Environment variables access in Jenkins - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an environment variable in Jenkins?

An environment variable in Jenkins is a key-value pair that stores information accessible to Jenkins jobs during their execution. It helps configure jobs without hardcoding values.

beginner

How do you access an environment variable in a Jenkins Pipeline script?

You access an environment variable in a Jenkins Pipeline using the syntax: env.VARIABLE_NAME. For example, env.BUILD_NUMBER gives the current build number.

intermediate

How can you set a custom environment variable in a Jenkins Pipeline?

You can set a custom environment variable inside the environment block in a Jenkins Pipeline like this:

environment {
  MY_VAR = 'Hello'
}

intermediate

What is the difference between global and job-specific environment variables in Jenkins?

Global environment variables are set for all Jenkins jobs and agents, while job-specific variables are defined only within a particular job or pipeline.

intermediate

How do you print all environment variables in a Jenkins Pipeline?

You can print all environment variables using a shell step:

sh 'printenv'

or in a scripted pipeline:

env.each { k, v -> println "${k} = ${v}" }

How do you access the environment variable named 'PATH' in a Jenkins Pipeline script?

A getEnv('PATH')

B PATH.env

C env.PATH

D environment.PATH

In Jenkins Pipeline, environment variables are accessed using the 'env' object followed by the variable name, like env.PATH.

Where do you define custom environment variables for a Jenkins Pipeline?

A Inside the environment block

B In the Jenkins global config only

C Inside the steps block

D In the Jenkinsfile header comment

Custom environment variables are defined inside the 'environment' block in a Jenkins Pipeline.

Which command prints all environment variables in a Jenkins Pipeline shell step?

A listenv

B printenv

C showenv

D envlist

The 'printenv' command lists all environment variables in a shell environment.

What is the scope of environment variables defined in the Jenkins global configuration?

A Only available during build steps

B Only available to one job

C Only available in post-build actions

D Available to all jobs and agents

Global environment variables are accessible to all Jenkins jobs and agents.

How do you access the current build number in a Jenkins Pipeline?

A env.BUILD_NUMBER

B build.number

C currentBuild.number

D env.BUILDNUM

The current build number is available as the environment variable 'BUILD_NUMBER', accessed via env.BUILD_NUMBER.

Explain how to set and access environment variables in a Jenkins Pipeline.

Think about the environment block and the env object.

Describe the difference between global and job-specific environment variables in Jenkins.

Consider scope and configuration location.

Practice

1. In a Jenkins Pipeline script, how do you access an environment variable named BUILD_NUMBER?

easy

A. Using BUILD_NUMBER directly without prefix

B. Using env.BUILD_NUMBER

C. Using getEnv('BUILD_NUMBER')

D. Using $BUILD_NUMBER inside the script block

Solution

1. Step 1: Understand Jenkins environment variable access

   Jenkins Pipeline exposes environment variables via the env object.

2. Step 2: Access the variable using the correct syntax

   You access BUILD_NUMBER as env.BUILD_NUMBER in the script.

3. Final Answer:

   Using env.BUILD_NUMBER -> Option B

4. Quick Check:

   env.VARIABLE_NAME = correct access [OK]

Hint: Always prefix environment variables with env. in Jenkins [OK]

Common Mistakes:

• Trying to use variable name without env prefix
• Using shell-style $VARIABLE inside Groovy script
• Calling non-existent getEnv() method

2. Which of the following is the correct syntax to print the environment variable JOB_NAME in a Jenkins Pipeline script block?

easy

A. println("JOB_NAME")

B. echo $JOB_NAME

C. println(env.JOB_NAME)

D. print(JOB_NAME)

Solution

1. Step 1: Identify the correct way to print env variables in Groovy script

   In Jenkins Pipeline Groovy scripts, use println(env.VARIABLE) to print environment variables.

2. Step 2: Check each option

   println("JOB_NAME") prints the string "JOB_NAME" literally. echo $JOB_NAME uses shell syntax, invalid in Groovy. print(JOB_NAME) attempts to print JOB_NAME directly, but it's not available in Groovy scope without env prefix.

3. Final Answer:

   println(env.JOB_NAME) -> Option C

4. Quick Check:

   Use println(env.VARIABLE) to print env vars in script [OK]

Hint: Use println(env.VARIABLE) inside script blocks [OK]

Common Mistakes:

• Using shell syntax like $VARIABLE inside Groovy
• Printing variable name as string instead of value
• Trying to access variables without env. prefix

3. Given this Jenkins Pipeline snippet:

pipeline {
  agent any
  stages {
    stage('Print Env') {
      steps {
        script {
          echo "Branch is: ${env.BRANCH_NAME}"
        }
      }
    }
  }
}

What will be the output if the environment variable BRANCH_NAME is set to feature-123?

medium

A. Branch is: feature-123

B. Branch is: ${env.BRANCH_NAME}

C. Branch is: BRANCH_NAME

D. Error: BRANCH_NAME not found

Solution

1. Step 1: Understand string interpolation in Jenkins Pipeline

   Using double quotes with ${env.BRANCH_NAME} interpolates the variable value.

2. Step 2: Substitute the environment variable value

   Since BRANCH_NAME is set to "feature-123", the output will be "Branch is: feature-123".

3. Final Answer:

   Branch is: feature-123 -> Option A

4. Quick Check:

   Double quotes + ${env.VAR} = variable value [OK]

Hint: Use double quotes and ${env.VAR} for variable interpolation [OK]

Common Mistakes:

• Using single quotes which prevent interpolation
• Printing variable name literally without ${}
• Assuming env variables are undefined

4. You wrote this Jenkins Pipeline snippet:

pipeline {
  agent any
  environment {
    MY_VAR = 'hello'
  }
  stages {
    stage('Test') {
      steps {
        script {
          echo env.MY_VAR
        }
      }
    }
  }
}

But the output is empty. What is the likely cause?

medium

A. The environment block syntax is incorrect; use MY_VAR='hello' with quotes and no spaces around =

B. Environment variables must be accessed as env['MY_VAR'] not env.MY_VAR

C. The environment variable was not set correctly; use MY_VAR='hello' without spaces

D. You cannot access environment variables inside script blocks

Solution

1. Step 1: Check environment block syntax

   In Jenkins Pipeline, environment variables must be assigned with no spaces around = and values in quotes, like MY_VAR='hello'.

2. Step 2: Identify the syntax error in the snippet

   The snippet uses MY_VAR = 'hello' with spaces around = which is invalid and causes the variable not to be set.

3. Final Answer:

   The environment block syntax is incorrect; use MY_VAR='hello' with quotes and no spaces around = -> Option A

4. Quick Check:

   Use no spaces around = in environment block [OK]

Hint: No spaces around = in environment block assignments [OK]

Common Mistakes:

• Adding spaces around = in environment variable assignment
• Trying to access env vars incorrectly
• Assuming script block can't access env vars

5. You want to pass a secret API key stored as an environment variable API_KEY to a shell command in Jenkins Pipeline. Which is the best way to do this securely?

hard

A. Use sh "curl -H 'Authorization: Bearer $API_KEY' https://api.example.com"

B. Use sh(script: "curl -H 'Authorization: Bearer ${env.API_KEY}' https://api.example.com")

C. Use sh(script: "curl -H 'Authorization: Bearer $API_KEY' https://api.example.com", environment: [API_KEY: env.API_KEY])

D. Use Jenkins credentials binding plugin to inject API_KEY and access it as env.API_KEY inside sh

Solution

1. Step 1: Understand secure handling of secrets in Jenkins

   Secrets like API keys should be stored in Jenkins credentials and injected securely, not hardcoded or exposed in logs.

2. Step 2: Use credentials binding plugin

   This plugin injects secrets as environment variables during the build, accessible as env.API_KEY inside sh without exposing them in logs.

3. Final Answer:

   Use Jenkins credentials binding plugin to inject API_KEY and access it as env.API_KEY inside sh -> Option D

4. Quick Check:

   Use credentials plugin for secrets, not plain env vars [OK]

Hint: Use Jenkins credentials plugin for secrets, not plain env vars [OK]

Common Mistakes:

• Passing secrets directly in shell commands risking exposure
• Using string interpolation exposing secrets in logs
• Not using Jenkins credentials plugin for sensitive data