gmessage "Are you sure you want to shut down your computer?" -center -title "Take action" -font "Sans bold 10" -default "Cancel" -buttons "_Cancel":1,"_Log out":2,"_Reboot":3,"_Shut down":4 >/dev/null

case $? in
1)
echo "Exit";;
2)
killall openbox;;
3)
sudo shutdown -r now;;
4)
sudo shutdown -h now;;
esac