tree implement in ruby

Just for fun, but it work well.

 01 #!/usr/bin/env ruby
 02 # 
 03 # 
 04 
 05 
 06 def tree(dirname, indent = "  |")
 07     puts dirname + "/" if indent == "  |"
 08     dir = Dir.open dirname
 09     for f in dir
 10         if f == "." || f == ".."
 11             next
 12         elsif File.directory? dirname+"/"+f
 13             puts indent + "-" + f + "/"
 14             tree( dirname+"/"+f, indent+"  |")
 15         else
 16             puts indent + "-" + f
 17         end
 18     end
 19 end
 20 
 21 tree (ARGV[0]? ARGV[0] : ".")