Log::Log4perl::Config::Watch - Detect file changes
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);
}
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.
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.
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.
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, similarly as with change_detected().
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.
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.
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