Config::Watch(3) User Contributed Perl Documentation Config::Watch(3)NAMELog::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, 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 v5.14.1 2011-05-02 Config::Watch(3)
