1 #include <stdio.h>
   2 #include <time.h>
   3 #include <stdlib.h>
   4 #include <unistd.h>
   5 #include <errno.h>
   6 
   7 #define MAX_PRIME 10000000
   8 
   9 int main(int argc, char ** argv)
  10 {
  11   int seconds = 5;
  12   time_t start, end, run_time, end1, run_time1;
  13   unsigned long i, num, primes = 0;
  14   start = time(NULL);
  15   printf("%u\n", 1);
  16   for (num = 1; num <= MAX_PRIME; ++num)
  17   {
  18     for (i = 2; (i <= num) && (num % i != 0); ++i);
  19     if (i == num)
  20     {
  21       ++primes;
  22       printf("%u\n", i);
  23     }
  24     end1 = time(NULL);
  25     run_time1 = (end1 - start);
  26     if ( run_time1 >= seconds ) break;
  27   }
  28   end = time(NULL);
  29   run_time = (end - start);
  30   printf("This program calculated %d prime numbers under %d "
  31            "in %d seconds\n", primes, num, run_time);
  32 }