Open and close a program at specific times in cron

brgsousa · 03-10-2009, 09:33 AM

Guys,
How can I schedule cron to open and close a program at specific times?
I just don't know how to schedule it to close automatically.

Regards

crabboy · 03-10-2009, 10:28 AM

The cron job that stops the process will have to search for the process by name and kill it. A better approach may be to have the start script save off the processes PID into a file and the stop process can read the pid (verify the name) and then kill it. Care should be taken killing off the process, some programs are programed to respond to a TERM signal and exit gracefully, others are not.

jlinkels · 03-10-2009, 01:38 PM

More specifically the start-up script:

Code:

#! /bin/bash
/full/path/to/your/program > /dev/null &
echo $! > /var/tmp/myprogrampidfile.pid
exit

and shutdown:

Code:

#! /bin/bash
if [ -f /var/tmp/myprogrampidfile.pid ]
then
   /bin/kill $(cat /var/tmp/myprogrampidfile.pid)
fi

Make sure you redirect the output of your program to something else but stderr or stdout.

Use full paths everywhere.

If you run the cron job with root permissions you can store your pid file in /var/run, which is nicer.

Test the scripts outside cron first.

This is untested code!

jlinkels

brgsousa · 03-11-2009, 08:41 AM

Thanks!
it worked

brgsousa · 03-11-2009, 09:09 AM

I need to start rtorrent from cron. But trying to execute it directly doesn't work, so I'm using screen to execute it, like this:
0 19 * * * /usr/bin/screen -d -m /usr/bin/rtorrent

How can I retain rtorrent PID in this situation?