Jenkins Declarative Pipeline: How to inject properties

Question

I have Jenkins 2.19.4 with Pipeline: Declarative Agent API 1.0.1. How does one use readProperties if you cannot define a variable to assign properties read to?

For e

Answer 1

The @jon-s solution requires granting script approval because it is setting environment variables. This is not needed when running in same stage.

pipeline {
  agent any
  stages {
    stage('A') {
      steps {
        writeFile file: 'props.txt', text: 'foo=bar'
        script {
           def props = readProperties file:'props.txt';
        }
        sh "echo $props['foo']"
      }
    }
  }
}