!/bin/bash

function valid_ip() { local ip=$1 local stat=1

if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
    OIFS=$IFS
    IFS='.'
    ip=($ip)
    IFS=$OIFS
    [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
        && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
    stat=$?
fi

return $stat

echo "$stat"

}

ips=' 4.2.2.2 a.b.c.d 192.168.1.1 0.0.0.0 255.255.255.255 255.255.255.256 192.168.0.1 192.168.0 1234.123.123.123 '

for ip in $ips do RESULT=$( valid_ip $ip ) if [ $RESULT == 0 ]; then echo "$ip has result=$RESULT = good" else echo "$ip has result=$RESULT = bad" fi done