Setting up a job to occur automatically on a regular basis (a cron job) is an immensely useful facility. This is stanard on UNIX-based systems and easy once you know the basics.

Here are a few example crontab entries:
0 2 * * * /home/redcurry/bin/rdf_grabber >& /dev/null
0,5,10,15,20,25,30,35,40,45,50,55 * * * * /usr/local/bin/mrtg /usr/ins/intel/gui/bin/mrtg-cpu.cfg >& /dev/null

Just to translate into English, the first job fires off a script called ‘rdf_grabber’ everynight at 2 am.

The second entry fires off the app ‘mrtg’ using the config file mrtg-cpu.cfg every 5 minutes, 24 hours a day, 7 days a week.

The >& /dev/null bit at the end just takes care of any potential output that might result in case of an error and saves the sysadmin being bombarded by emails.