#!/bin/sh
newip=`wget -o /dev/null -O - http://simple.showmyip.com | cut -f1 -d' ' | sed -n 1p`
presentip=`host myweb.com | sed -n 1p | cut -d' ' -f4`
if [ "$newip" != "$presentip" ]; then update_dns_ip.sh; fi

Useful if you are behind a router, or in a LAN, and you didn't make (or can't have) a  direct ppp connection to the ISP.
Change "myweb.com" to the correct hostname
For example to update zoneedit zone:
#update_dns_ip.sh
wget -O - --http-user= --http-passwd= 'http://dynamic.zoneedit.com/auth/dynamic.html?host='
(complete user, pass and host)

Dynamic IP update (to DNS service like zoneedit or dyndns) inside a local LAN or behind a router

linux, ip

Bash