gistfile1.txt

#!/bin/bash

# Test an IP address for validity:
# Usage:
#      valid_ip IP_ADDRESS
#      if [[ $? -eq 0 ]]; then echo good; else echo bad; fi
#   OR
#      if valid_ip IP_ADDRESS; then echo good; else echo bad; fi
#
total=0
num=1

function valid_ip()
{
   local  ip=$1
   local  stat=1

   if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
       OIFS=$IFS
       IFS='.'
       ip=($ip)
       IFS=$OIFS
       [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
           && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
       stat=$?
   fi
   return $stat
}

# If run directly, execute some tests.
if [[ "$(basename $0 .sh)" == 'valid_ip' ]]; then
   ips='
       8.8.8.8
       INTERNAL IP 1
       INTERNAL IP 2
       '
   for ip in $ips
   do
       if valid_ip $ip; then stat='good'; else stat='bad'; fi
         if state='good'; then total=$(($total + $num)) ; fi
   done
fi

if [[ $total == 3 ]]; then
 echo "All is ok";
 exit 0; else
 echo "OOPS issues ongoing";
 exit 1
fi