RESOLV=/home/syed/shellscript/resolv.conf
exec <$RESOLV >$RESOLV.new

while read line ; do 
   echo "# $line"
done

echo search.example.com
echo nameserver xxx.xxx.xxxx.xxxx
echo nameserver yyy.yyy.yyyy.yyyy

exec >-
mv $RESOLV $RESOLV.$$.bak 
mv $RESOLV.new $RESOLV