Ubuntu – Background not changing using gsettings from cron

cronenvironment-variablesgnomegsettings

I'm trying to change my wallpaper to a random image using Indrajith Indraprastham's suggested script here:
How to change desktop background from command line in Unity?

When I run the script from a terminal window, the bg changes just fine, but when it's run from cron, I'm mailed this error:

(process:21901): dconf-WARNING **: failed to commit changes to dconf: Error spawning command line 'dbus-launch –autolaunch=00216c114dcf433c9bb9009985d607d6 –binary-syntax –close-stderr': Child process exited with code 1

I would appreciate any suggestions.

Best Answer

  • Editing gsettings from cron; missing environment variable

    If you run the script from your own environment (e.g. from a terminal window or from Startup Applications), a number of environment variables will be set. cron however runs your script with a limited set of environment variables.

    To edit gsettings successfully from cron, you need to set the DBUS_SESSION_BUS_ADDRESS environment variable. You can do that by adding two lines to your script, as described here (and below).

    Your script, including setting the needed variable

    The script from here, edited to include the DBUS_SESSION_BUS_ADDRESS environment variable, then becomes:

    #!/bin/bash
    
    PID=$(pgrep gnome-session)
    export DBUS_SESSION_BUS_ADDRESS=$(grep -z DBUS_SESSION_BUS_ADDRESS /proc/$PID/environ|cut -d= -f2-)
    
    DIR="/home/indra/Pictures/wallpapers"
    PIC=$(ls $DIR/* | shuf -n1)
    gsettings set org.gnome.desktop.background picture-uri "file://$PIC"
    

    Related: Running .sh every 5 minutes