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 the Gnome Monitor Preferences dialog has a "detect monitor" function. Can this be generalized to determine if a monitor is physically turned off?
From systembash.com, here is the code taken from the link, in case it will be down some day:
#!/bin/bash
export DISPLAY=:0.0
if [ $# -eq 0 ]; then
echo usage: $(basename $0) "on|off|status"
exit 1
fi
if [ $1 = "off" ]; then
echo -en "Turning monitor off..."
xset dpms force off
echo -en "done.\nCheck:"
xset -q|grep "Monitor is"
elif [ $1 = "on" ]; then
echo -en "Turning monitor on..."
xset dpms force on
echo -en "done.\nCheck:"
xset -q|grep "Monitor is"
elif [ $1 = "status" ]; then
xset -q|sed -ne 's/^[ ]*Monitor is //p'
else
echo usage: $(basename $0) "on|off|status"
fi