fmt¶

cfnrain fmt formats templates. It sorts the sections and properties in a fixed order, uses the short form of intrinsic functions (!Sub, !Ref), and keeps your YAML comments. format is an alias.

Input, bucket.json:

{"Resources":{"Bucket":{"Properties":{"BucketName":{"Fn::Sub":"${AWS::StackName}-data"}},"Type":"AWS::S3::Bucket"}},"Outputs":{"Name":{"Value":{"Ref":"Bucket"}}}}

cfnrain fmt bucket.json

Output:

Resources:
  Bucket:
    Type: AWS::S3::Bucket
    Properties:
      BucketName: !Sub ${AWS::StackName}-data

Outputs:
  Name:
    Value: !Ref Bucket

Flag	What it does
`-w`, `--write`	Write the result back to the file
`-v`, `--verify`	Do not print. Exit with status 0 if the file is already formatted, and 1 if it is not.
`-j`, `--json`	Write JSON instead of YAML
`-u`, `--unsorted`	Keep the original order of sections and properties
`--uncdk`	Remove CDK metadata, simplify logical IDs, and turn `Fn::Join` into `Fn::Sub`
`--node-style`	Choose how to write YAML values: `tagged`, `doublequoted`, `singlequoted`, `literal`, `folded`, `strict-boolean`, `quotescalars`, `original` or `flow`
`-p`, `--pkl`	Write Pkl instead of YAML
`--pkl-basic`	With `--pkl`, do not use the Pkl modules of the `cfn` package
`--pkl-package`	With `--pkl`, the alias or full URI of the Pkl package. The default is `@cfn`.
`--datamodel`	Print the internal YAML data model. This is for debugging cfnrain.

With no file names, fmt reads standard input.

Format every template in place:

cfnrain fmt -w templates/*.yaml

Fail a CI job when a template is not formatted:

cfnrain fmt -v templates/app.yaml

templates/app.yaml: would reformat

--verify compares the input text with the formatted YAML. A JSON file never passes unless you also give -j.