What are Jenkins shared libraries?

Short answer

Jenkins shared libraries are repositories containing reusable pipeline code. They allow teams to standardize build logic and reduce duplication across projects.

Steps

1. Create a Git repository with the library code.
2. Define functions in vars/ or classes in src/.
3. Configure the library in Jenkins system settings.
4. Import and use it in a Jenkinsfile.

Example

// vars/buildApp.groovy
def call(String version) {
    sh "docker build -t myapp:${version} ."
}

Usage:

@Library('my-shared-library') _
pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                buildApp('1.0')
            }
        }
    }
}

Tips

• Version libraries with Git tags.
• Document library functions for consumers.
• Use unit tests for library code.

Common issues

• Library changes affect all pipelines that use them.
• Groovy syntax errors in libraries are hard to debug.
• Version mismatches cause unexpected behavior.