read jenkins credentials (https://codurance.com/2019/05/30/accessing-and-dumping-jenkins-credentials/)

Jenkinsfile

pipeline {
  agent any
  stages {

    stage('usernamePassword') {
      steps {
        script {
          withCredentials([
            usernamePassword(credentialsId: 'gitlab',
              usernameVariable: 'username',
              passwordVariable: 'password')
          ]) {
            print 'username=' + username + 'password=' + password

            print 'username.collect { it }=' + username.collect { it }
            print 'password.collect { it }=' + password.collect { it }
          }
        }
      }
    }

    stage('usernameColonPassword') {
      steps {
        script {
          withCredentials([
            usernameColonPassword(
              credentialsId: 'gitlab',
              variable: 'userpass')
          ]) {
            print 'userpass=' + userpass
            print 'userpass.collect { it }=' + userpass.collect { it }
          }
        }
      }
    }

    stage('string (secret text)') {
      steps {
        script {
          withCredentials([
            string(
              credentialsId: 'joke-of-the-day',
              variable: 'joke')
          ]) {
            print 'joke=' + joke
            print 'joke.collect { it }=' + joke.collect { it }
          }
        }
      }
    }

    stage('sshUserPrivateKey') {
      steps {
        script {
          withCredentials([
            sshUserPrivateKey(
              credentialsId: 'production-bastion',
              keyFileVariable: 'keyFile',
              passphraseVariable: 'passphrase',
              usernameVariable: 'username')
          ]) {
            print 'keyFile=' + keyFile
            print 'passphrase=' + passphrase
            print 'username=' + username
            print 'keyFile.collect { it }=' + keyFile.collect { it }
            print 'passphrase.collect { it }=' + passphrase.collect { it }
            print 'username.collect { it }=' + username.collect { it }
            print 'keyFileContent=' + readFile(keyFile)
          }
        }
      }
    }

    stage('dockerCert') {
      steps {
        script {
          withCredentials([
            dockerCert(
              credentialsId: 'production-docker-ee-certificate',
              variable: 'DOCKER_CERT_PATH')
          ]) {
            print 'DOCKER_CERT_PATH=' + DOCKER_CERT_PATH
            print 'DOCKER_CERT_PATH.collect { it }=' + DOCKER_CERT_PATH.collect { it }
            print 'DOCKER_CERT_PATH/ca.pem=' + readFile("$DOCKER_CERT_PATH/ca.pem")
            print 'DOCKER_CERT_PATH/cert.pem=' + readFile("$DOCKER_CERT_PATH/cert.pem")
            print 'DOCKER_CERT_PATH/key.pem=' + readFile("$DOCKER_CERT_PATH/key.pem")
          }
        }
      }
    }

    stage('list credentials ids') {
      steps {
        script {
          sh 'cat $JENKINS_HOME/credentials.xml | grep "<id>"'
        }
      }
    }

  }
}