DynDNS update script for occasionally changing IPs

do-dyndns.sh

#!/bin/sh
cd `dirname $0`
exec >>dyndns.log 2>&1
LANG=C
export LANG
date
ip=`/sbin/ifconfig eth3 | sed -ne 's,^.*inet addr:\([0-9.]*\) .*$,\1,p'`
echo ip: $ip
if test X"`cat ip`" = X"$ip"; then
	echo Same addr
else
	echo Diff addr
	rm -f tag
fi
if test X`find tag -mtime -28` = X; then
  touch tag
  /usr/bin/wget --no-check-certificate -O - https://yourname:[email protected]/nic/update?hostname=youraddr.ath.cx | cat
fi
echo $ip >ip