Bash script update he ipv6 tunnel info

HE.net ipv6 tunnel end

#!/bin/bash
#
#Script to update ip on Hurricane Electric every 30 minutes
#@author Aaron Ogle

#Variables
HE_userid=<userid>
HE_passwd=<passwordhash> #echo -n "yourpassword" | md5sum
HE_tunnelid=<tunnelid>

#Tossing it in a function
updateip() {
#Loop to keep IP updated
while [ true ]
   do

   #Get Current IP.
   NewIP=$(curl -s checkip.dyndns.org|sed -e 's/.*Current IP Address: //' -e 's/<.*$//')

   if [ "$OldIP" != "$NewIP" ]
   then
      curl -k -s "https://ipv4.tunnelbroker.net/ipv4_end.php?ipv4b=AUTO&pass=$HE_passwd&user_id=$HE_userid&tunnel_id=$HE_tunnelid" > /dev/null
      echo 'Updated IP:'$NewIP
   else 
       echo 'Unchanged'
    fi 

   #Sleep for 30 Minutes
   OldIP="$NewIP"
   sleep 1800

   done
}
#Calling it.  This is done so it can be added to the startup.
updateip &