YAML for GitHub Actions

A Quick and Simple Guide for Beginners

YAML (Yet Another Markup Language) is a clean, human-readable format used extensively in DevOps and infrastructure tools - and it's what we use to define workflows in GitHub Actions. If you're new to YAML, here's a quick introduction to help you understand the essentials before diving into workflows.

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✅ What is YAML?

• YAML is a way to organize data using key-value pairs. It is similar to how dictionaries work in Python or objects in JavaScript.

• It is indentation-sensitive and uses spaces, not tabs.

• YAML is used to create configuration files that are easy to read and organize.

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🔤 Primitive Data Types in YAML

YAML supports three basic primitive types:

• Strings

  • Can be unquoted: name: John

  • Or quoted (useful for special characters): name: "John Doe"

• Numbers

  • Example: age: 30

• Booleans

  • true or false

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🧱 Dictionaries (Nested Key-Value Pairs)

You can define nested dictionaries by indenting child keys:

config:
  path: "dir/file.yaml"
  environment: "staging"

This is commonly used in GitHub Actions under keys like jobs, steps, etc.

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📚 Arrays (Lists)

YAML uses a dash - to define list items:

env:  
  - development
  - staging
  - production

Lists can also contain complex objects:

env:  
  - name: development
    enable: phpmyadmin
  - name: staging
    enable: ['phpmyadmin', 'logzio']
  - name: production
    enable: 'logzio'

You can even nest arrays within arrays or objects:

env:
  - name: development
    enable:
      - phpmyadmin
      - lints
      - tests:
          depends-on: phpunit

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🧠 Indentation Rules

YAML relies on indentation to define structure:

• Always use consistent spaces (typically 2).

• Misaligned indentation results in invalid YAML.

Valid:

name: My Workflow
environment: staging

Invalid:

name: My Workflow
  environment: staging   # ❌ Wrong indentation

Hierarchical Example:

config:
  environment: staging

This implies: config.environment = staging

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💡 Final Tips

• Choose 2 or 4 spaces and stick to it throughout the file.

• Quoting strings is optional, but necessary when the value includes special characters or starts with a number.

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✍️ Why YAML Matters for GitHub Actions

YAML is the language GitHub Actions uses to:

• Define triggers (on: push)

• Configure jobs and steps

• Set environments, secrets, and conditionals

Understanding YAML helps you avoid syntax errors and build powerful automation workflows efficiently.