Stash and unstash for passing data in Jenkins - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this Jenkins pipeline snippet?

Consider this Jenkins pipeline stage snippet using stash and unstash:

stage('Build') {
  steps {
    writeFile file: 'app.txt', text: 'version 1.0'
    stash name: 'appFiles', includes: 'app.txt'
  }
}
stage('Test') {
  steps {
    unstash 'appFiles'
    script {
      def content = readFile('app.txt')
      echo content
    }
  }
}

What will be printed in the Test stage?

A Error: No such file 'app.txt'

B version 1.0

C Empty output

D version 2.0

💡 Hint

Remember that stash saves files from one stage and unstash restores them in another.

The 'app.txt' file is created and stashed in the Build stage. The Test stage unstashes it, so reading 'app.txt' prints its content 'version 1.0'.

🧠 Conceptual

intermediate

Why use stash and unstash in Jenkins pipelines?

Which of the following best explains the purpose of stash and unstash in Jenkins pipelines?

A To pass files between different stages or nodes during a pipeline run

B To permanently save files to the Jenkins master workspace

C To create backups of the entire Jenkins workspace

D To deploy files directly to production servers

💡 Hint

Think about how pipeline stages might run on different machines or agents.

Stash and unstash allow temporary storage and transfer of files between pipeline stages or nodes, enabling sharing of build artifacts.

❓ Troubleshoot

advanced

Why does unstash fail with 'No such stash' error?

You have this Jenkins pipeline snippet:

stage('Build') {
  steps {
    writeFile file: 'output.log', text: 'log data'
    stash name: 'logs', includes: 'output.log'
  }
}
stage('Deploy') {
  steps {
    unstash 'logfiles'
  }
}

When running, the Deploy stage fails with:
No such stash 'logfiles'
What is the most likely cause?

A The Deploy stage runs on a different node that cannot access the stash

B The file 'output.log' was not created before stashing

C The stash command must be inside the same stage as unstash

D The stash name used in unstash does not match the stash name used in stash

💡 Hint

Check the exact names used in stash and unstash commands.

The stash was saved with the name 'logs' but unstash tries to retrieve 'logfiles', causing the error.

🔀 Workflow

advanced

Identify the correct sequence to share files between stages using stash/unstash

You want to share a file created in the 'Compile' stage with the 'Test' stage in a Jenkins pipeline. Which sequence of steps is correct?

A Compile stage: unstash file; Test stage: create file, stash it

B Compile stage: create file; Test stage: read file without unstash

C Compile stage: create file, stash it; Test stage: unstash file, read it

D Compile stage: create file; Test stage: stash file, then unstash it

💡 Hint

Remember stash saves files and unstash restores them in later stages.

Files must be created and stashed in the first stage, then unstashed in the next stage to be accessible.

✅ Best Practice

expert

What is the best practice when using stash to pass large files between Jenkins pipeline stages?

When passing large files between stages using stash and unstash, which practice helps avoid performance issues?

A Only stash the necessary files using the 'includes' pattern to minimize data size

B Always stash the entire workspace to ensure all files are available

C Use unstash multiple times in the same stage to improve speed

D Avoid using stash and unstash; copy files manually between nodes

💡 Hint

Think about how much data is transferred and stored temporarily.

Stashing only needed files reduces data transfer and storage, improving pipeline speed and resource use.