• Too many ways for process in Ruby (`,open3,spawn,system) • Need environment variables support to system method for cross build. • Thank all the developers of mrbgems I used. • Mainly port of Dir.glob (and the great idea): https://github.com/gromnitsky/mruby-dir-glob • IIJ for many stable mrbgems. • I want keyword arguments(because of FileUtils) • Actually I implemented it: https://github.com/mruby/mruby/pull/3629