chdir

# File lib/net/ftp.rb, line 666
    def chdir(dirname)
      if dirname == ".."
        begin
          voidcmd("CDUP")
          return
        rescue FTPPermError
          if $![0, 3] != "500"
            raise FTPPermError, $!
          end
        end
      end
      cmd = "CWD " + dirname
      voidcmd(cmd)
    end