Delete Jenkins build history

delete-jenkins-job-build-history.groovy

// change this variable to match the name of the job whose builds you want to delete
def jobName = "Your Job Name"
def job = Jenkins.instance.getItem(jobName)

job.getBuilds().each { it.delete() }
// reset the build number to 1
job.nextBuildNumber = 1
job.save()

def myjobs= [
'task_1':36,
'task_2':7,
'task_3':7,
'task_4':7
]

for (myjob in myjobs) {
Jenkins.instance.getItemByFullName(myjob.key).builds.findAll {
it.number <= myjob .value
}.each {
it.delete()
}
}