, it will return a true
           value, otherwise a false value is returned.

       Bottom line: "check_interval" allows you to call the function "change_detected()" as often
       as you like, without paying the performing a significant performance penalty because file
       system operations are being performed (however, you pay the price of not knowing about
       file changes until "check_interval" seconds have elapsed).

       The module clearly distinguishes system time from file system time.  If your (e.g. NFS
       mounted) file system is off by a constant amount of time compared to the executing
       computer's clock, it'll just work fine.

       To disable the resource-saving delay feature, just set "check_interval" to 0 and
       "change_detected()" will run a physical file test on every call.

       If you already have the current time available, you can pass it on to "change_detected()"
       as an optional parameter, like in

           change_detected($time)

       which then won't trigger a call to "time()", but use the value provided.

   SIGNAL MODE
       Instead of polling time and file changes, "new()" can be instructed to set up a signal
       handler. If you call the constructor like

           my $watcher = Log::Log4perl::Config::Watch->new(
                                 file    => "/data/my.conf",
                                 signal  => 'HUP'
                         );

       then a signal handler will be installed, setting the object's variable
       "$self->{signal_caught}" to a true value when the signal arrives.  Comes with all the
       problems that signal handlers go along with.

   TRIGGER CHECKS
       To trigger a physical file check on the next call to "change_detected()" regardless if
       "check_interval" has expired or not, call

           $watcher->force_next_check();

       on the watcher object.

   DETECT MOVED FILES
       The watcher can also be used to detect files that have moved. It will not only detect if a
       watched file has disappeared, but also if it has been replaced by a new file in the
       meantime.

           my $watcher = Log::Log4perl::Config::Watch->new(
               file           => "/data/my.conf",
               check_interval => 30,
           );

           while(1) {
               if($watcher->file_has_moved()) {
                   print "File has moved!\n";
               }
               sleep(1);
           }

       The parameters "check_interval" and "signal" limit the number of physical file system
       checks, simililarily as with "change_detected()".

LICENSE

       Copyright 2002-2013 by Mike Schilli <m@perlmeister.com> and Kevin Goess <cpan@goess.org>.

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

AUTHOR

       Please contribute patches to the project on Github:

           http://github.com/mschilli/log4perl

       Send bug reports or requests for enhancements to the authors via our

       MAILING LIST (questions, bug reports, suggestions/patches):
       log4perl-devel@lists.sourceforge.net

       Authors (please contact them via the list above, not directly): Mike Schilli
       <m@perlmeister.com>, Kevin Goess <cpan@goess.org>

       Contributors (in alphabetical order): Ateeq Altaf, Cory Bennett, Jens Berthold, Jeremy
       Bopp, Hutton Davidson, Chris R. Donnelly, Matisse Enzer, Hugh Esco, Anthony Foiani, James
       FitzGibbon, Carl Franks, Dennis Gregorovic, Andy Grundman, Paul Harrington, Alexander
       Hartmaier  David Hull, Robert Jacobson, Jason Kohles, Jeff Macdonald, Markus Peter, Brett
       Rann, Peter Rabbitson, Erik Selberg, Aaron Straup Cope, Lars Thegler, David Viner, Mac
       Yang.