Config::Watch(3) User Contributed Perl Documentation Config::Watch(3)
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
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!\n";
}
sleep(1);
}
The parameters "check_interval" and "signal" limit the number of
physical file system checks, similarily 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.
perl v5.30.0 2017-02-21 Config::Watch(3)
log-log4perl 1.490.0 - Generated Mon Jul 20 13:07:20 CDT 2020