Bash script to check validate IP address

#!/bin/bash

# Test an IP address for validity:
# Usage:
#      is_ip IP_ADDRESS
#      if is_ip IP_ADDRESS; then return 1; else return 0; fi
#



is_ip(){

    input=$1
    octet1=$(echo $input | cut -d "." -f1)
    octet2=$(echo $input | cut -d "." -f2)
    octet3=$(echo $input | cut -d "." -f3)
    octet4=$(echo $input | cut -d "." -f4)
    stat=0

if [[ $input =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]] && [ $octet1 -le 255 ] && [ $octet2 -le 255 ] && [ $octet3 -le 255 ] && [ $octet4 -le 255 ];
  then
    stat=1
fi


echo "IP $input is $stat."

return  $stat

}

if [ -z $1 ];
  then
   echo "Usage: sh is_ip.sh IP_ADDRESS"
   exit 0
  else
   is_ip $1
fi
Ref: http://www.linuxjournal.com/content/validating-ip-address-bash-script