title: How to use `jq` to obtain the keys
body: <p>My json looks like this : </p>
  
  <pre><code>{
    "20160522201409-jobsv1-1": {
      "vmStateDisplayName": "Ready",
      "servers": {
        "20160522201409 jobs_v1 1": {
          "serverStateDisplayName": "Ready",
          "creationDate": "2016-05-22T20:14:22.000+0000",
          "state": "READY",
          "provisionStatus": "PENDING",
          "serverRole": "ROLE",
          "serverType": "SERVER",
          "serverName": "20160522201409 jobs_v1 1",
          "serverId": 2902
        }
      },
      "isAdminNode": true,
      "creationDate": "2016-05-22T20:14:23.000+0000",
      "totalStorage": 15360,
      "shapeId": "ot1",
      "state": "READY",
      "vmId": 4353,
      "hostName": "20160522201409-jobsv1-1",
      "label": "20160522201409 jobs_v1 ADMIN_SERVER 1",
      "ipAddress": "10.252.159.39",
      "publicIpAddress": "10.252.159.39",
      "usageType": "ADMIN_SERVER",
      "role": "ADMIN_SERVER",
      "componentType": "jobs_v1"
    }
  }
  </code></pre>
  
  <p>My key keeps changing from time to time. So for example <code>20160522201409-jobsv1-1</code> may be something else tomorrow. Also I may more than one such entry in the json payload.</p>
  
  <p>I want to <code>echo $KEYS</code> and I am trying to do it using <code>jq</code>.</p>
  
  <p>Things I have tried : 
  <code>| jq .KEYS</code> is the command i use frequently. </p>
  
  <p>Is there a jq command to display all the primary keys in the json?</p>
  
  <p>I only care about the <code>hostname</code> field. And I would like to extract that out. I know how to do it using <code>grep</code> but it is NOT a clean approach.</p>