检测用户输入的一串数字是一个IP地址

#!/bin/bash


printerr () {
        echo "incorrect IP format."
        readip
        chkip
}

readip () {
        read -p "Your IP: " IP
}

chkip () {
        echo "$IP" | grep -Eq '[^0-9.]|^\.|\.$|^0*\.|\.\.' && printerr
        [ $(echo -e "${IP//./\n}" | wc -l) -ne 4 ] && printerr
        for i in ${IP//./ } ; do
                echo $i | grep -Eq "^0+[^0]" && printerr
                [ $((10#$i/8)) -gt 31 ] && printerr

        done
}

if [ "$1" ]; then
        IP=$1
else
        readip
fi
chkip
echo "$IP is good!"