63885319.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

static uint64_t usecdiff(struct timeval *a, struct timeval *b) {
  uint64_t sec_diff = b->tv_sec - a->tv_sec;
  uint64_t usec_diff = b->tv_usec - a->tv_usec;
  return sec_diff * 1000000 + usec_diff;
}

int main() {
  struct timeval start, curr;
  gettimeofday(&start, NULL);
  for (;;) {
    gettimeofday(&curr, NULL);
    uint64_t diff = usecdiff(&start, &curr);
    start = curr;
    printf("%llu\n", diff);
    usleep(1000000);
  }
}