title: Use cloudformation parameter in userdata
body: <p>I have  zookeeper connect as   ip1:port1,ip2:port2,ip3:port3 and I want to use this in my userdata How can i do it?</p>
  
  <pre><code>"ZooKeeperConnect": {
           "Type": "String",
           "Description": "list of IP or CNAME's for the associated zookeeper ensemble",
           "AllowedPattern": "([1-9][0-9]?|[1-2][0-9]{2})(\\.([1-9][0-9]?|[1-2][0-9]{2})){3}(:[1-9][0-9]{1,4})?(,([1-9][0-9]?|[1-2][0-9]{2})(\\.([1-9][0-9]?|[1-2][0-9]{2})){3}(:[1-9][0-9]{1,4})?)*"
         }
  
  
  "UserData": {
           "Fn::Base64": {
             "Fn::Join": [
               "",
               [
                 "#!/bin/bash \n",
                 "echo Cache proxy vars... \n",
  </code></pre>
  
  <p>I want to use ZooKeeperConnect  values  in  my userdata</p>