in reply to Cron Question

As other responses have indicatated cron may not be the best solution but you want to use it here is how you could do it...

Schedule it to start at some time say 1:30pm with a cron entry like the following: 

13 30 * * * /path/to/myscript.pl

[download]

Have the program print the pid (available in perl as the var $$) to a file like /tmp/myscript.pid and add a second line to cron like: 

15 30 * * * kill `cat /tmp/myscript.pid`

[download]
To kill the app 2 hour later at 3:30pm. Of course you could make the kill fancier if you didn't want an error if the script had finished running...

In case you were not aware you edit cron with the command crontab -e. See man crontab for more details.

-monkfish (The Fishy Monk)

Replies are listed 'Best First'.
Re (tilly) 2: Cron Question
by tilly (Archbishop) on Nov 08, 2001 at 05:41 UTC
    An important administration sanity tip.

    You don't want to edit crons with crontab -e. If someone messes up your cron, you really, really, really need to be able to fix it.

    Instead do: 

    crontab cron.ctl

    [download]
    where cron.ctl is a file you have in a revision control system. Make all edits through editing cron.ctl then reloading the cron.
[reply]
[d/l]
      I've found that a daily snapshot of current crontabs (in /var/spool/cron/$USER on my linux machine) works fine. Either an automatic cvs check in, or just a tar.gz of modified crontabs. I don't necessarily need an archive of each minor edit made to a crontab during the day, but rolling it back to "the way it worked yesterday" is oft requested.

      Behind the scenes, crontab -e really just automates these two steps: 

      vi $DefaultCrontabFile;       # use your $EDITOR to edit default file
crontab $DefaultCrontabFile;  # install said file

      [download]

      -Blake

[reply]
[d/l]
        I prefer using CVS. If it is already set up, it is no extra work to do things that way, and for that you get the visibility of a change-log, plus automated emails of changes. Using backup policies may work, but you have to remember more about your system configuration and lose visibility for essentially no savings in effort.

        Then again I have to work with crontabs which multiple developers have edit privileges on. When you see something in there that doesn't belong, it is very nice to be able to say, "Who did that?" and get an answer.

        Plus we already use CVS for our source-code. And working from system backups is a pain. With CVS any developer has that visibility in the same way they track anything else, without having to ask anyone for assistance. Without it all recoveries have to go to the sysadmin with the first question being, "Where do we keep the backups?" And then once you know where you keep the backups, "Where does this version of Unix keep its crontabs?" My sysadmin has more important things to do than babysit me through what should be a minor "oops". Rolling back something in a crontab may be a common need, but it needn't be a common request.

        An incidental benefit for some people is that using revision control makes it easy to have multiple machines have the same crontab.

        And finally, revision control is more convenient. For instance I am in the process of modifying some logic about what happens where in the nightly processes we run. It is very convenient that I can edit the crontab file as I am also editing the code for the processes that will run, and then check the associated changes into production together. If I had to make my source-code changes and then remember everything to change in production, then I would be more likely to make mistakes as I take things into production.

        So while keeping backups is sufficient for a personal machine, given the choice I strongly prefer to use revision control. (And I would walk before working on a code-base without any kind of revision control in a shared environment. Revision control isn't very hard to set up, and I don't consider it optional. One vote to the first person who can figure out what famous project I would criticize on this issue...)

[reply]

In Section Seekers of Perl Wisdom