Hi,
According to to this post std::cout will automatically flush on \n when it is attached to an interactive device (e.g. a terminal window). Otherwise (e.g. when being piped to a file) it will act fully buffered and will only flush on .flush() or std::endl.
Is there a way to override this behaviour in Microsoft Visual C++ so that I can select whether I want fully buffered or line buffered mode?
This is not an issue with C++ (there is no language requirement that \n flushes anything) but with your operating system and/or console software. If the console wants to flush its buffer when it sees a newline, then it can, and I would guess that most do so. Note that it is important to differentiate between the C++ runtime's buffers (which can be to some extent controlled from your C++ cide) and the buffers of the console application (over which it has no control).
FYI, there is a flag in the standard iostream library called unitbuf which if set causes the buffers to be flushed after each output operation. It is set, for example, for the std::cerr stream. This has nothing to do with the '\n' character however, as you can output multiple '\n' s iin a single operation.
An implementation is free to flush whenever it feels it is appropriate. It varies from vendor to vendor whether they flush on \n or not.
I can see something called ios_base& nounitbuf(ios_base& str); from my C++0x draft. Give it a shot. This is about the only thing that standard C++ gives you.