Guide to Yaml
Published: 2022-12-11 14:50:45

YAML (YAML Ain't Markup Language) is a human-readable data serialization language. It is often used for configuration files, but can be used in many other contexts as well. In this blog, we will take a look at the basics of YAML and how it can be used by developers.

First, let's define what a YAML file is. A YAML file is a text file that uses the YAML syntax to specify data structures. These data structures can be a mix of scalar values (strings, numbers, etc.), lists, and associative arrays (also known as maps or dictionaries).

Here is an example of a YAML file that defines a simple list:

```yml
- item1
- item2
- item3
```

This YAML file defines a list of three items: item1, item2, and item3. You can see that the list is denoted by a dash (-) followed by the item.

Now, let's take a look at how we can define a more complex data structure in YAML. Here is an example of a YAML file that defines an associative array:

```yaml
key1: value1
key2: value2
key3:
  - subkey1: subvalue1
  - subkey2: subvalue2

```

In this example, we have defined an associative array with three keys: key1, key2, and key3. The value for key1 and key2 are simple scalar values, but the value for key3 is a list of associative arrays.

One of the benefits of using YAML is that it is very readable and easy to write. It also supports comments, which can be useful for documenting your YAML files. Here is an example of a YAML file with comments:

```yaml
# This is a comment
key: value

# This is another comment
# It can span multiple lines
key2:
  - subkey1: subvalue1
  - subkey2: subvalue2

```
As you can see, comments in YAML are denoted by the # character and can be placed on their own line or after a value.

Another benefit of YAML is that it is versatile and can be used in many different contexts. For example, it is commonly used for configuration files in software projects. Here is an example of a YAML configuration file:

```yaml
# This is a sample configuration file

# Global settings
global:
  # The name of the project
  name: My Project

# Database settings
database:
  # The type of database to use
  type: mysql
  # The database host
  host: localhost
  # The database port
  port: 3306
  # The database username
  username: root
  # The database password
  password: password
 
```

In this example, we have defined a configuration file with two sections: global and database. The global section contains a single key-value pair, while the database section contains several keys with their corresponding values.

YAML is also used in other contexts, such as for defining Kubernetes resources. Here is an example of a YAML file that defines a Kubernetes Deployment:

```yml
apiVersion: apps/v
```

As mentioned earlier, YAML is a versatile language and can be used in many different contexts. In addition to configuration files and Kubernetes resources, YAML is also used in other tools and frameworks, such as Ansible and Rails.

In Ansible, YAML is used to define playbooks, which are files that specify a set of tasks to be executed on one or more remote hosts. Here is an example of an Ansible playbook written in YAML:

```yml
---
- hosts: all
  tasks:
    - name: Install Apache
      apt: name=apache2 state=present
    - name: Start Apache
      service: name=apache2 state=started

```

In this example, we have defined a playbook that installs and starts Apache on all hosts in the all group. The playbook is written in YAML and consists of two tasks: Install Apache and Start Apache.

In Rails, YAML is used for a variety of purposes, such as defining translations and fixtures. Here is an example of a YAML file used for defining translations in Rails:


```yml
en:
  hello: "Hello"
  world: "World"

fr:
  hello: "Bonjour"
  world: "Monde"

```
In this example, we have defined translations for the words "hello" and "world" in English and French. The translations are organized in a YAML file, with the language code as the key and the translations as the values.

As you can see, YAML is a useful and versatile language that can be used in many different contexts by developers. It is easy to read and write, supports comments, and can be used for a variety of purposes.


In conclusion, YAML is a human-readable data serialization language that is often used for configuration files and other purposes. It is easy to read and write, supports comments, and can be used in many different contexts, such as Ansible playbooks and Rails translations. Developers can use YAML to organize and represent their data in a clear and concise way.