Is there a way to query the power status of an Xorg/X11 display from command line? I want to know if my laptop LCD is powered on after the screen saver–apparently the backlight is still on. This is despite my gnome-screensaver-preferences setting that after 5 minutes of idling, the display is supposed to go to sleep. I am using Debian 6 and whatever x server comes with it.
I see that upower utility has some nifty switches, but they are not documented.
Best Answer
To test whether your monitor is on or off you can use
In order to determine the brightness of your LCD backlight you can run