User Crontab + Python + Random wallpapers = Not working?

Question

I have a python script that correctly sets the desktop wallpaper via gconf to a random picture in a given folder.

I then have the following entry in my crontab

* * * * * python /home/bolster/bin/change-background.py

And syslog correctly reports execution

Apr 26 14:11:01 bolster-desktop CRON[9751]: (bolster) CMD (python /home/bolster/bin/change-background.py)
Apr 26 14:12:01 bolster-desktop CRON[9836]: (bolster) CMD (python /home/bolster/bin/change-background.py)
Apr 26 14:13:01 bolster-desktop CRON[9860]: (bolster) CMD (python /home/bolster/bin/change-background.py)
Apr 26 14:14:01 bolster-desktop CRON[9905]: (bolster) CMD (python /home/bolster/bin/change-background.py)
Apr 26 14:15:01 bolster-desktop CRON[9948]: (bolster) CMD (python /home/bolster/bin/change-background.py)
Apr 26 14:16:01 bolster-desktop CRON[9983]: (bolster) CMD (python /home/bolster/bin/change-background.py)

But no desktopy changey, Any ideas?

Answer 1

Your script depends on the DISPLAY environment variable, which is set when you execute the script from the shell in an X session, but unset when the script is run from cron.