Don't forget to install dnsutils

The original

 ##############################################################################
 #
 #  application name: dnsactual
 #  other files: dnsactual.conf (keeps the last updated ip)
 #               dnsactual.log  (register date & time of the actualization)
 #  Author: Ernest Danton
 #  Date: 01/29/2007
 ­##############################################################################

 if test -f /etc/freedns/dnsactual.conf
   then
   CacheIP=$(cat /etc/freedns/dnsactual.conf)
 fi
 #echo $CacheIP
 CurreIP=$(wget http://freedns.afraid.org/dynamic/check.php -o /dev/null -O /dev/stdout | grep Detected | cut -d : -f 2 | cut -d '<' -
f 1 | tr -d " ")
 #echo $CurreIP
 if [ "$CurreIP" = "$CacheIP" ]
 then
   # Both IP are equal
   echo "Update not required..."
 else
   # The IP has change
   echo "Updating http://free.afraid.org with " $CurreIP
   wget http://freedns.afraid.org/dynamic/update.php?xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx -o /dev/null -O /dev/stdout
   echo `date`  "Updating log with IP " $CurreIP >> dnsactual.log
 fi
 rm -f /etc/freedns/dnsactual.conf
 echo $CurreIP > /etc/freedns/dnsactual.conf

This is what I worked it into

##############################################################################
#
#  application name: dnsactual. orginally from Ernest Danton 01/29/07
# 
#  I chaned it to to make more sense to me, but it is mostly the same
#  
#  
##############################################################################

echo `date`  "running dnsactual.sh "  >> /home/pi/freedns/dnsrun.log

CurreIP=$(wget http://freedns.afraid.org/dynamic/check.php -o /dev/null -O /dev/stdout | grep Detected | cut -d : -f 2 | cut -d '<' -f 1 | tr -d " ")
 
 echo $CurreIP > myip.conf
 DOMAIN="www.domain-name.org" 
 registered=$(nslookup $DOMAIN|tail -n2|grep A|sed s/[^0-9.]//g)
 echo $registered  >  /home/pi/freedns/dnslkup.txt

  if [ "$CurreIP" = "$registered" ]
then
 # Both IP are equal
   echo `date` "Update not required..Current IP " $CurreIP  > /home/pi/freedns/dnsactual.log
 else
   # The IP has change
   echo "Updating http://free.afraid.org with " $CurreIP
   wget http://freedns.afraid.org/dynamic/update.php?xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx -o /dev/null -O /dev/stdout
   echo `date`  "Updating log with IP " $CurreIP > /home/pi/freedns/dnsactual.log
   echo `date`  "Updating log with IP " $CurreIP >> /home/pi/freedns/dnschange.log
 fi