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page-watcher 1.0.0 (Default branch)
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Config::Watch(3pm) User Contributed Perl Documentation Config::Watch(3pm) 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! "; } 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 o return a false value immediately without doing physical file checks if "check_interval" hasn't elapsed. o 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! "; } sleep(1); } The parameters "check_interval" and "signal" limit the number of physical file system checks, simililarily as with "change_detected()". COPYRIGHT AND LICENSE
Copyright 2002-2009 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. perl v5.10.1 2010-07-21 Config::Watch(3pm)
