Chapter 21: Jenkins Pipeline and Jenkinsfile

21.13 Stash, approval, and currentBuild

By Ravindra Bagale · Last updated: 25 October 2026

Why: the problem

Big pipelines use many agents. Think of Zomato. The build runs on a fast Linux agent. Tests run on another. The live copy runs on a special deploy agent. Files do not travel between agents by themselves. stash and unstash carry them. Then there is control. Before a change reaches production, a lead often must say yes. The input step pauses the pipeline and shows a button. Only allowed people can click it. Finally, currentBuild tells you about the build itself: result, number, time, and the changes it contains. You use it for messages and decisions. In this lesson you will pass dist between two agents, add an approval with a time limit, and print a clear summary from currentBuild.

What we will build

You will build on one agent, stash dist, and unstash it on another. You will add an approval step limited to a lab-leads group with a 10 minute limit. You will print a build summary and set the build description.

What: every term in plain English

• stash — Saves files from the workspace in the controller for this build.
• unstash — Restores stashed files in another stage or agent.
• input — Pauses and asks a person to approve.
• submitter — Users or groups allowed to approve.
• currentBuild — Object with result, number, duration and changes of this build.
• currentBuild.description — Text shown under the build number.
• UNSTABLE — Result when tests fail but the build itself worked, set by junit.
• agent none with input — Approval should not hold an executor while waiting.

How: step by step

1. Write the build stage

   stash name: "dist", includes: "dist/**"
   

   What it does: Saves the output.

   Output

   Stashed 1 file(s)
   

2. Unstash in Live

   unstash "dist"
   

   What it does: Gets the same files on the deploy agent.

   Output

   (files restored)
   

3. Add approval

   input message: "Copy to lab live?", submitter: "lab-leads"
   

   What it does: Pauses for a lead.

   Output

   Copy to lab live?
   Proceed or Abort
   

4. Approve

   Click Proceed as a lab-leads user
   

   What it does: The pipeline continues.

   Output

   Approved by asha
   

5. Print summary

   echo currentBuild fields
   

   What it does: Shows result and time.

   Output

   Build 14 SUCCESS in 2 min 3 sec
   

6. Set description

   currentBuild.description = "..."
   

   What it does: Shows commit on the job page.

   Output

   #14 commit 4b2d9e1
   

Example 1: Stash on one agent, unstash on another

Stack. Jenkins stash

Goal. Stash on one agent, unstash on another.

Jenkinsfile

pipeline {
  agent none
  stages {
    stage('Build') {
      agent { label 'node20' }
      steps {
        sh 'npm ci && npm run build'
        stash name: 'dist', includes: 'dist/**'
      }
    }
    stage('Live') {
      agent { label 'deploy' }
      steps {
        unstash 'dist'
        sh 'ls -l dist && hostname'
      }
    }
  }
}

What each line does

• agent none — Each stage picks an agent.
• stash name: 'dist' — Saves dist for this build only.
• unstash 'dist' — Restores it on the deploy agent.
• Size limit — Stash is for small files. Use artifacts or a registry for big ones.

Green output

[Pipeline] stage (Build)
Running on agent-node20
build done: dist/index.html
Stashed 1 file(s)
[Pipeline] stage (Live)
Running on agent-deploy
+ ls -l dist
-rw-r--r-- 1 jenkins jenkins 31 Oct 25 11:20 index.html
+ hostname
deploy-01
Finished: SUCCESS

Expected result. The file moved from agent-node20 to deploy-01.

Example 2: Approval with a time limit, not holding an agent

Stack. Jenkins input

Goal. Approval with a time limit, not holding an agent.

Jenkinsfile

pipeline {
  agent none
  stages {
    stage('Approve') {
      options { timeout(time: 10, unit: 'MINUTES') }
      input {
        message 'Copy badge to lab live?'
        ok 'Yes, copy'
        submitter 'lab-leads'
        parameters { string(name: 'NOTE', defaultValue: 'ok', description: 'Why') }
      }
      steps { echo "Approved. Note: ${NOTE}" }
    }
    stage('Live') {
      agent { label 'deploy' }
      steps { echo 'copying' }
    }
  }
}

What each line does

• stage input block — Waits before the stage runs, with no agent held.
• submitter 'lab-leads' — Only this group can approve.
• timeout 10 min — If nobody clicks, the build aborts.
• parameters in input — The approver can type a note.

Green output

[Pipeline] stage (Approve)
[Pipeline] input
Copy badge to lab live?
Yes, copy or Abort
Approved by asha
Approved. Note: release badge v1
[Pipeline] stage (Live)
copying
Finished: SUCCESS

Expected result. A human said yes, with a note, before Live. No executor was wasted while waiting.

Example 3: Build summary with currentBuild

Stack. Jenkins currentBuild

Goal. Build summary with currentBuild.

Jenkinsfile

pipeline {
  agent any
  stages {
    stage('Test') { steps { sh 'npm ci && npm test' } }
  }
  post {
    always {
      script {
        def short = env.GIT_COMMIT ? env.GIT_COMMIT.take(7) : 'none'
        currentBuild.description = "commit ${short}"
        echo "Build ${currentBuild.number} ${currentBuild.currentResult} in ${currentBuild.durationString}"
        echo "Previous: ${currentBuild.previousBuild?.result}"
        for (cs in currentBuild.changeSets) {
          for (e in cs.items) { echo "Change: ${e.author} ${e.msg}" }
        }
      }
    }
  }
}

What each line does

• currentBuild.description — Shown on the job page under the build.
• take(7) — Short commit id.
• durationString — Human readable time.
• previousBuild?.result — Result of the last build; ?. avoids an error on build 1.
• changeSets — Commits in this build.

Green output

Build 15 SUCCESS in 21 sec and counting
Previous: FAILURE
Change: Asha Patil fix badge text
Finished: SUCCESS

Expected result. You can tell the team: fixed, previous was red, here is the change.

Example 4: Keep files after the build with archive and copy them to another job

Stack. Copy Artifact plugin

Goal. Keep files after the build with archive and copy them to another job.

Jenkinsfile (build job)

pipeline {
  agent any
  stages {
    stage('Build') {
      steps {
        sh 'npm ci && npm run build && tar czf badge-dist.tgz dist'
      }
    }
  }
  post { success { archiveArtifacts artifacts: 'badge-dist.tgz', fingerprint: true } }
}

Jenkinsfile (deploy job)

pipeline {
  agent { label 'deploy' }
  stages {
    stage('Get build') {
      steps {
        copyArtifacts projectName: 'badge-scm', selector: lastSuccessful(), filter: 'badge-dist.tgz'
        sh 'tar xzf badge-dist.tgz && ls dist'
      }
    }
  }
}

What each line does

• tar czf — One file is easier to move than many.
• archiveArtifacts — Kept on the build page after the build ends.
• copyArtifacts — From the Copy Artifact plugin. Pulls a file from another job.
• lastSuccessful() — Takes the newest green build.

Green output

[Pipeline] copyArtifacts
Copied 1 artifact from "badge-scm" build number 15
+ tar xzf badge-dist.tgz
+ ls dist
index.html
Finished: SUCCESS

Expected result. stash is for one build. archive plus copyArtifacts is for passing files between jobs.

Verify: did it work?

1. See the description

   Job page > Build History
   

   What it does: Shows commit text.

   Output

   #15 commit 4b2d9e1
   

2. See who approved

   Build > Paused for Input or console
   

   What it does: Name of the approver.

   Output

   Approved by asha
   

When it is red 1

No such saved stash 'dist'

Cause. unstash name differs or Build stage failed before stash.

Fix, step by step

1. Match the names.
2. Check Build passed.

When it is red 2

Build is waiting for input forever

Cause. No timeout on the input stage.

Fix, step by step

1. Add timeout in stage options.

When it is red 3

asha is not allowed to approve

Cause. The user is not in submitter.

Fix, step by step

1. Add the user or group.
2. Check group names.

When it is red 4

Scripts not permitted to use method ... getChangeSets

Cause. Sandbox blocked a method.

Fix, step by step

1. Ask admin to review in Script Approval.

Cleanup

1. Clear stashes

   They are deleted at build end automatically
   

   What it does: Nothing to do.

   Output

   (automatic)
   

2. Delete practice builds

   Build > Delete build
   

   What it does: Clean history.

   Output

   Deleted
   

Practice tasks

Homework: try at home

Recap

• stash and unstash move small files.
• input pauses for approval.
• Use submitter and timeout with input.
• Do not hold an agent while waiting.
• currentBuild gives result, time and changes.

FAQ

Is stash kept after the build?

No. Use archiveArtifacts for that.

Can input ask questions?

Yes, with parameters inside input.

Can I approve from Slack?

Some plugins allow it, but the click still goes to Jenkins.

What is UNSTABLE?

Tests failed but the build ran, often set by junit.

How big can a stash be?

Keep it small, under about 100 MB.

Interview questions

1. How do you pass files between stages on different agents?

   stash in one stage and unstash in another.

2. How do you add a manual approval?

   An input block at stage level with submitter and a timeout, with agent none so no executor waits.

3. What is currentBuild?

   A global with the build result, number, duration, description and changes.

4. stash vs archiveArtifacts?

   stash is temporary for one build; archive keeps files on the build page.

5. Approval stuck for days. Fix?

   Add a timeout to the input stage.

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