1. Download the Java JAR (https://oss.sonatype.org/content/repositories/snapshots/org/openapitools/openapi-generator-cli/4.1.3-SNAPSHOT/openapi-generator-cli-4.1.3-20190913.092234-8.jar)

2. Rename the JAR as "openapi-generator-cli.jar"

3. Run the following command to generate a Ruby API client for the Petstore API (https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml):

Mac/Linux:

$ java -jar openapi-generator-cli.jar generate -g nim -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml -o /var/tmp/nim/

Windows:

$ java -jar openapi-generator-cli.jar generate -g nim -i https://raw.githubusercontent.com/OpenAPITools/openapi-generator/master/modules/openapi-generator/src/test/resources/2_0/petstore.yaml -o C:\tmp\nim

If you've any feedback or question, please let us know via https://github.com/OpenAPITools/openapi-generator/issues/new

Thanks for the new generator by Hideki Okamoto (https://github.com/hokamoto)

Ref: https://github.com/OpenAPITools/openapi-generator/pull/3879