POSIX C/C++ sleep() and usleep() not working? (Raspberry PI)

Question

I wrote a small programm on my RasPI and have trouble with the sleep() and usleep() functions. both of them don't work. When I use usleep() with a number below 1000000 (below 1 second) it works, whenever i try to use a number that should let the program sleep for 1 second or more, it doesn't work. I've been working on making the Digital pin HIGH for a given time.

I've tried to shrink the program to printf() and to sleep only:

#include <stdio.h>
#include <unistd.h>

int main()
{

    while (true)
    {
        sleep(1);
        printf("%.2f", 10.1);
    }
}

Answer 1

works after flushing the output buffer

#include <stdio.h>
#include <unistd.h>
#include <chrono>
#include <thread>


int main()
{

    while (true)
    {
        std::this_thread::sleep_for(std::chrono::seconds(1));
        printf("%.2f\n", 10.1);
    }
}