Alt text for the image I always wondered what YAML files were. As a programmer, I’ve seen them frequently, and after some research, I finally understand them. Programmers don’t usually write YAML directly, but it’s incredibly useful to know how they work so you can understand your configuration files.




What is YAML?

  • Human-friendly Data: YAML (originally Yet Another Markup Language, but now stands for YAML Ain’t Markup Language) is designed to be a data serialization language that’s exceptionally easy for humans to read and write.
  • Configuration Files and More: It’s frequently used for configuration files, but its capabilities go beyond that. YAML can represent complex data structures, making it suitable for various data-related tasks.

Key Features

  • Readability: YAML’s core strength is its readability. It emphasizes a clean syntax that avoids excessive punctuation and symbols.
  • Indentation-Based Structure: Unlike JSON or XML, YAML uses indentation (SPACE, NOT TABS) to define the structure of data. This makes it visually intuitive.
  • Superset of JSON: If you know JSON, you already understand a good chunk of YAML.
  • Data Types: YAML supports common data types:
    • Scalars (strings, numbers, booleans)
    • Lists (sequences, similar to arrays)
    • Dictionaries (key-value pairs, also called maps or hashes)

Note: .yml and .yaml mean the same thing. Comments are made using #.

Example

Here’s a simple example of a YAML configuration file that demonstrates common YAML features:

person:
  name: "Mike"
  occupation: 'Programmer'
  age: 23
  fav_num: 1e+10 # Exponential number
  male: true # Boolean value
  birthday: 2001-12-25 # ISO 8601 date format

  hobbies:
    - Hiking
    - Movies

  movie: 
    - "Source Code"
    - "" # An empty element in the list

  friends:
    - name: "Steph"
      age: 22

# Description and signature with specific formatting directives
description: > # Treats everything within as a single line 
  This is a single-line text despite the breaks, demonstrating YAML's flexibility in handling text blocks.
signature: | # Preserves the formatting 
  Gmail
  Name
  School

# Advanced structures with anchors and aliases
person_alias: &person
  name: "Mike"
  occupation: "Programmer"
friends_list:
  - <<: *person
    age: 22
    relationship: "Colleague"

# Data type enforcement
age: !!float 23 # Interpreted as 23.0
gpa: !!str 3.5 # Interpreted as a string "3.5"

Example from My Blog, you see this _config.yml in my repo:

title: Rand Tech Blog
description: >-  
  I document things.
baseurl: "" 
url: "https://github.com/kaden175ck/kaden175ck.github.io.git" 
github_username: kaden175ck

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