Cancel all running Jenkins builds with system groovy script

jenkins cancel running builds

import jenkins.model.Jenkins

def numCancels = 0;
Jenkins.instance.getAllItems(Job.class).each{ 
  def job = it
  for (build in job.builds) {
    if (build.isBuilding()) { build.doStop(); numCancels++; }
  }  
}

println("${numCancels}");