Shell check IP

#! /bin/bash

checkip() {
        if echo $1 |egrep -q '^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$' ; then
                a=`echo $1 | awk -F. '{print $1}'`
                b=`echo $1 | awk -F. '{print $2}'`
                c=`echo $1 | awk -F. '{print $3}'`
                d=`echo $1 | awk -F. '{print $4}'`

for n in $a $b $c $d; do
                        if [ $n -ge 255 ] || [ $n -le 0 ]; then
                                echo 'bad ip(2)!'
                                return 2
                        fi
                done
        else
                echo 'bad ip(1)!'
                return 1
        fi
}

echo -n "Please input the ip:"
read  ip
checkip  $ip