Gnome 2.3 on Ubuntu 10.04 LTS (Lucid Lynx) doesn’t appear to have an automatic wallpaper changer built in. While it appears there are many ways to accomplish this, I decided to write my own little script to get some time in with bash… alternative ways I have found include using “Wallpaper-tray” (which doesn’t appear to be in 10.04), Desktop Drapes, or a variation of the script below using things like “gconftool-2“.

To use this script, do the following:

• Right-click on the desktop and choose “Change Desktop Background“
• Look through the backgrounds, and make sure the ones listed are the ones you want to have the script randomly select
• Open up a text file using “gedit“, and add the contents of the script:

  #!/bin/bash
  installedDir=~/Pictures/backgrounds/random
  i=0
  while read line; do
     data=`echo "${line}" | grep -i filename`
     if [ "$data" != "" ]; then
        filenameCutLength=$((${#data}-11))
        filename=$(echo $data | cut -b11-$filenameCutLength)
        if [ "$filename" != "(none)" ] || [ "$filename" != 
        "random.img" ]; then
           extension=$(echo ${filename,,} | 
           cut -b$(expr ${#filename} - 2)-${#filename})
           if [ "$extension" == "jpg" ] || [ "$extension" 
           == "png" ] || [ "$extension" == "svg" ]; then
              fileArray[$i]=$(echo $filename)
              i=$(expr $i + 1)
           fi
        fi
     fi
  done << EOF
     $(grep deleted="false -A7 ~/.gnome2/backgrounds.xml)
  EOF
  fileArrayLength=`echo $[ ( $RANDOM % ${#fileArray[@]} ) ]`
  cp "${fileArray[$fileArrayLength]}"
  "$installedDir/random.img"

• Save the file as “gRandomBackground.sh” in a directory (this example uses: “/home/$USER/Pictures/backgrounds/random”, if you install it elsewhere, be sure to change the $installedDir variable in the script)
• Open “Terminal” and enter the command: crontab -e If you haven’t used crontab before, stick with the default, “nano“
• Paste the following as one line into the editor: 0 */3 * * * bash ~/Pictures/backgrounds/random/gRandomBackground.sh This will change the background every three hours, on the hour. “Ctrl+O, and then Ctrl+W” should get the crontab saved and also get you exited out of nano. For more information on how to use cron, see Google.
• Open up the “Appearance Preferences” dialog again, by right-clicking on the desktop and selecting “Change Desktop Background“
• Click the “Add…” button and browse to the directory that gRandomBackground.sh is installed to
• Select the “random.img” background, click the “Open” button, and then the “Close” button

Your background should change every three hours.