#!/bin/bash

NS="127.0.0.1"
NSKEY="/etc/bind/ddns-key.blackgate.org.conf"
TMPFILE="/var/www/html/new_dynamic_ip.txt"
ZONE="blackgate.org"
TIMEOUT=60

OLDIP=$(dig @$NS $ZONE A | grep ^$ZONE.*A | awk '{ print $5 }')
NEWIP=$(cat $TMPFILE)

echo "old: $OLDIP"
echo "new: $NEWIP"

if [ "$OLDIP" != "$NEWIP" ]; then
       echo -e "
       update delete $ZONE. A
       update add $ZONE. $TIMEOUT A $NEWIP
       show
       send" | /usr/bin/nsupdate -k $NSKEY
       rndc freeze $ZONE
       rndc thaw $ZONE
else
       echo "no update required"
fi