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Writing Reusable Steps with vars/

The vars/ directory is used to define global, reusable pipeline steps. These steps are callable directly from a Jenkinsfile and are the most common entry point for shared libraries.

What Goes into vars/​

Use vars/ for:

  • High-level pipeline steps
  • Reusable stages or stage groups
  • Thin orchestration logic

Avoid:

  • Heavy business logic
  • Complex class hierarchies

Naming Rules​

  • Filename = step name
  • Must be a valid Groovy identifier
  • Case-sensitive

Example:

vars/
└── buildAndTest.groovy

Callable as:

buildAndTest()

Mandatory call() Method​

Each vars file must implement a call() method.

def call() {
  stage('Build') {
    sh 'mvn clean package'
  }
}

Without call(), Jenkins cannot invoke the step.

Accepting Parameters​

Reusable steps can accept parameters like normal Groovy methods.

def call(Map config = [:]) {
  def envName = config.get('env', 'qa')
  echo "Running for ${envName}"
}

Usage:

buildAndTest(env: 'prod')

Using Pipeline Steps Inside vars​

Pipeline steps (sh, echo, stage, etc.) are available automatically.

def call() {
  sh 'echo Running inside shared lib'
}

No imports required.

Accessing Environment Variables​

def call() {
  echo "Build number: ${env.BUILD_NUMBER}"
}

Use env safely for read-only access.

Error Handling​

def call() {
  try {
    sh 'run-tests.sh'
  } catch (e) {
    error "Tests failed"
  }
}

Use error() to fail the pipeline explicitly.

Common Mistakes​

  • Putting too much logic in vars
  • Forgetting call() method
  • Hardcoding environment values
  • Mixing credentials logic directly

Best Practices​

  • Keep vars steps small and readable
  • Delegate complex logic to src classes
  • Use Map-based parameters for flexibility
  • Version shared libraries

Interview Focus Areas​

  • Why call() is required
  • How vars steps are loaded
  • Difference between vars and src usage