This article assumes you know the basics about YAML, including the following.
In a YAML serialization, whitespace matters and tabs are not allowed.[2]
The elementary particles of YAML are called scalars. A YAML scalar is also known as an atom and is usually a boolean, a number, or a string.
For an overview of YAML, see Infinite Ink’s YAML Includes Atoms, Maps, and Lists.
In this article, a leading or trailing space in a YAML line is represented with a teal BULLET character. For example:
this line begins with 0 spaces •this line begins with 1 space ••this line begins with 2 spaces •••this line begins with 3 spaces this line ends with 0 spaces this line ends with 1 space• this line ends with 2 spaces•• this line ends with 3 spaces••• •this line both begins and ends with 1 space•
The front matter of the source of this article includes this line:
title: 'YAML’s Folded Block Scalars: A Way to Avoid Quoting Most Strings'
The value of this YAML key-value pair is this:
'YAML’s Folded Block Scalars: A Way to Avoid Quoting Most Strings'
This is a single-quoted single-line flow scalar.
‼ | The
value of this title
must be quoted
because it contains a colon followed by a space
(:•),
which is
a character sequence
that
can have
a special meaning in
YAML.[3] |
To learn about YAML flow scalars, see yaml.org/spec/1.2.2/#73-flow-scalar-styles.
The following three lines are an equivalent way to specify this article’s title.
title: >- ••YAML’s Folded Block Scalars: ••A Way to Avoid Quoting Most Strings
The value of this YAML key-value pair is the following folded block scalar.
>- ••YAML’s Folded Block Scalars: ••A Way to Avoid Quoting Most Strings
The second and third lines contain the scalar’s content. The first line is the block scalar header and contains the following indicators.
| Indicator | Meaning |
|---|---|
| block scalar style is folded |
| chomping method is strip |
💡 | If
a block scalar’s content contains an ASCII quotation mark (' or "),
it will not have any special meaning
and will be interpreted as a literal quotation mark. |
To learn about block scalars, see yaml.org/spec/1.2.2/#81-block-scalar-styles.
One of the things I like about YAML is that you do not need to quote most strings. But, if a string is a flow scalar and it either…
contains a
special character[3]
or
special
character sequence
(:•
or
•#),
or looks like a number or boolean,
it must be quoted.
You can
avoid quoting a string
by
specifying it
using a block scalar.
Because of this,
I’m in the midst of converting
Infinite Ink’s quoted
flow scalars
to
block scalars. For example,
in
Infinite Ink’s
config.yaml,
I changed this:
cacheDir: 'C:\Hugo_cache_infiniteink'
to this:
cacheDir: >-
••C:\Hugo_cache_infiniteinkThis is one of the YAML examples discussed on
Infinite Ink’s
YAML Includes Atoms, Maps, and Lists (featuring the string ¯\_(ツ)_/¯).
To learn more about YAML, see…
stackoverflow.com: How do I break a string in YAML over multiple lines?
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