     send scheduler, { :ready, self()}
     receive do
       { :count, file, client } ->
-        send client, { :answer, file, count_word(file), self() }
+        if !File.dir?(file) do # guard節でディレクトリ/ファイルをパターンマッチ出来ない。
+          send client, { :answer, file, count_word(file), self() }
+        else
+          send client, { :answer, file, 0, self() }
+        end
         count(scheduler)
 
       { :shutdown } ->

end

# Execute on 3.1 GHz Intel Core i5
# catではなくて、'do'の数を算出している。
# elixir working_with_multiple_processes09.exs
# [{".working_with_multiple_processes09.exs.swp", 0}, {"working_with_multiple_processes01.ex", 6}, {"working_with_multiple_processes02.ex", 5}, {"working_with_multiple_processes03.ex", 5}, {"working_with_multiple_processes04.ex", 5}, {"working_with_multiple_processes05.ex", 6}, {"working_with_multiple_processes06.ex", 3}, {"working_with_multiple_processes07.ex", 5}, {"working_with_multiple_processes08.exs", 9}, {"working_with_multiple_processes09.exs", 11}]
#
#  #    time(s)
#  1      0.01
#  2      0.00
#  3      0.00
#  4      0.00
#  5      0.01
#  6      0.01
#  7      0.01
#  8      0.00
#  9      0.01
# 10      0.01


  end
end

to_processes = File.ls!("./") #|> Enum.reject(&(File.dir?(&1)))

Enum.each 1..10, fn num_processes ->
  {time, result} = :timer.tc(
