c - What is the proper #include for the function 'sleep()'?

Question

I am using the Big Nerd Ranch book Objective-C Programming, and it starts out by having us write in C in the first few chapters. In one of my programs it has me create, I use the sleep function. In the book it told me to put #include <stdlib.h> under the #include <stdio.h> part. This is supposed to get rid of the warning that says "Implicit declaration of function 'sleep' is invalid in C99". But for some reason after I put #include <stdlib.h>, the warning does not go away.. This problem does not stop the program from running fine, but I was just curious on which #include I needed to use!

Answer 1

The sleep man page says it is declared in <unistd.h>.

Synopsis:

#include <unistd.h>

unsigned int sleep(unsigned int seconds);