| TIMEVAL(3) | Library Functions Manual | TIMEVAL(3) |
timeval, timespec,
itimerval, itimerspec,
bintime —
#include <sys/time.h>
void
TIMEVAL_TO_TIMESPEC(struct
timeval *tv, struct
timespec *ts);
void
TIMESPEC_TO_TIMEVAL(struct
timeval *tv, struct
timespec *ts);
<sys/time.h> header,
included by <time.h>, defines
various structures related to time and timers.
struct timeval {
time_t tv_sec;
suseconds_t tv_usec;
};
The tv_sec member represents the elapsed time, in whole seconds. The tv_usec member captures rest of the elapsed time, represented as the number of microseconds.
struct timespec {
time_t tv_sec;
long tv_nsec;
};
The tv_sec member is again the elapsed time in whole seconds. The tv_nsec member represents the rest of the elapsed time in nanoseconds.
A microsecond is equal to one millionth of a second, 1000
nanoseconds, or 1/1000 milliseconds. To ease the conversions, the macros
TIMEVAL_TO_TIMESPEC() and
TIMESPEC_TO_TIMEVAL() can be used to convert
between struct timeval and struct
timespec.
struct itimerval {
struct timeval it_interval;
struct timeval it_value;
};
struct itimerspec {
struct timespec it_interval;
struct timespec it_value;
};
Both struct itimerval and struct itimerspec are used to specify when a timer expires. Generally, it_interval specifies the period between successive timer expirations. A value zero implies that the alarm will fire only once. If it_value is non-zero, it indicates the time left to the next timer expiration. A value zero implies that the timer is disabled.
struct bintime {
time_t sec;
uint64_t frac;
};
The sec member specifies the time in seconds and frac represents a 64-bit fraction of seconds. The struct bintime is meant to be used in the kernel only. It is further described in timecounter(9).
static void
example(struct timespec *spec, time_t minutes)
{
struct timeval elapsed;
(void)gettimeofday(&elapsed, NULL);
_DIAGASSERT(spec != NULL);
TIMEVAL_TO_TIMESPEC(&elapsed, spec);
/* Add the offset for timeout in minutes. */
spec->tv_sec = spec->tv_sec + minutes * 60;
}
A better alternative would use the more precise clock_gettime(2).
| April 12, 2011 | NetBSD 10.1 |