Flushes a stream without locking the thread.
This function is a non-locking version of fflush. It is identical to fflush except that it is not protected from interference by other threads. It might be faster because it does not incur the overhead of locking out other threads. Use this function only in thread-safe contexts such as single-threaded applications or where the calling scope already handles thread isolation.
For more compatibility information, see Compatibility in the Introduction.