how to sleep in c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
 
int main(){
  
	printf("Sleeping for 5 seconds \n");
	sleep(5);
	printf("Sleep is now over \n");  
}

void sleep(unsigned int mseconds)
{
    clock_t goal = mseconds + clock();
    while (goal > clock())
        ;
}

void sleep(unsigned int mseconds)
{
    clock_t goal = mseconds + clock();
    while (goal > clock())
        ;
}

#ifdef __unix__
# include <unistd.h>
#elif defined _WIN32
# include <windows.h>
#define sleep(x) Sleep(1000 * (x))
#endif