YAML stands for “YAML Ain’t Markup Language,” and it’s quickly becoming the go-to format for configuration files and data exchange. This guide offers a clear and concise explanation of YAML’s syntax, making it easy for beginners to understand and use.It is commonly used for configuration files and data exchange in various applications, especially in contexts where human readability is a priority. YAML is often used in conjunction with scripting languages, configuration management tools, and data serialization libraries.
Key YAML Indicators:
- Collections: Identify lists (
[]) and dictionaries ({}). - Scalars: Learn about different ways to represent strings (including quotes, block and folded styles).
- Aliases & Tags: Discover how to reuse data elements (
&) and define data types (!). - Documents: Understand document structure with indicators like
---and.... - Comments & Special Keys: Explore commenting (
#) and merging keys (<<).
Core YAML Data Types:
- Mappings (
!!map): Represent key-value pairs, similar to dictionaries. - Sequences (
!!seq): Ordered collections of items, like lists or arrays. - Strings (
!!str): Define text data, supporting Unicode characters.
More Advanced YAML Types:
- Sets (
!!set): Unordered collections of unique elements. - Ordered Maps (
!!omap): Maintain insertion order for key-value pairs.
Language Independent Scalars:
- Null (
~): Represents the absence of a value. - Numbers: Define integers (decimal, hexadecimal, octal) and floating-point numbers.
- Booleans (
true,false): Represent true or false values. - Binary Data: Encode binary data using Base64 encoding (
? !!binary).
Escape Codes:
- YAML provides a rich set of escape codes to represent special characters within strings.
This is just a starting point! YAML offers many more features, making it a powerful and versatile data format. With this guide, you’re well on your way to mastering YAML and unlocking its potential in your projects.
%YAML 1.1 # Reference card
---
Collection indicators:
'? ' : Key indicator.
': ' : Value indicator.
'- ' : Nested series entry indicator.
', ' : Separate in-line branch entries.
'[]' : Surround in-line series branch.
'{}' : Surround in-line keyed branch.
Scalar indicators:
'''' : Surround in-line unescaped scalar ('' escaped ').
'"' : Surround in-line escaped scalar (see escape codes below).
'|' : Block scalar indicator.
'>' : Folded scalar indicator.
'-' : Strip chomp modifier ('|-' or '>-').
'+' : Keep chomp modifier ('|+' or '>+').
1-9 : Explicit indentation modifier ('|1' or '>2').
# Modifiers can be combined ('|2-', '>+1').
Alias indicators:
'&' : Anchor property.
'*' : Alias indicator.
Tag property: # Usually unspecified.
none : Unspecified tag (automatically resolved by application).
'!' : Non-specific tag (by default, "!!map"/"!!seq"/"!!str").
'!foo' : Primary (by convention, means a local "!foo" tag).
'!!foo' : Secondary (by convention, means "tag:yaml.org,2002:foo").
'!h!foo': Requires "%TAG !h! <prefix>" (and then means "<prefix>foo").
'!<foo>': Verbatim tag (always means "foo").
Document indicators:
'%' : Directive indicator.
'---': Document header.
'...': Document terminator.
Misc indicators:
' #' : Throwaway comment indicator.
'`@' : Both reserved for future use.
Special keys:
'=' : Default "value" mapping key.
'<<' : Merge keys from another mapping.
Core types: # Default automatic tags.
'!!map' : { Hash table, dictionary, mapping }
'!!seq' : { List, array, tuple, vector, sequence }
'!!str' : Unicode string
More types:
'!!set' : { cherries, plums, apples }
'!!omap': [ one: 1, two: 2 ]
Language Independent Scalar types:
{ ~, null } : Null (no value).
[ 1234, 0x4D2, 02333 ] : [ Decimal int, Hexadecimal int, Octal int ]
[ 1_230.15, 12.3015e+02 ]: [ Fixed float, Exponential float ]
[ .inf, -.Inf, .NAN ] : [ Infinity (float), Negative, Not a number ]
{ Y, true, Yes, ON } : Boolean true
{ n, FALSE, No, off } : Boolean false
? !!binary >
R0lG...BADS=
: >-
Base 64 binary value.
Escape codes:
Numeric : { "\x12": 8-bit, "\u1234": 16-bit, "\U00102030": 32-bit }
Protective: { "\\": '\', "\"": '"', "\ ": ' ', "\<TAB>": TAB }
C : { "\0": NUL, "\a": BEL, "\b": BS, "\f": FF, "\n": LF, "\r": CR,
"\t": TAB, "\v": VTAB }
Additional: { "\e": ESC, "\_": NBSP, "\N": NEL, "\L": LS, "\P": PS }