Ruby的库路径

irb下打入p $即显示出来

如: 

 irb(main):003:0* p $:

["c:/ruby/lib/ruby/site_ruby/1.8", "c:/ruby/lib/ruby/site_ruby/1.8/i386-msvcrt",

 "c:/ruby/lib/ruby/site_ruby", "c:/ruby/lib/ruby/1.8", "c:/ruby/lib/ruby/1.8/i38

6-mswin32", "."]

=> nil