How to submit cron jobs?

Shell Programming and Scripting
1

How can I write a script to submit a perl script as a cron job but only have it execute once?

After it has executed once, I would like it to automatically insert itself again into cron.

I want to avoid the situation where I schedule a cron job to run once a day, but end up with multiple instances of the cron job because it requires more than 24 hours to execute.

Thanks,
Siegfried

2

just have your perl script check to see if it is already running. if so then don't run.

3

How do I check to see if it is still running?

Let is supposed I set a flag in a database and I clear the flag when the perl script exits.

What happens if the perl script access violates and executes before it clears the flag?

Then I will never run thinking I am already running!

Thanks,
Siegfried

4

Install a signal handler that looks for SIGINT, or whatever, and delete the file there. I don't program for a living so I can't give you expert advice there.

5

Put your job in a loop inside a shell script. Trap your error of your perl script in the loop. Put this shell script on cron.