IP address update script for ieServer.Net

#!/bin/sh
#
# ieserverupdate
#
# Description : IP address update script for ieServer.Net
# Update      : 2012/10/11
# Autor       : yuch4n
#

#########################
# Settings
USER=
PASS=
DOMAIN=
IPFILE=~/current_ip
#########################

IPCHKURL=http://ieserver.net/ipcheck.shtml
UPDATEURL=https://ieserver.net/cgi-bin/dip.cgi
[ -z ${USER} ] || [ -z ${PASS} ] || [ -z ${DOMAIN} ] || [ -z ${IPFILE} ] && echo 'Setting is not correct' && exit 1
[ -f ${IPFILE} ] && CURRENT_IP=`cat ${IPFILE}`
NEW_IP=`wget -q -O - ${IPCHKURL}`
[ -z ${CURRENT_IP} ] && echo ${NEW_IP} > ${IPFILE} && exit 0
if [ ${CURRENT_IP} != ${NEW_IP} ]; then
    wget --post-data "username=${USER}&domain=${DOMAIN}&password=${PASS}&updatehost=1" -q -O - ${UPDATEURL} > /dev/null
    if [ $? -eq 0 ]; then
        echo ${NEW_IP} > ${IPFILE}
        logger ${USER}.${DOMAIN} updated ${CURRENT_IP} to ${NEW_IP}
    else
        logger ${USER}.${DOMAIN} update aborted ${CURRENT_IP} to ${NEW_IP}
    fi
fi
exit 0