YAML Block Scalars: Handling Multi-line Strings

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YAML block scalars are essential features for managing multi-line strings in YAML configurations. They provide a clean and readable way to represent large text blocks, preserving or folding newlines as needed.

Types of Block Scalars

YAML offers two types of block scalars:

Literal Block Scalar (|): Preserves all newlines within the block.
Folded Block Scalar (>): Folds newlines to spaces, except for empty lines and more-indented lines.

Literal Block Scalar

Literal block scalars are denoted by the pipe character (|). They maintain all line breaks in the text.


description: |
  This is a multi-line
  description that preserves
  line breaks.
  Each line will appear as-is.

Folded Block Scalar

Folded block scalars use the greater-than symbol (>). They convert single line breaks to spaces, creating a single long line.


about: >
  This is a long description
  that will be folded into a
  single line. Empty lines

  create paragraph breaks.

Indentation and Chomping Indicators

Block scalars can be further customized with indentation and chomping indicators:

Indentation: Specify the indentation level with a number after the block scalar indicator.
Chomping: Control trailing newlines with '-' (strip), '+' (keep), or nothing (clip).


example: |2-
  This block is indented by 2 spaces
  and will strip all trailing newlines.

Use Cases

Block scalars are particularly useful for:

Configuration files with multi-line values
Embedding scripts or code snippets
Preserving formatting in text blocks

They're often used in application configurations, Docker files, and Kubernetes manifests.

Best Practices

Choose the appropriate scalar type based on your newline requirements.
Be consistent with indentation within your YAML files.
Use chomping indicators to control trailing newlines effectively.
Consider readability when deciding between block scalars and other multi-line string formats.

Related Concepts

To further enhance your YAML skills, explore these related topics:

Understanding block scalars is crucial for effectively managing complex string data in YAML. They provide a powerful tool for maintaining readability and precision in your configurations.