--- File.dirname(filename)

    filename ΰָΥåʸ
    Ȥ֤ޤåޤޤʤե̾ФƤ
    "."(ȥǥ쥯ȥ)֤ޤ

    :

        p File.dirname("dir/file.ext")    # => "dir"
        p File.dirname("file.ext")        # => "."

    File.basename, File.extname ⻲ȡ

    ruby 1.8 feature

    File.dirname ư SUSv3 [URL:http://www.unix-systems.org/version3/online.html] ˽褦ѹޤ

        p File.dirname("foo/bar/")      # => "foo"  ϡ"foo/bar"
        p File.dirname("foo//bar")      # => "foo"  ϡ"foo/"

