exercise04.c

// C Primer Plus
// Chapter 16 Exercise 4:

// The ANSI library features a clock() function with this description:
// 	 #include <time.h> clock_t clock (void);
// Here, clock_t is a type defined in time.h. The function returns the
// processor time, which is given in some implementation-dependent units. (If
// the processor time is unavailable or cannot be represented, the function
// returns a value of -1.) However, CLOCKS_PER_SEC, also defined in time.h, is
// the number of processor time units per second. Therefore, dividing the
// difference between two return values of clock() by CLOCKS_PER_SEC gives you
// the number of seconds elapsed between the two calls. Typecasting the values
// to double before division enables you to get fractions of a second. Write a
// function that takes a double argument representing a desired time delay and
// then runs a loop until that amount of time has passed. Write a simple
// program that tests the function.

#include <stdio.h>
#include <time.h>

void timeout(double time);

int main(void)
{
	double time;

	printf("Enter desired time delay in seconds: ");
	while(scanf("%lf", &time) == 1)
	{
		puts("Starting.");
		timeout(time);
		printf("It is now %2f seconds later!\n", time);
		printf("Enter desired time delay in seconds: ");
	}
	puts("Bye.");
}

void timeout(double time)
{
	clock_t start, end;

	start = clock();

	while (((end = clock()) - start) /  (double) CLOCKS_PER_SEC < time)
		continue;

	return;
}