title: How to get UID in Jenkins Pipeline job
body: <p>How to access <code>UID</code> variable in Jenkins pipeline job?</p>
  
  <p>I got <code>null</code> when do:</p>
  
  <pre class="lang-groovy prettyprint-override"><code>pipeline {
  
      agent any
      environment {
          def userId = "${env.UID}";
      }
      stages {
          stage('Print UID') { 
              steps {
                  script {
                     echo "${userId}"
                  }
              }
          }
      }
  }
  </code></pre>
  
  <p>Jenkins is hosted on Ubuntu 16.04</p>