Building JAR bundle exec warble java -jar warbler-example.jar Environment JRuby version ruby --version jruby 9.1.17.0 (2.3.3) 2018-04-20 d8b1ff9 OpenJDK 64-Bit Server VM 25.232-b09 on 1.8.0_232-b09 +jit [darwin-x86_64]