How to fetching Username-Password credentials in Jenkinsfile

withCredentials([usernamePassword(credentialsId: 'my-creds', usernameVariable: 'USERNAME', passwordVariable: 'PASSWORD')]) {
  // available as an env variable, but will be masked if you try to print it out any which way
  // note: single quotes prevent Groovy interpolation; expansion is by Bourne Shell, which is what you want
  sh 'echo $PASSWORD > tmp'
  // also available as a Groovy variable
  echo USERNAME
  // or inside double quotes for string interpolation
  echo "username is $USERNAME"
}