How to Use Script Block in Declarative Jenkins Pipeline

In Jenkins declarative pipelines, use the script block to run Groovy code that is not supported directly by declarative syntax. Place the script block inside a steps section to execute complex logic or custom scripts.

Syntax

The script block allows you to run Groovy code inside a declarative pipeline. It must be placed inside a steps block. This lets you use imperative Groovy code where declarative syntax is limited.

• pipeline: The root block for declarative pipelines.
• stage: Defines a stage in the pipeline.
• steps: Contains the commands or scripts to run.
• script: Runs Groovy code inside declarative syntax.

groovy

pipeline {
  agent any
  stages {
    stage('Example') {
      steps {
        script {
          // Groovy code here
          echo "Hello from script block"
        }
      }
    }
  }
}

Example

This example shows how to use the script block to run Groovy code that prints a message and uses a loop, which is not possible directly in declarative syntax.

groovy

pipeline {
  agent any
  stages {
    stage('Script Block Demo') {
      steps {
        script {
          echo 'Starting loop in script block'
          for (int i = 1; i <= 3; i++) {
            echo "Loop iteration: ${i}"
          }
          echo 'Loop finished'
        }
      }
    }
  }
}

Output

[Pipeline] echo
Starting loop in script block
[Pipeline] echo
Loop iteration: 1
[Pipeline] echo
Loop iteration: 2
[Pipeline] echo
Loop iteration: 3
[Pipeline] echo
Loop finished

Common Pitfalls

Common mistakes when using the script block include:

• Placing script outside steps causes syntax errors.
• Using declarative-only steps inside script block without proper Groovy syntax.
• Not handling exceptions inside script block can cause pipeline failures.

Always remember script is for Groovy code, so use Groovy syntax inside it.

groovy

pipeline {
  agent any
  stages {
    stage('Wrong Usage') {
      // This will cause error because script is outside steps
      script {
        echo 'This is wrong placement'
      }
    }
  }
}

// Correct usage:
pipeline {
  agent any
  stages {
    stage('Right Usage') {
      steps {
        script {
          echo 'This is correct placement'
        }
      }
    }
  }
}

Quick Reference

Use the script block inside steps to run Groovy code in declarative pipelines. It enables complex logic like loops, conditionals, and variable manipulation not possible in pure declarative syntax.

• Always place script inside steps.
• Use Groovy syntax inside script.
• Keep declarative and scripted parts clear for readability.

Key Takeaways

Use the script block inside steps to run Groovy code in declarative pipelines.

Place script only inside steps to avoid syntax errors.

The script block allows loops, conditionals, and complex logic not supported by declarative syntax.

Write Groovy code inside script using proper Groovy syntax.

Keep your pipeline readable by separating declarative and scripted parts clearly.