Linux Desktop Hacks

Randomize Your GNOME Wallpaper #45

Chapter 6, GNOME Desktop Hacks

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151

HACK

The line let "NUMBER %= TOTAL" is the part that actually selects which image

will be used. This line divides the randomly generated number by the num-

ber of images in the directory and stores the remainder of this division in the

$NUMBER variable. If you’re wondering how this works, the remainder must

be between 0 and 1, minus the number of images, and because in the next

part the script starts counting from 0, it is possible for any image to be

selected with this method.

The final part of the script simply counts through each image to see if it is the

one that was selected. When it finds the correct image, it modifies the GConf

setting that stores the filename of the wallpaper using the

gconftool com-

mand (this might be

gconftool-2 on some systems). Nautilus notices this

change immediately and updates the wallpaper. So, here’s the final script:

#!/bin/bash

export DIR='/home/adam/Images/Wallpapers/'

export NUMBER=$RANDOM

export TOTAL=0

for f in `ls $DIR`

do

let "TOTAL += 1"

done

let "NUMBER %= TOTAL"

export CURRENT=0

for f in `ls $DIR`

do

if [ $CURRENT = $NUMBER ]

then

/usr/bin/gconftool-2 -t string -s /desktop/gnome/background/picture_

filename $DIR/$f

break

fi

let "CURRENT += 1"

done

Save the script somewhere convenient such as /home/foo/setbg.sh. Also make

it executable by running the following in a terminal:

foo@bar:~$ chmod +x ...