Mischief With Cron

So today I learned about Cron. Cron is a way to schedule tasks to be completed automatically in Unix like operating systems. By editing one file you can schedule tasks to be completed by a specific user on a minute - weekly basis. I wanted to bug my sister so I added the following lines to /etc/crontab (Click for more)

#You need beep for this to work. It is in most distributions Repos
#Ignore the tildes (~) they are there for formatting reasons
*/10 * * * * root eject /dev/cdrom/
*/11 * * * * root mount /dev/cdrom/
*/3 * * * * root beep

# ^~~~~~~^~~~~^~~~~~~~^
# |~~~~~~|~~~~|~~~~~~~|------ Destination
# |~~~~~~|~~~~|-------------- Command
# |~~~~~~|------------------- User
# |------------------------------- Time

This means that every 10 minutes her cdrom tray pops out automatically, Every 11 minutes it pops back in automatically and every 3 minutes the internal speaker will beep.

The time syntax can be found in this chart
# ~+---------------- minute (0 - 59)
# ~|~+------------- hour (0 - 23)
# ~|~|~+---------- day of month (1 - 31)
# ~|~|~|~+------- month (1 - 12)
# ~|~|~|~|~+---- day of week (0 - 6) (Sunday=0 or 7)
# ~|~|~|~|~|
# ~*~*~*~*~* command to be executed

*/10 = every number thats divisible in time (days, hours weeks, etc)
* = every (minute, hour, day)
15 = (15th minute, 15th day, 15th hour, ect)

I annoyed her for a good hour before she figured out that I did something to her computer and that it wasn't just a bunch of glitches :D
Have fun playing around with cron. It is a very versatile and easy to use tool!

-Germ