将函数输出重定向到/ dev / null [英] Redirecting function output to /dev/null

问题描述

我正在使用正在向 cout 或 cerr 打印警告消息的库。我不想让这个警告消息到达我的程序的输出。如何捕获此输出并将其放入 / dev / null 或类似的？

I am using a library that is printing a warning message to cout or cerr. I don't want this warning message to reach the output of my program. How can I catch this output and put it into /dev/null or similar?

MWE：

#include <iostream>

void foo()
{
    std::cout << "Boring message. " << std::endl;
};

int main()
{
    foo();
    std::cout << "Interesting message." << std::endl;
    return 0;
}

输出应为：

Interesting message.

---

如何修改 main 以获得所需的输出？ （ foo 不得更改。）

---

How should I modify main to get the desired output? (foo must not be changed.)

freopen（）和 fclose（stdout）如何在Windows应用程序中将stdout重定向到某个可见的显示？ >。结果是什么也不打印。

I tried using freopen() and fclose(stdout) as suggested in this question How can I redirect stdout to some visible display in a Windows Application?. The result is that nothing is printed.

推荐答案

如果你确定这个东西不会重定向输出（例如到 / dev / tty / / code>，这将是标准输出再次）（我不认为），你可以重定向之前调用他们。

If you are sure that thing does not redirect output (e.g. to /dev/tty/, which would be standard-out again) (which I don't think), you could redirect before calling them.

#include <iostream>
#include <sstream>

void foobar() { std::cout << "foobar!\nfrob!!"; }

int main () {    
    using namespace std;

    streambuf *old = cout.rdbuf(); // <-- save        
    stringstream ss;

    cout.rdbuf (ss.rdbuf());       // <-- redirect
    foobar();                      // <-- call
    cout.rdbuf (old);              // <-- restore

    // test
    cout << "[[" << ss.str() << "]]" << endl;
}

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