C sleep function not working

Question

When including the sleep function from unistd.h the program hangs indefinitely:

#include 
#include 

int main()
{         


        

Answer 1

hangs indefinitely implies that it's stuck or non-deterministic, and that doesn't happen. Your code works fine, after 38 seconds (19 *2) it dumps the string counting from 0 to 19. However I suspect this is what you were looking for it to do:

int main()
{
        int i;
        printf("0 ");
        fflush(stdout);  // Force the output to be printed
        for(i = 1; i <20; ++i)
        {
            sleep(2);
            printf("%d ", i);
            fflush(stdout); // Force the output to be printed
        }
        printf("\n");

        return 0;
}

the stdout stream is buffered and is only going to display when it hits a newline '\n' or if you want to view it "real time" as your call printf() you need to force it to flush the buffer one way or another. A call to fflush(stdout) will do this.