Capturing cout in Visual Studio 2005 output window?

I've finally implemented this, so I want to share it with you:

#include <vector> #include <iostream> #include <windows.h> #include <boost/iostreams/stream.hpp> #include <boost/iostreams/tee.hpp> using namespace std; namespace io = boost::iostreams; struct DebugSink { typedef char char_type; typedef io::sink_tag category; std::vector<char> _vec; std::streamsize write(const char *s, std::streamsize n) { _vec.assign(s, s+n); _vec.push_back(0); // we must null-terminate for WINAPI OutputDebugStringA(&_vec[0]); return n; } }; int main() { typedef io::tee_device<DebugSink, std::streambuf> TeeDevice; TeeDevice device(DebugSink(), *cout.rdbuf()); io::stream_buffer<TeeDevice> buf(device); cout.rdbuf(&buf); cout << "hello world!\n"; cout.flush(); // you may need to flush in some circumstances } 

BONUS TIP: If you write:

X:\full\file\name.txt(10) : message 

to the output window and then double-click on it, then Visual Studio will jump to the given file, line 10, and display the 'message' in status bar. It's very useful.

You can capture the output of cout like this, for example:

std::streambuf* old_rdbuf = std::cout.rdbuf(); std::stringbuf new_rdbuf; // replace default output buffer with string buffer std::cout.rdbuf(&new_rdbuf); // write to new buffer, make sure to flush at the end std::cout << "hello, world" << std::endl; std::string s(new_rdbuf.str()); // restore the default buffer before destroying the new one std::cout.rdbuf(old_rdbuf); // show that the data actually went somewhere std::cout << s.size() << ": " << s; 

Magicking it into the Visual Studio 2005 output window is left as an exercise to a Visual Studio 2005 plugin developer. But you could probably redirect it elsewhere, like a file or a custom window, perhaps by writing a custom streambuf class (see also boost.iostream).

You can't do this.

If you want to output to the debugger's output window, call OutputDebugString.

I found this implementation of a 'teestream' which allows one output to go to multiple streams. You could implement a stream that sends data to OutputDebugString.

A combination of ben's answer and Mike Dimmick's: you would be implementing a stream_buf_ that ends up calling OutputDebugString. Maybe someone has done this already? Take a look at the two proposed Boost logging libraries.

Is this a case of the output screen just flashing and then dissapearing? if so you can keep it open by using cin as your last statement before return.

Also, depending on your intentions, and what libraries you are using, you may want to use the TRACE macro (MFC) or ATLTRACE (ATL).

Write to a std::ostringsteam and then TRACE that.

std::ostringstream oss; oss << "w:=" << w << " u=" << u << " vt=" << vt << endl; TRACE(oss.str().data());