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MAN page from RedHat EL 8 perl-Log-Log4perl-1.50-1.el8.noarch.rpm

Config::Watch

Section: User Contributed Perl Documentation (3)
Updated: 2020-07-22
Index 

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 checksif "check_interval" hasn't elapsed.
*
perform a physical test on the specified file if the numberof seconds specified in "check_interval" have elapsed since the last physical check. If the file's modificationdate 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 performinga significant performance penalty because file system operations are being performed (however, you pay the price of not knowing aboutfile 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 amountof time compared to the executing computer's clock, it'll justwork fine.

To disable the resource-saving delay feature, just set "check_interval" to 0 and "change_detected()" will run a physical file test onevery call.

If you already have the current time available, you can pass iton to "change_detected()" as an optional parameter, like in

    change_detected($time)

which then won't trigger a call to "time()", but use the valueprovided. 

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 hasbeen 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 <cpanAATTgoess.org>.

This library is free software; you can redistribute it and/or modifyit 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-develAATTlists.sourceforge.net

Authors (please contact them via the list above, not directly):Mike Schilli <m@perlmeister.com>,Kevin Goess <cpanAATTgoess.org>

Contributors (in alphabetical order):Ateeq Altaf, Cory Bennett, Jens Berthold, Jeremy Bopp, HuttonDavidson, Chris R. Donnelly, Matisse Enzer, Hugh Esco, AnthonyFoiani, James FitzGibbon, Carl Franks, Dennis Gregorovic, AndyGrundman, 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.


 

Index

NAME
SYNOPSIS
DESCRIPTION
SIGNAL MODE
TRIGGER CHECKS
DETECT MOVED FILES
LICENSE
AUTHOR

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