YAML stands for “YAML Ain’t Markup Language.” It is a human-readable data serialization language used for configuration files and data exchange between languages with different data structures. YAML is often used in programming environments, particularly for configuration files in software applications, and for data exchange in web services.
YAML is designed to be easily readable by humans and can be used to represent data structures like lists, arrays, and associative arrays (also known as maps or dictionaries). It is commonly used in configuration files for software applications, infrastructure automation, and data exchange between different programming languages.
Syntax
YAML uses indentation to represent hierarchy and structure, similar to how Python uses indentation. This makes it visually clear and easy to understand the structure of the data. Here are some key aspects of YAML syntax:
- Scalars: These are simple values like strings, integers, and floats. In YAML, scalars can be written without quotes, but quotes can be used to ensure that a value is interpreted as a string.
-
Lists: Represented as a sequence of items, each item in a list is preceded by a dash (
-) and a space. -
Maps: Also known as associative arrays or dictionaries, maps are represented as a collection of key-value pairs. Each pair is separated by a colon (
:) and a space. -
Comments: YAML supports comments, which are preceded by a hash symbol (
#). Comments are ignored by the parser.
Example: This is a simple example of a YAML file.
# Sample YAML file name: John Doe age: 30 married: true children: - name: Jane Doe
age: 10
- name: Jack Doe
age: 8
languages: - English
- French
|
In this example, we have a map with keys name, age, married, children, and languages. The children key contains a list of maps, each representing a child. The languages key contains a list of strings.
Usage of YAML
YAML is used for a variety of purposes, primarily in software development and configuration management. Some common uses of YAML include:
- Configuration Files: YAML is often used to write configuration files for software applications, servers, and development tools. Its human-readable format makes it easy to create and maintain configurations for complex systems.
- Data Serialization and Deserialization: YAML can be used to serialize and deserialize data structures, making it useful for data exchange between different programming languages or systems.
- Infrastructure as Code (IaC): In the context of cloud computing and DevOps, YAML is used to define infrastructure resources in a readable and versionable format. Tools like AWS CloudFormation, Kubernetes, and Terraform use YAML to specify the desired state of infrastructure resources.
- Continuous Integration and Continuous Deployment (CI/CD): YAML is commonly used to define workflows and pipelines in CI/CD systems, such as GitHub Actions, GitLab CI/CD, and Jenkins.
- Docker Compose: In the world of containerization, YAML is used to define multi-container Docker applications using Docker Compose files.
- API Definitions: YAML is often used to write OpenAPI (formerly Swagger) specifications for RESTful APIs, providing a clear and structured way to describe API endpoints, parameters, and responses.
- Data Storage: Although not as common as other formats like JSON or XML, YAML can be used to store data in a human-readable format.
Overall, YAML is valued for its simplicity, readability, and flexibility, making it a popular choice for a wide range of applications in software development and infrastructure management.