cron functionality mimic in perl scripting

coolfire has asked for the wisdom of the Perl Monks concerning the following question:

Hey Monks, I'm a moderate skilled perl person trying to mimic the 'cron' functionality of *nix systems without using any modules. What I'm doing is fork a child and running an infinite loop:

my $interval = 300;
my $cpid = fork();
my $upto = localtime() + $interval;
while (1) {
  if ($upto == localtime()) {
    $upto = localtime() + $interval;
    system("/home/rambo/perl-assignments/send_test_mail.pl");
  }
  sleep 1;
}
[download]

My question is how can I do this if I have three or more jobs which runs at different intervals? Can it be possible to put above in a sub and do a foreach of different intervals/scripts to be executed? I'm thinking of a timer kind of thing which forks(parallel forks if more), execs respective script and kills child after.

Comment on cron functionality mimic in perl scripting Download Code

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Re: cron functionality mimic in perl scripting by Corion (Patriarch) on Sep 20, 2011 at 11:46 UTC
Have a look at how Schedule::Cron does it, and then program the same thing yourself. Or, you could just use Schedule::Cron. See Yes, even you can use CPAN and local::lib.	[reply]
Re: cron functionality mimic in perl scripting by moritz (Cardinal) on Sep 20, 2011 at 11:46 UTC
You can fork once for each interval, and then in each child run the sleep + system loop. Or you could use some system that has timers built in, I guess most of the event loops (POE, AnyEvent etc.) have such a facility. Or use Schedule::Cron. Perl 6 - second systems done right	[reply]
Re: cron functionality mimic in perl scripting by jwkrahn (Abbot) on Sep 20, 2011 at 12:34 UTC
`if ($upto == localtime()) { $upto = localtime() + $interval;` [download] localtime returns a string in scalar context and you can't properly do arithmetic operations on a string. `$ perl -le'print scalar localtime' Tue Sep 20 05:32:46 2011` [download] Perhaps you meant to use time instead?	[reply] [d/l] [select]
Re: cron functionality mimic in perl scripting by jethro (Monsignor) on Sep 20, 2011 at 12:01 UTC
I suspect that cron just has a ordered list of times the different jobs have to be started and checks every second if the first entries in the list have to be started. It is a bit inefficient to have a process hanging around for every single job in the queue	[reply]
Re: cron functionality mimic in perl scripting by zentara (Cardinal) on Sep 20, 2011 at 15:47 UTC
My question is how can I do this if I have three or more jobs which runs at different intervals? You would be better off using an event-loop system, many to choose from, and setup timers. I'm not really a human, but I play one on earth. Old Perl Programmer Haiku ................... flash japh	[reply]