我可以停止std :: cout flushing on“\\\<br/>”？ [英] Can I stop std::cout flushing on &quot;\n&quot;?

问题描述

根据这篇文章 std :: cout will当它附加到交互式设备（例如终端窗口）时，自动刷新 \\\
。否则（例如，当被管道传递到文件时），它将充分缓冲并只在 .flush（）或 std :: endl 。

According to to this post std::cout will automatically flush on \n when it is attached to an interactive device (e.g. a terminal window). Otherwise (e.g. when being piped to a file) it will act fully buffered and will only flush on .flush() or std::endl.

有没有办法在Microsoft Visual C ++中覆盖此行为，以便我可以选择是否需要完全缓冲或行缓冲模式？ p>

Is there a way to override this behaviour in Microsoft Visual C++ so that I can select whether I want fully buffered or line buffered mode?

推荐答案

与anon的（2009年4月28日）答案相反，这个行为与操作系统或控制台软件无关。

Contrary to anon's (Apr 28 '09) answer, this behavior has nothing to do with the operating system or "console software."

C ++的< iostream> 流设计为可与C的< stdio .h> 流。目标是允许使用 std :: cout 与 printf / puts 。为了实现这一点， cd> stdout c实现 std :: cout ' streambuf code> stream。实际上，当标准输出附加到终端设备时，C的 stdout 是行缓冲的。

C++'s <iostream> streams are designed to be interoperable with C's <stdio.h> streams. The goal is to allow uses of std::cout to be intermixed with uses of printf/puts. To achieve this, std::cout's streambuf is implemented atop C's stdout stream. It is actually C's stdout that is line-buffered when the standard output is attached to a terminal device.

可以调用 std :: ios_base :: sync_with_stdio（false） （在您的程序使用任何C ++的标准I / O流之前）告诉C ++流库与底层文件描述符直接通信，而不是在C的流库上层。这避免了C的 stdout 流，并加速了C ++的I / O流，但是两个库不再混用。

You can call std::ios_base::sync_with_stdio(false) (before your program uses any of C++'s standard I/O streams) to tell the C++ streams library to communicate directly with the underlying file descriptors rather than layering atop C's streams library. This avoids C's stdout stream entirely and speeds up C++'s I/O streams at the cost of the two libraries no longer mixing well.

另一种方法是通过调用 stdout 设置为完全缓冲c / setvbufrel =nofollow> std :: setvbuf（stdout，nullptr，_IOFBF，BUFSIZ） 。然后，即使 std :: cout 仍在通过 stdout 写入，您将不会有 stdout 在每个换行符后刷新。

An alternative is to unconditionally set stdout to fully buffered by calling std::setvbuf(stdout, nullptr, _IOFBF, BUFSIZ). Then, even though std::cout is still writing through stdout, you will not have stdout flushing after every newline.

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