decrypt credentials files in jenkins

decrypt-credentials-file-jenkins.groovy

import com.cloudbees.plugins.credentials.*;
import com.cloudbees.plugins.credentials.domains.Domain;
import org.jenkinsci.plugins.plaincredentials.impl.FileCredentialsImpl;

def jenkins_credentials_id = "my-jenkins-credentials-file-id"
SystemCredentialsProvider.getInstance().getCredentials().stream().
  filter { cred -> cred instanceof FileCredentialsImpl }.
    map { fileCred -> (FileCredentialsImpl) fileCred }.
      filter { fileCred -> jenkins_credentials_id.equals( fileCred.id ) }.
        forEach { fileCred ->
          String s = new String( fileCred.getSecretBytes().getPlainData() )
          println(s)
        }