Script for PF firewall (which is used in *BSD systems), to automaticly add to table DYNAMIC current IP of domains domains. In crontab you should have a line similar to: */5 * * * * /scripts/dyndns.sh

dyndns.sh

#!/bin/sh

TABLE="DYNAMIC";
HOSTS="your-dynamic-domain.dyndns.org your-second-domain.dyndns.org";

for HOST in $HOSTS; do
  IP=`/usr/bin/host $HOST | cut -d " " -f 4`
	IPOLD=`/sbin/pfctl -t $TABLE -T show | grep -v "ALTQ" | tr -d " "`

	if [ "$IP" != "$IPOLD" ]; then
		/sbin/pfctl -t $TABLE -T delete $IPOLD
		echo "/sbin/pfctl -t $TABLE -T delete $IPOLD"
		/sbin/pfctl -t $TABLE -T add $IP
		echo "/sbin/pfctl -t $TABLE -T add $IP"
	fi
done

/sbin/pfctl -t DYNAMIC -T expire 43200