shell 验证ip

#!/bin/bash

function isIp(){
       IP=$1
        if [ `echo $IP | awk -F . ‘{print NF}‘` -ne 4 ];then
                echo "Wrong IP!"
                exit 2
        else
                a=`echo $IP | awk -F . ‘{print $1}‘`
                b=`echo $IP | awk -F . ‘{print $2}‘`
                c=`echo $IP | awk -F . ‘{print $3}‘`
                d=`echo $IP | awk -F . ‘{print $4}‘`
                if [[ $a -gt 0 && $a -le 255 ]] && [[ $b -ge 0 && $b -le 255 ]] && [[ $c -ge 0 && $c -le 255 ]] && [[ $d -gt 0 && $d -lt 255 ]];then
                        #echo "Right IP!"
                        return 0
                        exit
                else
                       # echo "Wrong IP!"
                       return 2
                fi
        fi

}

isIp "192.168.1.902"