Assign label to all jobs in jenkins

jenkins_label_assigned.groovy

import hudson.model.*
import hudson.model.labels.*
import hudson.maven.*
import hudson.tasks.*
import hudson.plugins.git.*

hudsonInstance = hudson.model.Hudson.instance
allItems = hudsonInstance.allItems
buildableItems = allItems.findAll{ job -> job instanceof BuildableItemWithBuildWrappers }

buildableItems.each { item ->
  boolean shouldSave = false
  item.allJobs.each { job ->
    job.assignedLabel = new LabelAtom('<label-name>') 
  }
}