: Thank you, that answeres all my questions in a nutshell.
Since it is a reasonable request, I thought about an easy way to customize at which light level(s) the light should be turned off. That will also streamline the script handling it. I am checking for existance of the turnlightoff file anyway, so checking against turnlightoffatlevelXX is basically the same (plus I don't need to check against the level again). But since you might end up with a total of 25 files, I will move those into a subdir.