Question

How can I know the seconds and microseconds between 1 January 1970 00:00:00 and now using timeval? Thanks.

struct timeval {
  long tv_sec; /*seconds since 1/1/1970*/
  long tv_usec; /*microseconds since tv_sec*/
};

Answer 1

you call gettimeofday()

struct timeval tv;
gettimeofday(&tv, NULL);
tv.tv_sec  /* seconds */
tv.tv_usec /* microseconds */

However gettimeofday() is obsolete, the manual is recommending clock_gettime(2) instead:

struct timespec tp;
clock_gettime(CLOCK_REALTIME, &tp);
tp.tv_sec  /* seconds */
tp.tv_usec /* nanoseconds divide by 1000 to get microseconds*/