#!/bin/bash
 
bg_path=/home/username/day/
 
case $(date +%H) in
04 | 05 | 06 | 07 | 08 | 09 )
filename=sunrise.jpeg
;;
10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 )
filename=day.jpeg
;;
19 | 20 | 21 )
filename=sunset.jpeg
;;
* )
filename=night.jpeg
;;
esac
 
gconftool-2 -t string -s /desktop/gnome/background/picture_filename "$bg_path""$filename"
 
exit 0