从 erlang-sqlite3 端口接收的消息

Question

Erlang-sqlite3 使用端口驱动程序连接 SQLite 数据库，并且 从端口接收消息：

wait_result(Port) ->
  receive
    {Port, Reply} ->
      % io:format("Reply: ~p~n", [Reply]),
      Reply;
    {error, Reason} ->
      io:format("Error: ~p~n", [Reason]),
      {error, Reason};
    _Else ->
      io:format("Else: ~p~n", [_Else]),
      _Else
  end.

我认为来自端口的消息应该类似于 this：

{Port,{data,Data}}    Data is received from the external program.
{Port,closed}         Reply to Port ! {Pid,close}.
{Port,connected}      Reply to Port ! {Pid,{connect,NewPid}}
{'EXIT',Port,Reason}  If the port has terminated for some reason.

因此，当取消注释 {Port, Reply} 子句中的 io:format 行时，我应该会看到 {data, .. .} 获取实际回复。我不；相反，我看到（对于 test.erl）

Reply: {ok,101}
Reply: [{columns,["name"]},{rows,[{<<"user">>}]}]
Reply: [{columns,["sql"]},
        {rows,[{<<"CREATE TABLE user (id INTEGER PRIMARY KEY, name TEXT, age INTEGER, wage INTEGER)">>}]}]
Reply: {id,1}
Reply: {id,2}
Reply: [{columns,["id","name","age","wage"]},
        {rows,[{1,<<"abby">>,20,2000},{2,<<"marge">>,30,2000}]}]
Reply: [{columns,["id","name","age","wage"]},{rows,[{1,<<"abby">>,20,2000}]}]
Reply: [{columns,["id","name","age","wage"]},
        {rows,[{1,<<"abby">>,20,2000},{2,<<"marge">>,30,2000}]}]
Reply: {ok,101}
Reply: [{columns,["id","name","age","wage"]},{rows,[{1,<<"abby">>,20,2000}]}]
Reply: {ok,101}

1. 我哪里出错了？
2. 我收到的端口错误消息是否类似于 {'EXIT',Port,Reason}？

Answer 1

看来您的进程和端口之间涉及另一个进程，它负责解码真实端口消息。你确定那个港口真的是港口吗？尝试 io:format("Port: ~p~n", [Port]) 如果您会看到类似 #Port<0.500> 的内容，则它是端口，如果它类似于 <0.38.0> 中间有一个人。

Answer 2

http://www.erlang.org/doc/apps/erts 中的相关示例/driver.html 是最后一个。事实证明，当使用driver_output_term时，该术语是由其自身发送的：

receive
    Result ->
        Result
end.

而不是

receive
    {Port, {data, Result}} ->
        Result
end.