Manual Pages  — TIMERADD

struct timeval {
        long    tv_sec;         /* seconds since Jan. 1, 1970 */
        long    tv_usec;        /* and microseconds */
};

struct timespec {
        time_t tv_sec;          /* seconds */
        long   tv_nsec;         /* and nanoseconds */
};

timeradd() and timespecadd() add the time information stored in a to b and store the result in res. The results are simplified such that the value of res->tv_usec or res->tv_nsec is always less than 1 second.

timersub() and timespecsub() subtract the time information stored in b from a and store the result in res.

timerclear() and timespecclear() initialize their argument to midnight (0 hour) January 1st, 1970 (the Epoch).

timerisset() and timespecisset() return true if their argument is set to any time value other than the Epoch.

timercmp() and timespeccmp() compare a to b using the comparison operator given in CMP, and return the result of that comparison.