Environment variables in builds in Jenkins - Mini Project: Build & Apply

Environment variables in builds

📖 Scenario: You are setting up a Jenkins pipeline to build a simple project. You want to use environment variables to store important values like the project name and build number. This helps keep your build script clean and easy to update.

🎯 Goal: Build a Jenkins pipeline script that defines environment variables and uses them in the build steps to print messages with those variables.

📋 What You'll Learn

Create environment variables in the Jenkins pipeline script

Use the environment variables inside the pipeline steps

Print the values of the environment variables during the build

💡 Why This Matters

🌍 Real World

Environment variables in Jenkins pipelines are used to store configuration values like project names, build numbers, and deployment targets. This makes builds flexible and easier to maintain.

💼 Career

Knowing how to use environment variables in Jenkins is essential for DevOps engineers and build managers to create reusable and configurable build pipelines.

1

Define environment variables in the pipeline

Create a Jenkins pipeline script with an environment block that defines two variables: PROJECT_NAME set to MyApp and BUILD_NUMBER set to 42.

Jenkins

pipeline {
    agent any
    environment {
        // Define PROJECT_NAME and BUILD_NUMBER here
    }
    stages {
        stage('Build') {
            steps {
                // Your code here
            }
        }
    }
}

Need a hint?

Use the environment block inside the pipeline to define variables.

2

Use environment variables in a build step

Inside the Build stage's steps, add a script block that assigns a variable called message with the value Building project: ${PROJECT_NAME} - Build number: ${BUILD_NUMBER}.

Jenkins

pipeline {
    agent any
    environment {
        PROJECT_NAME = 'MyApp'
        BUILD_NUMBER = '42'
    }
    stages {
        stage('Build') {
            steps {
                script {
                    // Assign message variable here
                }
            }
        }
    }
}

Need a hint?

Use def message = "Building project: ${PROJECT_NAME} - Build number: ${BUILD_NUMBER}" inside a script block.

3

Print the message variable

Still inside the script block, add a println(message) statement to print the message to the build log.

Jenkins

pipeline {
    agent any
    environment {
        PROJECT_NAME = 'MyApp'
        BUILD_NUMBER = '42'
    }
    stages {
        stage('Build') {
            steps {
                script {
                    def message = "Building project: ${PROJECT_NAME} - Build number: ${BUILD_NUMBER}"
                    // Print the message here
                }
            }
        }
    }
}

Need a hint?

Use println(message) to print the message inside the script block.

4

Run the pipeline and check output

Run the Jenkins pipeline script and verify that the build log shows the line: Building project: MyApp - Build number: 42.

Jenkins

pipeline {
    agent any
    environment {
        PROJECT_NAME = 'MyApp'
        BUILD_NUMBER = '42'
    }
    stages {
        stage('Build') {
            steps {
                script {
                    def message = "Building project: ${PROJECT_NAME} - Build number: ${BUILD_NUMBER}"
                    println(message)
                }
            }
        }
    }
}

// Run the pipeline and check the output in the Jenkins console log

Need a hint?

Look at the Jenkins build console output to see the printed message.