Run cron job only if it isn't already running

Question

I\'m trying to set up a cron job as a sort of watchdog for a daemon that I\'ve created. If the daemon errors out and fails, I want the cron job to periodically restart it...

Answer 1

It's suprising that no one mentioned about run-one. I've solved my problem with this.

 apt-get install run-one

then add run-one before your crontab script

*/20 * * * * * run-one python /script/to/run/awesome.py

Check out this askubuntu SE answer. You can find link to a detailed information there as well.