Git Notes

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Introduction to GitHub Actions

GitHub Actions is a powerful automation platform built directly into GitHub that lets you create custom workflows triggered by events in your repository....

GitHub Actions is a powerful automation platform built directly into GitHub that lets you create custom workflows triggered by events in your repository. Whether you want to run tests on every push, deploy code when a release is published, or automate repetitive tasks like labeling issues, GitHub Actions handles it all without requiring external CI/CD services.

What Are GitHub Actions

At its core, GitHub Actions is an event-driven automation system. When something happens in your repository (a push, a pull request, a new issue, a scheduled time), GitHub Actions can execute a series of commands in response. These automated processes are called workflows.

Think of it as hiring a robot assistant that watches your repository 24/7 and performs tasks whenever specific events occur — running tests, building applications, sending notifications, or deploying to servers.

Core Concepts

Workflows

A workflow is an automated process defined in a YAML file. It lives in .github/workflows/ in your repository. A repository can have multiple workflows, each handling different automation needs.

Events

Events are triggers that start a workflow. Common events include:

push — Code is pushed to a branch
pull_request — A PR is opened, updated, or merged
schedule — Run at specific times (cron syntax)
release — A release is published
issues — An issue is created or modified
workflow_dispatch — Manually triggered from the UI

Jobs

A workflow contains one or more jobs. Each job runs on a virtual machine (runner) and contains a series of steps. Jobs run in parallel by default but can be configured to run sequentially.

Steps

Steps are individual tasks within a job. Each step is either a shell command or a reusable action.

Actions

Actions are reusable units of code that perform common tasks. The GitHub marketplace has thousands of community-created actions for everything from setting up programming languages to deploying applications.

Your First Workflow

Create .github/workflows/hello.yml:

Example

name: Hello World on: push: branches: [main] jobs: greet: runs-on: ubuntu-latest steps: - name: Print greeting run: echo "Hello from GitHub Actions!" - name: Print event information run: | echo "Event: ${{ github.event_name }}" echo "Branch: ${{ github.ref }}" echo "Actor: ${{ github.actor }}"

Push this file, and GitHub Actions immediately runs the workflow. Check the "Actions" tab in your repository to see the output.

A Practical CI Workflow

Here is a realistic workflow for a JavaScript project:

Example

name: CI on: push: branches: [main, develop] pull_request: branches: [main] jobs: build-and-test: runs-on: ubuntu-latest steps: - name: Checkout code uses: actions/checkout@v4 - name: Setup Node.js uses: actions/setup-node@v4 with: node-version: '20' cache: 'npm' - name: Install dependencies run: npm ci - name: Run linter run: npm run lint - name: Run tests run: npm test - name: Build application run: npm run build

Understanding Workflow Syntax

Triggers (on)

Example

on: # Push to specific branches push: branches: [main, 'release/**'] paths: ['src/**', 'package.json'] # Only trigger if these files change # Pull requests pull_request: types: [opened, synchronize, reopened] # Scheduled (cron) schedule: - cron: '0 9 * * MON' # Every Monday at 9 AM UTC # Manual trigger workflow_dispatch: inputs: environment: description: 'Deployment target' required: true default: 'staging'

Runners

yaml example

jobs:
  linux-job:
    runs-on: ubuntu-latest
  windows-job:
    runs-on: windows-latest
  mac-job:
    runs-on: macos-latest

Using Actions from Marketplace

yaml example

steps:
  - uses: actions/checkout@v4          # Official checkout action
  - uses: actions/setup-python@v5      # Set up Python
  - uses: actions/cache@v4             # Cache dependencies
  - uses: peaceiris/actions-gh-pages@v4  # Community action for GitHub Pages

Environment Variables and Secrets

yaml example

env:
  NODE_ENV: production

jobs:
  deploy:
    env:
      API_URL: https://api.example.com
    steps:
      - name: Deploy
        env:
          SECRET_KEY: ${{ secrets.SECRET_KEY }}
        run: deploy.sh

Conditional Execution

Run steps or jobs only when certain conditions are met:

yaml example

steps:
  - name: Deploy to production
    if: github.ref == 'refs/heads/main'
    run: npm run deploy:prod
    
  - name: Deploy to staging
    if: github.ref == 'refs/heads/develop'
    run: npm run deploy:staging
    
  - name: Notify on failure
    if: failure()
    run: echo "Something went wrong!"

Job Dependencies

Control the order of job execution:

Example

jobs: test: runs-on: ubuntu-latest steps: - run: npm test build: needs: test # Runs after test passes runs-on: ubuntu-latest steps: - run: npm run build deploy: needs: [test, build] # Runs after both complete runs-on: ubuntu-latest steps: - run: npm run deploy

Viewing Workflow Results

After a workflow runs:

Go to the "Actions" tab in your repository
Click on the workflow run to see job details
Expand each step to see its output
Check status badges in PRs for pass/fail indication

Key Takeaways

GitHub Actions brings automation directly into your development workflow. Workflows are event-driven YAML files that define jobs and steps. Actions from the marketplace handle common tasks, while shell commands cover custom logic. Start with a simple test workflow and expand as your automation needs grow. The platform scales from individual projects to enterprise organizations, making it the natural choice for CI/CD when your code already lives on GitHub.

Exam Focus

Revise definitions, diagrams, examples, and short-answer points for Introduction to GitHub Actions.

Interview Use

Prepare one clear explanation, one practical example, and one common mistake for this Git & GitHub topic.

Search Terms

git-github, git & github, git, github, actions, introduction, introduction to github actions

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Git Notes

Introduction to GitHub Actions

GitHub Actions is a powerful automation platform built directly into GitHub that lets you create custom workflows triggered by events in your repository....

What Are GitHub Actions

Core Concepts

Workflows

A workflow is an automated process defined in a YAML file. It lives in .github/workflows/ in your repository. A repository can have multiple workflows, each handling different automation needs.

Events

Events are triggers that start a workflow. Common events include:

push — Code is pushed to a branch
pull_request — A PR is opened, updated, or merged
schedule — Run at specific times (cron syntax)
release — A release is published
issues — An issue is created or modified
workflow_dispatch — Manually triggered from the UI

Jobs

A workflow contains one or more jobs. Each job runs on a virtual machine (runner) and contains a series of steps. Jobs run in parallel by default but can be configured to run sequentially.

Steps

Steps are individual tasks within a job. Each step is either a shell command or a reusable action.

Actions

Your First Workflow

Create .github/workflows/hello.yml:

Example

Push this file, and GitHub Actions immediately runs the workflow. Check the "Actions" tab in your repository to see the output.

A Practical CI Workflow

Here is a realistic workflow for a JavaScript project:

Example

Understanding Workflow Syntax

Triggers (on)

Example

Runners

yaml example

jobs:
  linux-job:
    runs-on: ubuntu-latest
  windows-job:
    runs-on: windows-latest
  mac-job:
    runs-on: macos-latest

Using Actions from Marketplace

yaml example

steps:
  - uses: actions/checkout@v4          # Official checkout action
  - uses: actions/setup-python@v5      # Set up Python
  - uses: actions/cache@v4             # Cache dependencies
  - uses: peaceiris/actions-gh-pages@v4  # Community action for GitHub Pages

Environment Variables and Secrets

yaml example

env:
  NODE_ENV: production

jobs:
  deploy:
    env:
      API_URL: https://api.example.com
    steps:
      - name: Deploy
        env:
          SECRET_KEY: ${{ secrets.SECRET_KEY }}
        run: deploy.sh

Conditional Execution

Run steps or jobs only when certain conditions are met:

yaml example

steps:
  - name: Deploy to production
    if: github.ref == 'refs/heads/main'
    run: npm run deploy:prod
    
  - name: Deploy to staging
    if: github.ref == 'refs/heads/develop'
    run: npm run deploy:staging
    
  - name: Notify on failure
    if: failure()
    run: echo "Something went wrong!"

Job Dependencies

Control the order of job execution:

Example

Viewing Workflow Results

After a workflow runs:

Go to the "Actions" tab in your repository
Click on the workflow run to see job details
Expand each step to see its output
Check status badges in PRs for pass/fail indication

Key Takeaways

Exam Focus

Revise definitions, diagrams, examples, and short-answer points for Introduction to GitHub Actions.

Interview Use

Prepare one clear explanation, one practical example, and one common mistake for this Git & GitHub topic.

Search Terms

git-github, git & github, git, github, actions, introduction, introduction to github actions

Related Git & GitHub Topics

Continue learning this concept

PreviousDeployment Automation with GitHub Actions NextGitHub Actions Runners