C ++：重定向STDOUT [英] C++: Redirecting STDOUT

问题描述

在我的应用程序中，我想重定向通常去到stdout流的输出到我定义的函数。我读到您可以将stdio重定向到某个文件，为什么不将该文件重定向到某个功能？

In my application, I want to redirect the output that would normally go to the stdout stream to a function I define. I read that you can redirect stdio to a file, so why not to a function?

例如：

void MyHandler( const char* data );

//<<Magical redirection code>>

printf( "test" );
std::cout << "test" << std::endl;

//MyHandler should have been called with "test" twice, at this point

• 如何实现此类似行为？



推荐答案

p> @Konrad Rudolph是对的，你可以完全做到这一点，容易，至少cout / cerr / clog。你甚至不需要自己的streambuf实现，只需使用ostringstream。

@Konrad Rudolph is right, you can totally do this, easily, at least for cout/cerr/clog. You don't even need your own streambuf implementation, just use an ostringstream.

// Redirect cout.
streambuf* oldCoutStreamBuf = cout.rdbuf();
ostringstream strCout;
cout.rdbuf( strCout.rdbuf() );

// This goes to the string stream.
cout << "Hello, World!" << endl;

// Restore old cout.
cout.rdbuf( oldCoutStreamBuf );

// Will output our Hello World! from above.
cout << strCout.str();

同样的事情适用于cerr和clog，但在我的经验中，不适用于stdout / stderr一般，所以printf不会输出。 cout去stdout，但重定向cout不会重定向所有的stdout。至少，这是我的经验。

Same thing works for cerr and clog, but in my experience that will NOT work for stdout/stderr in general, so printf won't output there. cout goes to stdout, but redirecting cout will not redirect all stdout. At least, that was my experience.

如果数据量预计很小，freopen / setbuf的东西工作正常。我最后做的鸽友dup / dup2的东西重定向到管道。

If the amount of data is expected to be small, the freopen/setbuf thing works fine. I ended up doing the fancier dup/dup2 thing redirecting to a pipe.

更新：我写了一篇博客文章，显示我最后使用的dup2方法，您可以阅读此处。它是为OS X编写的，但可能在其他Unix风格中工作。我真的怀疑它会工作在Windows。同一事件的可可版本此处。

Update: I wrote a blog post showing the dup2 method I ended up using, which you can read here. It's written for OS X, but might work in other Unix flavors. I seriously doubt it would work in Windows. Cocoa version of the same thing here.

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