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, 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.