On Sunday, I spent a good half-hour with Google learning how to launch a GUI application in Ubuntu using cron. I wanted to write a brief post here explaining the process so as to help another weary Googler more quickly on their way.
My situation is this: I use a nifty little flashcard-like study program called Mnemosyne. I use it to study foreign languages and for school. Ideally I should run it daily — but I often forget, which slows my learning. So I decided to create a cron job which would run the program every day at 7 AM.
Using the normal crontab syntax I made this entry:
0 7 * * * mnemosyne
This, I thought, would run mnemosyne once a day at 7 AM. Unfortunately I was wrong. After much searching around I found the solution on the Ubuntu forums (always a great resource). My problem was that because cron doesn’t run in the X session (The program that controls all GUIs in Linux), when you try to run a GUI program, cron doesn’t know where to start it. To tell cron where to start the GUI, I changed my crontab entry as follows:
0 7 * * * export DISPLAY=:0 && /usr/bin/mnemosyne
And finally success!
The post on the Ubuntu Forums I found explains all this and more and gives a number of examples.
Also, for those wanting a more general tutorial on crontab syntax, see the crontab article on wikipedia.
Posted May 02, 2007
Kyle Mathews lives and works in San Francisco building useful things. You should follow him on Twitter