external online or not from bash

#!/bin/bash

# I run this from cron to be an independent "am I online or not", piping output to /tmp/netup

ext_ip=$(wget -q -O - checkip.dyndns.org | sed -e 's/[^[:digit:]|.]//g')
len_ext_ip=${#ext_ip}

#echo "$len_ext_ip"

if [ $len_ext_ip -gt 16 ]; then
    echo "0.0.0.0"
else
    echo "$ext_ip"
fi