http://ruby-doc.org/core-2.1.2/File.html#method-c-dirname
(1)basename(file_name [, suffix] ) → base_name
Returns the last component of the filename given in file_name, which can be formed using bothFile::SEPARATOR and File::ALT_SEPARATOR as the separator when File::ALT_SEPARATOR is not nil. If suffix is given and present at the end of file_name, it is removed.
File.basename("/home/gumby/work/ruby.rb") #=> "ruby.rb" File.basename("/home/gumby/work/ruby.rb", ".rb") #=> "ruby"
(2)dirname(file_name) → dir_name
Returns all components of the filename given in file_name except the last one. The filename can be formed using both File::SEPARATOR and File::ALT_SEPARATOR as the separator whenFile::ALT_SEPARATOR is not nil.
File.dirname("/home/gumby/work/ruby.rb") #=> "/home/gumby/work"
原文：http://www.cnblogs.com/iwangzheng/p/3942072.html