Return the host's path of a Jenkins WORKSPACE running a docker container.

hostWorkspace.groovy

import groovy.json.JsonSlurper;

def call(String workspace) {
  def p = ['/bin/bash', '-c', '''
docker ps --no-trunc --all \
  | grep `cat /etc/hostname` \
  | grep jenkins.sh \
  | awk '{print $1}' \
  | xargs docker inspect
'''].execute()
  p.waitFor();
  def o = new JsonSlurper().parseText(p.text)
  def source = o[0].Mounts.find { it.Destination == "/var/jenkins_home" }.Source
  return workspace.replace("/var/jenkins_home", source)
}