How to Determine if LCD Monitor is Turned on From Linux Command Line

Question

How do you tell if a computer\'s monitor(s) are turned on/off from the command line in Linux? I\'ve traditionally thought of monitors as output-only devices, but I\'ve noticed t

Answer 1

Not all monitors support vesa DDC. Thing might got even more complicated if you use a dock.

On the other hand, there is a way to check whether your actions are detected by monitoring the kernel/udev events. To do this, for Fedora and RHEL, type following command:

sudo udevadm monitor --property

It will display every kernel and udev events it detected. From that, you can try plug/unplug the monitor data cable; plug/unplug the monitor power cable; toggle the stand-by/on states by pressing the power button.

If no output is generated after an action, then your system cannot detect it.