The consequences and pros/cons of flushing the stream in c++

Question

I have recently read an article which stated that using \\n is preferable to using std::endl because endl also flushes the stream.

Answer 1

I hope you've lost the link to that site that you found. std::endl does not avoid buffering. It flushes whatever is in the buffer. If you need to avoid buffering, use setf(ios_base::unitbuf). That sets the stream to flush after each insertion. That's the default setting for std::clog. The reason for doing this is that the less stuff being held in the buffer, the greater the chance that critical data will have been written to the stream when the program crashes.

Flushing also matters for interactive programs: if you write a prompt to std::cout, it's a Good Thing if that prompt shows up on the display before the program starts waiting for input. That's done automatically when you use std::cout and std::cin, unless you've messed with the synchronization settings.

Many programmers seem to use std::endl as a fancy way of spelling '\n', but it's not. You don't need to flush the output buffer every time you write something to it. Let the OS and the standard library do their jobs; they'll take care of getting the output to the appropriate place in a timely manner. A simple std::cout << '\n'; is all that's needed to put a newline into the output, and sooner or later, that will show up on the display. If you need to have it show now, typically because you've written all of the output for the time being and don't want to leave the displayed information incomplete, use std::endl after the last line of the output.