#!/usr/bin/ruby                                                      

require 'resolv'

puts "Ener a new IP Address"
  ip_change = nil
  loop do
    ip_change = gets.chomp
    case ip_change
    when Resolv::IPv4::Regex
      break
    end
  cmd=`/sbin/ifconfig eth0 #{ip_change}`
  puts "OK. The new IP address for eth0 is #{ip_change}\n"
end