Ansible - Automation Essentials - Part 2 [ Introduction to YAML Language ]

What is YAML?

YAML stands for Yet Another Markup Language. It is a data serialization language just like JSON.

Why YAML, when we already have JSON or XML?

• YAML files are easy to read and write for humans, similar to English.

Foundation of YAML

• YAML files should end as .yaml or .yml
• Begins with --- and ends with …
• # defines comment

YAML is Case and Indentation Sensitive

• Members of a list should be at the same indentation level starting with a dash(-) and space.
• Each item in the list is a key: value pair (colon must be followed by a space), called a dictionary.
• At each level, exactly two spaces are used for indentation. Using tabs is not recommended here.

Boolean Values

Variables can be defined in YAML files as shown:

stream: Java

allocated: true

allocated: yes

allocated: no

allocated: True

allocated: TRUE

allocated: false

Variables can be assigned boolean values in different ways as shown:

Data Structures

Complicated data structures are possible in YAML.

You can define lists having dictionaries, dictionaries having lists or a mix of both.

In the following example,

• name and job are dictionaries. Skill is a dictionary with a list.
• David and Amy are listed as having dictionaries

# Employee records

-  David:

    name: David Moore

    job: Developer

    skills:

      - python

      - sql

      - java

-  Amy:

    name: Amy Brown

    job: Developer

    skills:

      - angular

      - redux

      - react