Jenkins script to replace all job labels from one value to another

jenkins-replace-job-labels.groovy

String oldLabel = 'foo'
String newLabel = 'bar'
boolean dryRun = true

for (item in Jenkins.instance.getAllItems(Job.class).findAll{it.hasProperty('assignedLabel')}) {
  if (oldLabel == item.assignedLabel.toString()) {
    println "${item.name}: label being updated from '${oldLabel}' to '${newLabel}'"
    if (!dryRun) {
      item.setAssignedLabel(new hudson.model.labels.LabelAtom(newLabel))
    }
  }
}