escape sequences

[cfanatic]

Hi all.

I am trying to play a sound 5 times. If I remove the \n in printf(), the sound plays only once. What is the relationship between the \n and the \a that would cause this behaviour? The printf()'s are seperate statements, so I don't see the correlation.

Thanks.

#include <stdio.h>

int main(void)
{
    int count;

    for(count = 0; count < 5; count++)
    {
        int count;

        for(count = 0; count < 95000000; count++)
        {
            ;
        }

        printf("hello\n");
        printf("\a");
    }

    return 0;
}

[smokeyangel]

That's surprising to me! What compiler are you using?

The only thing I can think of is output buffering. If all the output is buffered, then output in a big chunk at the end then it would probably just sound like a single beep.

This page for GCC Flushing Buffers - The GNU C Library says that newlines flush the buffer, so it could be that but I'm really not very convinced. You could try to confirm this by taking the \n out and calling fflush(stdout) after the print of \a.

[grumpy]

It's not surprising at all.

stdout is buffered. A '\n' character causes stdout's buffer to be flushed.

Using fflush(stdout) would also flush stdout, without having to output a '\n'. You would also find that fprintf(stderr, ....) will do what you want, without any flushing, since stderr is not buffered.

Also, be careful of your inner loop. There is nothing stopping a compiler from eliding it (i.e. removing it completely) since a compiler can detect it has no effect on observable output (except timings). Depending on operating system, you would be better off using a function such as sleep() [Most unix variants] or Sleep() [Windows].