#!/bin/sh
clear


printf "ip address?: "
read ip

ipchk=`ifconfig | grep "$ip"`

if [ $ipchk ] ; then
  echo "Valid Ip."
else
  echo "Invalid Ip"
  printf "ip address?: "
  read ip
fi

## TEST Results ##

# get-test
  ip address?: 45
  [: inet: unexpected operator
  Invalid Ip
  ip address?: 208.74.173.173
#