【Yaml】Understand yaml file format

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1. Introduction

YAMLIt is a more user-friendly data serialization language that can be used with most current programming languages.

The syntax of YAML is relatively concise and intuitive, and its feature is to use spaces to express hierarchy. Its biggest advantage is thatData structureTherefore, YAML is more used in writing configuration files, and its files are generally suffixed with .yml.

2. Basic grammar

1. Case sensitivity. Size is regarded as different variables

version: 1.12
Version: 1.12

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2. Use#Indicates comments. Only single line comments are supported

# This is the comment content
# This is another line of comments
version: 1.12

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3. Indentation represents hierarchical relationships。 Use space indentation (the Tab key cannot be used), it doesn't matter how many spaces are indented, but must be left aligned

test: 
     # Indent one
     value_1: 1
     value_2: 2
     value_3:
     					# Indented two
     					value_3_1: 3_1
     					value_3_1: 3_1

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3. Data type

1. String

• No quotation packets are required by default

  strings:
     - Hello without quote # No quotation marks wrapped
     - Hello
      world # After splitting into multiple lines, spaces will be automatically added in the middle.
     - 'Hello with single quotes' # Single quotes package
     - "Hello with double quotes" # double quotes wrap
     - "I am fine. \u263A" # Support Unicode encoding when wrapping with double quotes
     - "\x0d\x0a is \r\n" # Hex encoding is also supported when wrapping with double quotes
     - 'He said: "Hello!"' #Nesting in odd and double quotes"
  

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2. Boolean value

• true、yes(Case-free) is true.false、no(Case-free) "No" and "NO" are false

  boolean:
     - true # True、TRUE
     - yes # Yes、YES
     - false # False、FALSE
     - no # No、NO
  

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3. Numerical type

• Includes integer types and floating point types

  int:
      - 666
      - 0001_0000 # Binary representation
  
  float:
      - 3.14
      - 6.8523015e+5 # Use scientific notation
  

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3. Empty type

• null Null ~Both represent empty, and if the default value is not specified, it is also empty

  kong:
       - null
       - Null
       - ~
       - 
  

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4. Timestamp type

• supportISO 8601Format time data

  date1: 2020-05-26
  date2: 2020-05-26T01:00:00+08:00
  dete3: 2020-05-26T02:00:00.10+08:00
  date4: 2020-05-26 03:00:00.10 +8
  

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5. Type conversion

• use!!Cases type

  a: !!float '666' # !! is a strict type tag
  b: '666' # In fact, double quotes are also considered type converters
  c: !!str 666 # Convert integers to strings
  d: !!str 666.66 # convert floating point numbers into strings
  e: !!str true # convert boolean into string
  f: !!str yes # convert boolean into string
  

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IV. Data structure

1. Object. Key-value correspondence

• Use colon + space:express

   version: 1.12
  

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• Multi-layer nesting

  version: 
       major: 1
       minor: 12
  

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• Supports Flow Style. Braces wrapped, comma separated

  # Normal style
  version: 
       major: 1
       minor: 12
   # Streaming style
   version: {major: 1, minor: 2}
  

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• use?Represents complex objects,keyCan be any type

  # Normal type
  version: 
     major: 1
     minor: 12
  # Complex type Use arrays as keys here, equivalent to {[version_1,version_2]: 1.12}
  ?
   - version_1
   - version_2
  : 1.12
  

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``

2. Array

• The representation is dash plus space

  # equivalent to json {version: [major: 1, minor: 12]}
  version: 
       - major: 1
       - minor: 12
  

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• Supports inline format (Inline Format). Square brackets, separated by commas and spaces

  # equivalent to json {version: [major: 1, minor: 12]}
  # Normal format
  version: 
       - major: 1
       - minor: 12
  # Inline format
  version: [major: 1, minor: 12]
  

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• Multidimensional array (indented represents hierarchical relationship)

  # equivalent to json {version: [major: 1, minor: 12]}
  # Normal format
  version: 
       - 
  	     - 1
  	     - 2
  	     - 3
       - 
  	     - 1
  	     - 2
  	     - 3
  # Inline format
  version: [[1,2,3], [1,2,3]]
  

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Here are some references, 🧡

• Understand YAML
• YAML Schema Reference
• Step by step guide to building a GitHub repository with Azure Pipelines
• YAML: Probably not that perfect