C difftime() function

C difftime() function - Compute the difference between two calendar time values

The difftime() function is used to compute the difference in seconds between two times.

Syntax:

double difftime(time_t time1, time_t time2)

Parameters:

Return value from difftime()

• The ctime() function returns a pointer to the character string result.
• If the function is unsuccessful, it returns NULL. 

Example: difftime() function

The following example shows the usage of difftime() function.

#include <time.h>
#include <stdio.h>
#include <unistd.h>
#define SIZE 10
 
int mark[SIZE];
 
int main(void)
{
   time_t start, finish;
   int n, even_num=0, odd_num=0;
 
   time(&start);
 
   /*  This loop finds the even and odd numbers between 1 and SIZE   */
      for (n = 1; n <= SIZE; n++)
      {
	   if(n%2 == 0) 
         {
            even_num++;
            }
        else
         odd_num++;
         printf("n = %d\n",n);
         sleep(1);
      }
   time(&finish);
   printf("Program takes an average of %f seconds "
                  "to find %d even numbers and %d odd numbers.\n",
                   difftime(finish,start)/n, even_num, odd_num);
}

Output:

n = 1
n = 2
n = 3
n = 4
n = 5
n = 6
n = 7
n = 8
n = 9
n = 10
Program takes an average of 0.909091 seconds to find 5 even numbers and 5 odd numbers.

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