Will an ostream flush other stream?

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I'm curious about why I output by different ostream, and don't flush them, but when program exited, they won't mess up the order, does an ostream flush others stream?how C++ standard library make they communicate?

#include <iostream>

int main()
{
    std::clog << "flush test1 by clog\n";
    std::cout << "flush test1 by cout\n";
    std::cout << "flush test2 by cout\n";
    std::clog << "flush test2 by clog\n";
    return 0;
}

/* The output is
 * flush test1 by clog
 * flush test1 by cout
 * flush test2 by cout
 * flush test2 by clog
 */
visual-c++ c++
1 Answers

The clog stream is usually the same as the cerr stream, which is, depending on your library either line-buffer or not buffered meaning that at least after a line break (\n) it is written onto your terminal. cout on the other hand might be either fully buffered (only written if the buffer is full or flushed), line-buffered or not buffered. Even more specific from cplusplus.com: ("If stdout is known to not refer to an interactive device, the stream is fully buffered. Otherwise, it is library-dependent whether the stream is line buffered or not buffered by default."). Assuming your terminal is interactive, the cout buffer is written to your termial at least after every line.

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