
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 ...