cron=
while [ "$cron" != "yes" ] && [ "$cron" != "no" ]; do
echo "Cron-oikeudet? yes/no"
echo "default on yes"
read cron
[ "z$cron" = "z" ] && cron="yes"
if [ "$cron" != "yes" ] && [ "$cron" != "no" ] then echo "Not understood."    
done