title: Concatenate file name in pipeline steps script
body: <p>I am trying to concatenate a file name by appending strings and the build number within the steps script in my Jenkinsfile and then pass it to create a zipFile, but the environment build number does not get recognized in the concatenated string. What is the correct syntax?</p>
  
  <pre><code>stage ('Publish Reports') {
     steps {
        script {
           def fileName = "reportFiles/" + '${env.BUILD_NUMBER}' + ".zip"
           zip zipFile: fileName, archive: false, dir: 'target/site/main' 
        }
     }
  }
  </code></pre>
  
  <p>With this syntax, the fileName gets saved as:</p>
  
  <pre><code>reportFiles/${env.BUILD_NUMBER}.zip,
  </code></pre>
  
  <p>instead of the actual build number, for example :</p>
  
  <pre><code>reportFiles/1.zip
  </code></pre>