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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!\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, similarly as with "change_detected()".
LICENSE
Copyright 2002-2013 by Mike Schilli <m AT perlmeister.com> and Kevin Goess <cpan AT 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 AT lists.net
Authors (please contact them via the list above, not directly): Mike Schilli
<m AT perlmeister.com>, Kevin Goess <cpan AT 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 v5.26.0 2017-08-01 Config::Watch(3pm)
Generated by $Id: phpMan.php,v 4.55 2007/09/05 04:42:51 chedong Exp $ Author: Che Dong
On Apache
Under GNU General Public License
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