The leading open source automation server, Jenkins provides hundreds of plugins to support building, deploying and automating any project.

Jenkins exposes characteristics of components using Environment variables. This blog will tell you everything about Environment variables.

1. Creating Global environment variables
2. Access Global environment variables.
3. Creating local environment variables during build.

1. Creating global environment variables:

1.1 Using Jenkins Console

we can easily create global environment variables.

Manage Jenkins => Configure

Under section Global Properties, check Environment variables checkbox. Now Jenkins allow us to add key and value pairs which will be accessible with in each node and each build.

1.2 Using Groovy/Java

To create global environment variable, we need to use below code.

import hudson.EnvVars;
import hudson.slaves.EnvironmentVariablesNodeProperty;
import hudson.slaves.NodeProperty;
import hudson.slaves.NodePropertyDescriptor;
import hudson.util.DescribableList;
import jenkins.model.Jenkins;public createGlobalEnvironmentVariables(String key, String value){

Jenkins instance = Jenkins.getInstance();

DescribableList<NodeProperty<?>, NodePropertyDescriptor> globalNodeProperties = instance.getGlobalNodeProperties();
List<EnvironmentVariablesNodeProperty> envVarsNodePropertyList = globalNodeProperties.getAll(EnvironmentVariablesNodeProperty.class);

EnvironmentVariablesNodeProperty newEnvVarsNodeProperty = null;
EnvVars envVars = null;

if ( envVarsNodePropertyList == null || envVarsNodePropertyList.size() == 0 ) {
            newEnvVarsNodeProperty = new hudson.slaves.EnvironmentVariablesNodeProperty();
            globalNodeProperties.add(newEnvVarsNodeProperty);
            envVars = newEnvVarsNodeProperty.getEnvVars();
        } else {
            envVars = envVarsNodePropertyList.get(0).getEnvVars();
        }
        envVars.put(key, value)
        instance.save()
}createGlobalEnvironmentVariables('Var1','DummyValue')

2. Access Global Environment variables

2.1 In jenkins Pipeline

To use above defined variable in pipeline we can use env.Key give us access to out jenkins global variables.

pipeline {
    agent any
    stages {
        stage('Build') {
            steps {
                echo env.Var1
            }
        }
    }
}

In jenkins pipeline there are lot of other useful environment variables which can be accessed during build execution.

Most useful environment variables. Highly recommended to check out.

1. env: Environment variables are accessible from Groovy code as env.VARNAME or simply as VARNAME. You can write to such properties as well (only using the env. prefix):
2. currentBuild: The currentBuild variable may be used to refer to the currently running build.
3. params: Exposes all parameters defined in the build as a read-only map with variously typed values.
4. docker : The docker variable offers convenient access to Docker-related functions from a Pipeline script.

In pipeline job -> pipeline Syntax -> Global Variable Reference

2.2 In Shell/Batch Script

In Shell script we can use environment variables using $Key or ${Key}. Similarly in batch we can use %Key% to access Environment Variables.

2.3 In FreeStyle projects

In freestyle project we can use EnvEnject Plugin.

3. Creating local environment variables during build.

3.1 Using Declarative pipeline

Jenkinsfile (Declarative Pipeline)

pipeline {
    agent any
    environment {
        DISABLE_AUTH = 'true'
    }
    stages {
        stage('Build') {
            steps {
                echo env.DISABLE_AUTH
            }
        }
    }
}

3.2 Using Scripted pipeline.

node{
    stage('Build') {
        withEnv(["DISABLE_AUTH=true"]) {
          echo env.DISABLE_AUTH
       }
    }
}