@shogomuranushi さんが拙作の j2y で CloudFormation のテンプレートを作る話を書いてくれたので、なんか他の使い方ないかなーと思って書いてみます。

AWS CLIの表示形式は json, table, text が選べますが、 yaml は選択肢にありません。

そこで、 j2y を使ってAWS CLIの出力をYAMLにしてみます。

$ j2y -e "$(aws ec2 describe-regions)"
Regions:
- Endpoint: ec2.eu-west-1.amazonaws.com
  RegionName: eu-west-1
- Endpoint: ec2.ap-southeast-1.amazonaws.com
  RegionName: ap-southeast-1
- Endpoint: ec2.ap-southeast-2.amazonaws.com
  RegionName: ap-southeast-2
- Endpoint: ec2.eu-central-1.amazonaws.com
  RegionName: eu-central-1
- Endpoint: ec2.ap-northeast-2.amazonaws.com
  RegionName: ap-northeast-2
- Endpoint: ec2.ap-northeast-1.amazonaws.com
  RegionName: ap-northeast-1
- Endpoint: ec2.us-east-1.amazonaws.com
  RegionName: us-east-1
- Endpoint: ec2.sa-east-1.amazonaws.com
  RegionName: sa-east-1
- Endpoint: ec2.us-west-1.amazonaws.com
  RegionName: us-west-1
- Endpoint: ec2.us-west-2.amazonaws.com
  RegionName: us-west-2

おお。これなら describe-instances とかの出力結果も少しは見やすいかもですね。

標準入力できるようになりました（from v0.0.8）

$ aws ec2 describe-regions | j2y
Regions:
- Endpoint: ec2.eu-west-1.amazonaws.com
  RegionName: eu-west-1
- Endpoint: ec2.ap-southeast-1.amazonaws.com
  RegionName: ap-southeast-1
- Endpoint: ec2.ap-southeast-2.amazonaws.com
  RegionName: ap-southeast-2
- Endpoint: ec2.eu-central-1.amazonaws.com
  RegionName: eu-central-1
- Endpoint: ec2.ap-northeast-2.amazonaws.com
  RegionName: ap-northeast-2
- Endpoint: ec2.ap-northeast-1.amazonaws.com
  RegionName: ap-northeast-1
- Endpoint: ec2.us-east-1.amazonaws.com
  RegionName: us-east-1
- Endpoint: ec2.sa-east-1.amazonaws.com
  RegionName: sa-east-1
- Endpoint: ec2.us-west-1.amazonaws.com
  RegionName: us-west-1
- Endpoint: ec2.us-west-2.amazonaws.com
  RegionName: us-west-2