Can I make a screen switch from one computer to another by cli?

Question

I have my monitor hooked up to computer A via DVI and to computer B via VGA. If I start PC A first and PC B last, the monitor displays PC A's signal.

Is there an easy way to change between the two signals via the command line such that the monitor displays the signal of the desired PC without me having to unplug the monitor?

Answer 1

If making the screen sleep works, then almost certainly the toggle- script below will work:

#!/bin/bash
# --- set your monitor below
monitor=VGA-0
# ---
if [ -z "$(xrandr | grep $monitor | grep +)" ]; then
  xrandr --output $monitor --auto
else
  xrandr --output $monitor --off
fi

The script toggles on/off a monitor, to be set in the head of the script:

# --- set your monitor below
monitor=VGA-0
# ---

How to use

1. Copy the script into an empty file, save it as screentoggle.sh
2. In the head of the script, set the monitor, like in the example. Use xrandr to find the name of your monitor

3. Add the script to a shortut key: Choose: System Settings > "Keyboard" > "Shortcuts" > "Custom Shortcuts". Click the "+" and add the command:

   sh /path/to/screentoggle.sh
   

Now if you toggle the screen off on one computer, it will be available on the other.

Note

You probably need to add (and run) the shortcut on both computers, since the screen will only switch if the screen is set to --auto on at least one computer.

Answer 2

How about xset dpms force standby which just does the obvious, turns the display off (there are options of on, off, standby, suspend).
You can simply use the reverse xset dpms force on to resume; you could have a script linking via ssh to turn the other PC's display on/off as required:
xset dpms force standby; ssh other_pc xset dpms force on