Schedule::Cron
==============
This module provides a simple but complete cron like scheduler. I.e
this modules can be used for periodically executing Perl subroutines.
The dates and parameters for the subroutines to be called are
specified with a format known as crontab entry (see manpage crontab(5)
or documentation of Schedule::Cron).
The philosophy behind Schedule::Cron is to call subroutines
periodically from within one single Perl program instead of letting
cron trigger several (possibly different) Perl scripts. Everything
under one roof. Furthermore Schedule::Cron provides mechanism to
create crontab entries dynamically, which isn't that easy with cron.
Schedule::Cron knows about all extensions (well, at least all
extensions I'm aware of, i.e those of the so called "Vixie" cron) for
crontab entries like ranges including 'steps', specification of month
and days of the week by name or coexistence of lists and ranges in the
same field. And even a bit more (like lists and ranges with symbolic
names).
This module is rather effective concerning system load. It calculates
the execution dates in advance and will sleep until those dates are
reached (and wont wake up every minute to check for execution like
cron). However, it relies on the accuracy of your sleep() system
call.
EXAMPLES
--------
* Minimalistic:
use Schedule::Cron;
my $dispatcher = sub { print "Time to start...\n"};
my $cron = new Schedule::Cron($dispatcher);
$cron->add_entry("0 7 * * *");
$cron->run; # Runs forever...
* A bit more complex:
use Schedule::Cron;
my $cron = new Schedule::Cron( sub { print "@_","\n" },
file => "check_links.sched",
eval => 1);
sub check_links {
my $args = shift;
print "URL: ",$args->{url},"\n";
print "Depth: ",$args->{depth},"\n";
}
$cron->add_entry("0-40/5,55 3,22 * Jan-Nov Fri",
{ sub => \&check_links,
args => [ { url => "
http://www.consol.de",
depth => 2 } ],
eval => 0 });
# ... add more ....
$cron->run(detach=>1,pid_file=>"/var/run/checker.pid");
# ... continue ...
* simple cron replacement (for a single crontab file):
use Schedule::Cron;
my $cron = new Schedule::Cron(sub { system(shift) },
file => "/var/spool/crontab.perl");
$cron->run();
PREREQUISITES
-------------
In order to install and use this package you will need Perl version
5.005 or better. Furthermore you need the module Time::ParseDate
(contained in the Time-modules-xx.xxxxx) available on CPAN.
You need a fork()-aware Perl for dispatching the cron jobs. (Honestly,
I don't yet know, whether the Win32 Port provides this system call. I
dare that this is the case). This might change in the future.
OS-DEPENDENCIES
---------------
Schedule::Cron was tested on a Redhat Linux-Box, but it should work on
any UNIX Box (still to be tested). In depends on some UNIX system
calls for starting jobs and detaching itself to the background:
* It uses fork() for starting jobs
* For detaching it uses either setsid (POSIX) or the ioctl call
TIOCNOTTY
So at the moment, it probably won't run on any 'foreign' ports like
the Win32- or MacOs-Port.
These restrictions might be relaxed in the future.
INSTALLATION
------------
As usual:
perl Makefile.PL
make
make test
make install
See the documentation for Schedule::Cron for a detailed description
and further usage examples.
REPORTING BUGS
--------------
This module is still in alpha stage, so I expect probably some bugs
showing up. I.e. the calculation of the next execution time of a
specific crontab entry might fail in some obscure circumstances
(though I did what I could to test it thoroughly).
If you meet a bug (say hello to it ;-), please report it to
[email protected] with a subject like "Schedule::Cron Bug-Report". In
addition of a problem description, please add a short description of
you OS, your Perl version and the version of Time::ParseDate you are
using. If some of the provided tests fail, include the output of 'make
test TEST_VERBOSE=1' as well.
If you suspect, that the date calculation of the next execution time
is buggy, please use the following interactive command to generate a
bug report.
perl -MSchedule::Cron -e 'bug Schedule::Cron'
You will be asked for a reference time (default: the current time), a
crontab date pattern (with five columns) and the expected next
execution date (relative to the reference time). The dates can be
specified in a format understood by 'parsedate' from Time::ParseDate
(like 'now + 5 days'). Please include the output of this command.
CREDITS
-------
Many thanks to
Peter Vary
Bray Jones
David Parker
Philippe Verdret
Lars Holowko
for submitting bug reports and patches.
COPYRIGHT
---------
Copyright 1999,2000 Roland Huss.
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
Enjoy it...
...roland
[email protected]
