Introduction
JRuby is a Ruby-oriented interpreter based on the Java Virtual Machine (JVM). It combines the simplicity of the Ruby language and the powerful JVM execution mechanism, including full integration with the Java library. jruby.jar is an intermediate product of jruby-core-1.7.27.jar. That is, jruby.jar is compiled from jruby-core-1.7.27.jar.
Parent topic: JRuby Porting Guide (CentOS 7.6)