Streams in C1 are thread-safe2. Functions are required to lock the stream before accessing it3. The fflush function is thread-safe and may be called from any thread at any time, as long as the stream is an output stream or an update stream4. 1 As per the current standard, which is C11. 2 (Quoted from: … Read more
fflush() works on FILE*, it just flushes the internal buffers in the FILE* of your application out to the OS. fsync works on a lower level, it tells the OS to flush its buffers to the physical media. OSs heavily cache data you write to a file. If the OS enforced every write to hit … Read more
Flushing the output buffers: printf(“Buffered, will be flushed”); fflush(stdout); // Prints to screen or whatever your standard out is or fprintf(fd, “Buffered, will be flushed”); fflush(fd); //Prints to a file Can be a very helpful technique. Why would you want to flush an output buffer? Usually when I do it, it’s because the code is … Read more
Simple: this is undefined behavior, since fflush is meant to be called on an output stream. This is an excerpt from the C standard: int fflush(FILE *ostream); ostream points to an output stream or an update stream in which the most recent operation was not input, the fflush function causes any unwritten data for that … Read more