freopen() 等效于 C++ 流 [英] freopen() equivalent for c++ streams

问题描述

当使用 c 风格的 i/o 编程时，我有时会使用 freopen() 重新打开 stdin 以进行测试，这样我就不必一遍又一遍地重新输入输入.我想知道 c++ i/o 流是否有等价物.另外，我知道我可以使用管道在命令行/终端/任何东西上重定向它，但我想知道是否有办法在我的代码中做到这一点(因为如你所见，我对cl/t/w).

When programming with c-style i/o I sometimes use freopen() to reopen stdin for testing purposes so that I don't have to retype the input over and over. I was wondering if there is an equivalent for c++ i/o streams. Also, I know that I can use pipes to redirect it on the command line/terminal/whateveritis but I was wondering if there was a way to do it inside my code (because as you can see, I'm not very knowledgeable about the cl/t/w).

推荐答案

freopen 也适用于 cin 和 cout.无需搜索新内容.

freopen also works with cin and cout. No need to search for something new.

freopen("input.txt", "r", stdin); // redirects standard input
freopen("output.txt", "w", stdout); // redirects standard output

int x;
cin >> x; // reads from input.txt
cout << x << endl; // writes to output.txt

来自 C++ 标准 27.3.1:

From C++ standard 27.3.1:

对象cin控制来自与对象stdin关联的流缓冲区的输入，在中声明.

The object cin controls input from a stream buffer associated with the object stdin, declared in <cstdio>.

所以根据标准，如果我们重定向stdin，它也会重定向cin.cout 反之亦然.

So according to the standard, if we redirect stdin it will also redirect cin. Vice versa for cout.

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