yq Command-Line Processor

KYaml is a restricted subset of YAML that uses flow-style collections. It is designed to render YAML data in a compact, JSON-like form while retaining YAML-specific features such as comments.

When using KYaml:

• Strings are always output with double quotes.
• Anchors and aliases are expanded into their full values (KYaml does not emit anchors or aliases in its output).

KYaml is a restricted subset of YAML that uses flow-style collections (braces {} and brackets []). It is useful for rendering YAML data in a compact, JSON-like format while still supporting YAML features like comments.

Key characteristics of KYaml output:

• Strings are always double-quoted.
• Anchors and aliases are expanded into concrete values (they are not emitted as anchors/aliases).
• It uses flow-style collections and explicit commas.
• It supports arbitrary nesting of lists and objects.

yq -o=kyaml '.' sample.yml

Use the pipe operator (|) to pass the output of one yq expression as the input to the next. This functions similarly to the pipe operator in bash, allowing you to chain multiple transformations together in a single command.

# Example of chaining operations
yq '.foo | .bar' file.yaml

The flatten operator is used to recursively flatten arrays within a YAML/JSON structure. It takes nested arrays and collapses them into a single-level array.

# Example usage (conceptual)
yq '.path.to.array | flatten' input.yaml

When using -o=shell, yq automatically adapts keys that would be illegal in a shell environment:

• Symbols: Characters like = are replaced with _.
• Whitespace/Controls: Keys containing tabs or other control characters are dropped.
• Non-ASCII: Non-ASCII characters are dropped.
• Accented Characters: Accented Latin letters are normalized via Unicode NFKD (e.g., ñ becomes n).

Aliases (*anchor) and merge anchors (<<: *anchor) can be traversed.

• To traverse the content of an alias, use the splat operator: .b[].
• To traverse a specific key within an alias, use explicit paths: .b.c.
• When using merge anchors, the behavior of key overrides depends on whether --yaml-fix-merge-anchor-to-spec is enabled.

# Traversing aliases with splat
yq '.b[]' sample.yml

# Traversing aliases explicitly
yq '.b.c' sample.yml

Encoder operators transform an object structure into a formatted string. Decoder operators perform the inverse, converting a formatted string back into an object structure. These are useful for processing YAML documents that contain embedded stringified data (like JSON, XML, or CSV).

The and and or operators take two parameters and return a boolean result. The not operator flips a boolean value (true to false, or vice versa).

Note that in yq, non-boolean values have truthiness:

• Strings (including empty strings "") are considered true.
• Numbers (including 0) are considered true.
• null (~) is considered false.

# or example
yq --null-input 'true or false'

# and example
yq --null-input 'true and false'

# not examples
yq --null-input 'true | not'
yq --null-input 'false | not'
yq --null-input '~ | not'