使用cout或cerr在重定向到文件后输出到控制台

问题描述：

将cout或cerr重定向到文件是很容易的。我可以使用它将第三方输出重定向到一个文件。但是，在我将第三方输出重定向到一个文件后，如何使用cout自己输出到控制台？

Redirecting cout or cerr to a file is easy enough. I can use this to redirect third party output to a file. However, after I have redirected the third party output to a file, how do I then use cout myself to output to the console?

答

p>我是RAII的好粉丝，所以我曾经写过这个小帮手类。它将重定向流，直到它超出范围，此时它恢复原始缓冲区。相当方便。：）

I'm a great fan of RAII, so I once wrote this small helper class. It will redirect the stream until it goes out of scope, at which point it restores the original buffer. Quite handy. :)

class StreamRedirector {
public:
    explicit StreamRedirector(std::ios& stream, std::streambuf* newBuf) :
        savedBuf_(stream.rdbuf()), stream_(stream)
    {
        stream_.rdbuf(newBuf);
    }

    ~StreamRedirector() {
        stream_.rdbuf(savedBuf_);
    }

private:
    std::streambuf* savedBuf_;
    std::ios& stream_;
};

可以这样使用：

using namespace std;
cout << "Hello stdout" << endl;
{
    ofstream logFile("log.txt");
    StreamRedirector redirect(cout, logFile.rdbuf());
    cout << "In log file" << endl;
}
cout << "Back to stdout" << endl;

使用cout或cerr在重定向到文件后输出到控制台

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