Question

我有以下代码：

file:write(FileId, Packet),
file:close(FileId),
{ok, FileId1} = file:open("tmp/" ++ integer_to_list(Summ), [read]),
A = file:read_file("tmp/" ++ integer_to_list(Summ)),
{_, B} = A,
io:format(binary_to_list(B));

在功能结束时，我看到io:format B输出。但如果我这样做：

file:write(FileId, Packet),
file:close(FileId),
{ok, FileId1} = file:open("tmp/" ++ integer_to_list(Summ), [read]),
A = file:read_file("tmp/" ++ integer_to_list(Summ)),
{_, B} = A,
S = binary_to_list(B),
io:format(S);

io:format nothing output. Why?

谢谢。

Answer 1

您可能不应该依赖单参数io:format/1函数：

3> B="helo\n".  
"helo\n"
4> io:format(B).
helo
ok
5> C="~p".
"~p"
6> io:format(C).
** exception exit: {badarg,[{io,format,[<0.26.0>,"~p",[]]},
                            {erl_eval,do_apply,5},
                            {shell,exprs,6},
                            {shell,eval_exprs,6},
                            {shell,eval_loop,3}]}
     in function  io:o_request/3

如果参数包含任何格式请求，则io:format调用可能会死亡。我建议使用格式字符串，例如~p~n or ~w~n：

1> C="~p".
"~p"
2> io:format("~p~n", [C]).
"~p"
ok

Answer 2

它在这方面做得非常好：

3> {ok, FileId1} = file:open("tmp/" ++ integer_to_list(Summ), [read]),
3> A = file:read_file("tmp/" ++ integer_to_list(Summ)),
3> {_, B} = A,
3> S = binary_to_list(B),
3> io:format(S).
1213

Answer 3

io:format/1的参数是格式字符串，它不能包含任何需要参数的格式化控制序列。如果发生这种情况，则会生成错误。要输出原始可打印字符，请使用io:put_chars/1。

二进制列出奇怪的输出

3 个答案: