Erlang文件截斷

Question

我正在嘗試編寫一個基本的Erlang程序，該程序在一個進程中讀取文件，然后在另一個進程中寫入文件。 我發現有時輸出文件會被截斷。

例如我寫了eunit test。 如果我運行單個測試drive_test：write_file_test（），則輸出將正確寫入。 但是運行drive_test：test（）每次都會在不同的位置截斷輸出文件。

我需要做一些特別的事情來確保進程在關閉之前完成寫操作嗎？

drive.erl：

-module(drive).
-include("library.hrl").
-export([init/1]).

init(Drive) ->
  loop(Drive).

loop(Drive) ->
  receive
    {write, Data} ->
      write(Drive,Data),
      loop(Drive);
    close -> 
      close(Drive)
  end.

write(Drive,Data) ->
  %io:format("~p", [Data]),
  Handler = Drive#drive.volume,
  file:write(Handler, [Data]).

close(Drive) ->
  Handler = Drive#drive.volume,
  file:close(Handler),
  io:format("closed ~w~n", [Drive]).

drive_test.erl

-module(drive_test).
-include_lib("eunit/include/eunit.hrl").
-include("library.hrl").

startupShutdown_test() ->
  DrivePid = spawn(drive,init,[#drive{number=1}]),
  DrivePid ! close.

write_basic_test() ->
  {ok, F} =file:open("test/library/eunit.txt", write),
  DrivePid = spawn(drive,init,[#drive{number=1,volume=F}]),
  DrivePid ! {write, "Some Data"},
  DrivePid ! close.

write_file_test() ->
  {ok, Fin} = file:open("cathedral.pdf", read),
  {ok, Fout} =file:open("test/library/eunit2.txt", write),
  DrivePid = spawn(drive,init,[#drive{number=1,volume=Fout}]),
  write_file( Fin, DrivePid),
  DrivePid ! close.

write_file(F, DrivePid ) ->
  Rd = file:read(F, 256),
  case Rd of
    {ok, Data} -> 
      DrivePid ! {write, Data}, 
      write_file(F, DrivePid );
    eof -> file:close(F);
    _ -> ?_assert(false)
  end.

截斷的文件：

$ ls -l cathedral.pdf test/library/eunit2.txt
-rwx------+ 1 218879 Sep 16 22:21 cathedral.pdf
-rwxr-xr-x  1  60928 Dec 17 09:31 test/library/eunit2.txt

Answer 1

這很可能是與“時序”相關的問題。 我懷疑這與“ Eunit”的處理方式有關：“ EUnit”可能沒有給模塊足夠的時間在退出並終止所有進程之前close 。