Lab: List Environment Variables

Introduction

In this lab, you will learn how to display environment variables in Linux, macOS, and Windows operating systems using GitHub Actions.

GitHub Actions allows you to display environment variables in the logs. This can be useful for debugging purposes or to understand the environment in which your code is running. Please note that these environment variables are not secure and should not be used to store sensitive information. Additionally, they are case-sensitive.

Estimated Duration: 20-30 minutes

Instructions

Step 1: Create a YAML Workflow File

  1. In your repository, create a directory .github/workflows if it doesn’t exist.

  2. Inside .github/workflows, create a new file named env-var-list.yml.

  3. Add the following content to env-var-list.yml:

    name: Env Var List

on:
  workflow_dispatch:
  push:
    paths:
      - '.github/workflows/env-var-list.yml'

jobs:
  ubuntu:
    runs-on: ubuntu-latest
    steps:
      - name: Display Environment Variables on Ubuntu
        run: printenv | sort

  mac:
    runs-on: macos-latest
    steps:
      - name: Display Environment Variables on MacOS
        run: printenv | sort

  windows:
    runs-on: windows-latest
    steps:
      - name: Display Environment Variables on Windows
        run: printenv | sort
        shell: bash

  4. Commit the file to the main branch.

Step 2: Understanding the Workflow

  1. Name: The workflow is named Env Var List.

  2. Triggers (on):

    • workflow_dispatch enables manual triggering from GitHub Actions tab.
    • push triggers when env-var-list.yml changes.

  3. Jobs:

    • ubuntu runs on ubuntu-latest.
    • mac runs on macos-latest.
    • windows runs on windows-latest.
  4. Steps: Each job runs printenv | sort to display environment variables in alphabetical order.

Step 3: Commit and Trigger the Workflow

  1. After committing, go to the Actions tab in your GitHub repository.
  2. Select the Env Var List workflow.
  3. Click the Run workflow button.
  4. Choose the main branch and click Run workflow to start.

Step 4: View Workflow Results

  1. Once the workflow completes, open the run details.
  2. Click on each job (ubuntu, mac, windows) to view their logs.
  3. Expand the step named Display Environment Variables to see the output for each operating system.

Step 5: (Optional) Use a Matrix Strategy for Parallel Execution

You can simplify the workflow using a matrix to run jobs in parallel on all three OSes:

jobs:
  display-environment-variables:
    strategy:
      matrix:
        os: [ubuntu-latest, macos-latest, windows-latest]
    runs-on: $
    steps:
      - name: Display Environment Variables
        run: printenv | sort
        shell: bash
  1. Replace the jobs section with the above.
  2. Commit and rerun the workflow.

Summary

You created a workflow file from scratch, configured jobs on Ubuntu, macOS, and Windows runners, displayed environment variables, triggered workflows manually and on push, and optionally used a matrix strategy for cleaner parallel execution.

Additional Resources