On my Ubuntu 10.10 system I have the computer set to sleep after 1 hour of inactivity. I set this with the GUI Gnome Power Manager preference panel.

I want to create a bash script to alter the setting to Never, do some lengthy processing overnight (Blender rendering), then when the processing is done, set the preference back to "sleep after 1 hour of inactivity".

Bash commands gnome-power-manager and gnome-power-preferences offer no settable options, and my searches for an alternative have come up blank.

How can I get this done?

Is your PC going asleep in the middle of the rendering process?

Yes, it is. Aparently inactivity is defined as no mouse and keyboard action, not taking account of CPU activity. That's why I need to change the setting before and after the rendering.