timer_gettime() places in itimerspec the amount of time until timer, timerid, expires (in itimerspec.it_value) and the reload value of the timer (in itimerspec.it_interval). itimerspec.it_value contains 0 if the timer was disarmed. itimerspec.it_value returns a relative time amount, even if the timer was absolute. timer_gettime() returns 0 on success timer_gettime() returns -1 on failure If timer ID does not correspond to a valid timer ID (i.e., one created using timer_create() but not yet deleted with timer_delete()), timer_gettime() may return errno==EINVAL.