Setting up auto display off during the night.

[greatm8nate]

It seems that in recent months the commands used to control HDMI out on the Raspberry Pi have changed. Most guides I’ve found online do not work anymore.

I just want to turn my display off at 8pm and turn it back on at 8am.
So I set up a cron job;

20 14 * * * pm2 stop mm 
21 14 * * * WAYLAND_DISPLAY="wayland-1" wlr-randr --output HDMI-A-1 --off
22 14 * * * WAYLAND_DISPLAY="wayland-1" wlr-randr --output HDMI-A-1 --on
23 14 * * * wlr-randr --output HDMI-A-1 transform 270
24 14 * * * pm2 start mm

The timing is one minute apart for testing.
Line 1 stops magic mirror.
Line 2 should turn the display off.
Line 3 turns it back on.
Line 4 correct the screen orientation to portrait (it is not saved).
Line 5 restarts the software.

That command on line 2 works when manually typed into the terminal, but the cron job cannot execute it for some reason. Here is the error log I collected for lines 2-4;

error: XDG_RUNTIME_DIR is invalid or not set in the environment.
failed to connect to display

As far as I have researched, the cron job is not in the same environment as me (the user), so it cannot execute this command. How to I make the cron job write as if I am typing the command into the terminal?

[karsten13]

@greatm8nate

looks like XDG_RUNTIME_DIR is unset, so you can check what value contains this variable in your user environment by executing echo $XDG_RUNTIME_DIR in the terminal and then change

WAYLAND_DISPLAY="wayland-1" wlr-randr --output HDMI-A-1 --off

to

XDG_RUNTIME_DIR="value-from-above" WAYLAND_DISPLAY="wayland-1" wlr-randr --output HDMI-A-1 --off