#define _POSIX_C_SOURCE 199309L
#include <stdio.h>
#include <time.h>

int main(int argc,char* argv[])
{
  time_t now;
  time(&now);
  printf("Today is: %s", ctime(&now));

  for (int i = 0; i < 40; i++) {
    if (i % 7 == 0) {
      fprintf(stderr, "ERROR: process(%s): %d\n", argv[1], i);
    } else {
      fprintf(stdout, "process(%s):%d\n", argv[1], i);
    }
    // sleep for 1/10 second
    nanosleep((const struct timespec[]){{0, 100000000L}}, NULL);
  }

  time_t end;
  time(&end);
  printf("Elapsed time is: %2.3fs\n", difftime(end, now));
  printf("Elapsed time is: %2.3fs\n", (double)(end - now));
  return 0;
}