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Command-line YAML, XML, TOML processor - jq wrapper for YAML/XML/TOML documents

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kislyuk/yq

yq: Command-line YAML/XML/TOML processor - jq wrapper for YAML, XML, TOML documents

Installation

pip install yq

Before using yq, you also have to install its dependency, jq. See the jq installation instructions for details and directions specific to your platform.

On macOS, yq is also available on Homebrew: use brew install python-yq.

Synopsis

yq takes YAML input, converts it to JSON, and pipes it to jq:

cat input.yml | yq .foo.bar

Like in jq, you can also specify input filename(s) as arguments:

yq .foo.bar input.yml

By default, no conversion of jq output is done. Use the --yaml-output/-y option to convert it back into YAML:

cat input.yml | yq -y .foo.bar

Mapping key order is preserved. By default, custom YAML tags and styles in the input are ignored. Use the --yaml-roundtrip/-Y option to preserve YAML tags and styles by representing them as extra items in their enclosing mappings and sequences while in JSON:

yq -Y .foo.bar input.yml

yq can be called as a module if needed. With -y/-Y, files can be edited in place like with sed -i:

python -m yq -Y --indentless --in-place '.["current-context"] = "staging-cluster"' ~/.kube/config

Use the --width/-w option to pass the line wrap width for string literals. Use --explicit-start/--explicit-end to emit YAML start/end markers even when processing a single document. All other command line arguments are forwarded to jq. yq forwards the exit code jq produced, unless there was an error in YAML parsing, in which case the exit code is 1. See the jq manual for more details on jq features and options.

Because YAML treats JSON as a dialect of YAML, you can use yq to convert JSON to YAML: yq -y . < in.json > out.yml.

Preserving tags and styles using the -Y (--yaml-roundtrip) option

The -Y option helps preserve custom string styles and tags in your document. For example, consider the following document (an AWS CloudFormation template fragment):

Resources:
  ElasticLoadBalancer:
    Type: 'AWS::ElasticLoadBalancing::LoadBalancer'
    Properties:
      AvailabilityZones: !GetAZs ''
      Instances:
        - !Ref Ec2Instance1
        - !Ref Ec2Instance2
      Description: >-
        Load balancer for Big Important Service.

        Good thing it's managed by this template.

Passing this document through yq -y .Resources.ElasticLoadBalancer will drop custom tags, such as !Ref, and styles, such as the folded style of the Description field:

Type: AWS::ElasticLoadBalancing::LoadBalancer
Properties:
  AvailabilityZones: ''
  Instances:
    - Ec2Instance1
    - Ec2Instance2
  Description: 'Load balancer for Big Important Service.

    Good thing it''s managed by this template.'

By contrast, passing it through yq -Y .Resources.ElasticLoadBalancer will preserve tags and styles:

Type: 'AWS::ElasticLoadBalancing::LoadBalancer'
Properties:
  AvailabilityZones: !GetAZs ''
  Instances:
    - !Ref 'Ec2Instance1'
    - !Ref 'Ec2Instance2'
  Description: >-
    Load balancer for Big Important Service.

    Good thing it's managed by this template.

To accomplish this in -Y mode, yq carries extra metadata (mapping pairs and sequence values) in the JSON representation of your document for any custom tags or styles that it finds. When converting the JSON back into YAML, it parses this metadata, re-applies the tags and styles, and discards the extra pairs and values.

Warning

The -Y option is incompatible with jq filters that do not expect the extra information injected into the document to preserve the YAML formatting. For example, a jq filter that counts entries in the Instances array will come up with 4 entries instead of 2. A filter that expects all array entries to be mappings may break due to the presence of string metadata keys. Check your jq filter for compatibility/semantic validity when using the -Y option.

yq does not support passing YAML comments into the JSON representation used by jq, or roundtripping such comments.

XML support

yq also supports XML. The yq package installs an executable, xq, which transcodes XML to JSON using xmltodict and pipes it to jq. Roundtrip transcoding is available with the xq --xml-output/xq -x option. Multiple XML documents can be passed in separate files/streams as xq a.xml b.xml. Use --xml-item-depth to descend into large documents, streaming their contents without loading the full doc into memory (for example, stream a Wikipedia database dump with cat enwiki-*.xml.bz2 | bunzip2 | xq . --xml-item-depth=2). Entity expansion and DTD resolution is disabled to avoid XML parsing vulnerabilities. Use python -m yq.xq if you want to ensure a specific Python runtime.

TOML support

yq supports TOML as well. The yq package installs an executable, tomlq, which uses the tomlkit library to transcode TOML to JSON, then pipes it to jq. Roundtrip transcoding is available with the tomlq --toml-output/tomlq -t option. Use python -m yq.tomlq if you want to ensure a specific Python runtime.

Compatibility note

This package's release series available on PyPI begins with version 2.0.0. Versions of yq prior to 2.0.0 are distributed by https://github.com/abesto/yq and are not related to this package. No guarantees of compatibility are made between abesto/yq and kislyuk/yq. This package follows the Semantic Versioning 2.0.0 standard. To ensure proper operation, declare dependency version ranges according to SemVer.

Authors

  • Andrey Kislyuk

Links

Bugs

Please report bugs, issues, feature requests, etc. on GitHub.

License

Licensed under the terms of the Apache License, Version 2.0.

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