YAML CheatSheet

YAML is a data serialization language that is often used for writing configuration files.

YAML stands for yet another markup language or YAML aint markup language (a recursive acronym), which emphasizes that YAML is for data, not documents.

YAML is a popular programming language because it is human-readable and easy to understand. It can also be used in conjunction with other programming languages.

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• YAML does not allow the use of tabs
• Must be space between the element parts
• YAML is CASE sensitive
• End your YAML file with the .yaml or .yml extension
• YAML is a superset of JSON
• Ansible playbooks are YAML files

• In YAML, there is no extra delimiter is used. So it is the lightweight than XML and JSON.
• YAML, not using delimiter also makes the reading light and simple. (I am not sure if you agree with this point. Because many geeks find it easier to read the data in content delimiter or tags separate those.)
• YAML makes the data understanding easy. So it is useful in case of configuration.
• YAML has a wide variety of uses and popular for. It can be used for configuration, then from transferring data to storing intermediate data.
• YAML is the superset of JSON. You heard it right. Whatever valid JSON code you have, it will be parsed by YAML compiler. So choosing YAML over JSON for your project you have one advantage. You can parse both JSON and YAML code with the single parser (YAML parser).

• There are so many applications that are already build using XML or JSON, so it hard for a developer to replace this with YAML.
  For instance, I am developing a plugin for the existing project which uses XML. I would like to use XML in the plugin. So it will be easy for me to merge plugin with an existing project.
• Talking about the popularity, XML has much more matured ecosystem than YAML.
• JSON [JavaScript Object Notation] exists since early 2000s and it is highly adopted by many as compare to YAML. So it is easier to find the support for JSON over YAML.
• There are extra precautions while writing YAML code. Even if you mismatch single space while indentation, your code can stop working.
• There are many ways to represent data in YAML and make data hierarchy. So it is complex for processing. So JSON and XML have better performance than YAML.

n1: 2            # integer          
n2: 1.23444        # float      

s1: 'abcdf'        # string        
s2: "abcdf"        # string           
s3: abcdf          # string           

b: true         # boolean type 

d: 2016-04-07    # date type

---

Json Preview

{
  "n1": 2,
  "n2": 1.23444,
  "s1": "abcdf",
  "s2": "abcdf",
  "s3": "abcdf",
  "b": true,
  "d": "2016-04-07"
}

some_thing: &VAR_NAME foobar

other_thing: *VAR_NAME

---

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{
  "some_thing": "foobar",
  "other_thing": "foobar"
}

# A single line comment example

# block level comment example
# comment line 1
# comment line 2
# comment line 3

description: |
  hello
  bestforstudy.com

---

Json Preview

{"description": "hello\nbestforstudy.com\n"}

parent: &defaults
  a: 2
  b: 3

child:
  <<: *defaults
  b: 4

---

Json Preview

{
  "parent": {
    "a": 2,
    "b": 3
  },
  "child": {
    "a": 2,
    "b": 4
  }
}

values: &ref
  - Will be
  - reused below
  
other_values:
  i_am_ref: *ref

---

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{
  "values": [
    "Will be",
    "reused below"
  ],
  "other_values": {
    "i_am_ref": [
      "Will be",
      "reused below"
    ]
  }
}

description: >
  hello
  world

---

Json Preview

{"description": "hello world\n"}

---
document: this is doc 1
---
document: this is doc 2

- Jackson
- Jack
- Jess

---

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[
  "Jackson",
  "Jack",
  "Jess"
]

hr:  65       # Home runs
avg: 0.278    # Batting average
rbi: 147      # Runs Batted In

---

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{
  "hr": 65,
  "avg": 0.278,
  "rbi": 147
}

attributes:
  - b1
  - c2
methods: [getter, setter, void]

---

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{
  "attributes": ["b1", "c2"],
  "methods": ["getter", "setter", "void"]
}

children:
  - name: Jimmy Smith
    age: 15
  - name: Jimmy Smith
    age: 15
  -
    name: Sammy Sosa
    age: 12

---

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{
  "children": [
    {
      "name": "Jimmy Smith",
      "age": 15
    },
    {
      "name": "Jimmy Smith",
      "age": 15
    },
    {
      "name": "Sammy Sosa",
      "age": 12
    }
  ]
}

my_sequences:
  - [1, 2, 3]
  - [4, 5, 6]
  -  
    - 7
    - 8
    - 9
    - 0 

---

Json Preview

{
  "my_sequences": [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9, 0]
  ]
}

Jack: {
    hr: 65, 
    avg: 0.278
}

Jess: {
    hr: 63,
    avg: 0.288
}

---

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{
  "jack": {
    "hr": 65,
    "avg": 0.278
  },
  "Jess": {
    "hr": 63,
    "avg": 0.288
  }
}

Jack:
  id: 1
  name: Franc
  salary: 25000
  hobby:
    - a
    - b
  location: {
      country: "A", 
      city: "A-A"
  }

---

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{
  "Jack": {
    "id": 1,
    "name": "Franc",
    "salary": 25000,
    "hobby": [
      "a",
      "b"
    ],
    "location": {
      "country": "A",
      "city": "A-A"
    }
  }
}

set1: !!set
  ? one
  ? two
set2: !!set {'one', "two"}

---

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{
  "set1": {
    "one": null,
    "two": null
  },
  "set2": {
    "one": null,
    "two": null
  }
}

ordered: !!omap
- Jack: 65
- Jess: 63
- Messi: 58

---

Json Preview

{
  "ordered": [
    {
      "Jack": 65
    },
    {
      "Jess": 63
    },
    {
      "Messi": 58
    }
  ]
}

• Sequences aka arrays or lists
• Scalars aka strings or numbers
• Mappings aka hashes or dictionaries

Numberic

• \x12 (8-bit)
• \u1234 (16-bit)
• \U00102030 (32-bit)

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Protective

• \\ (\)
• \" (")
• \ ( )
• \<TAB> (TAB)

---

C

• \0 (NUL)
• \a (BEL)
• \b (BS)
• \f (FF)
• \n (LF)
• \r (CR)
• \t (TAB)
• \v (VTAB)

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Additional

• \e (ESC)
• \_ (NBSP)
• \N (NEL)
• \L (LS)
• \P (PS)