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itimerval(3) [netbsd man page]

TIMEVAL(3)						   BSD Library Functions Manual 						TIMEVAL(3)

timeval, timespec, itimerval, itimerspec, bintime -- time structures SYNOPSIS
#include <sys/time.h> void TIMEVAL_TO_TIMESPEC(struct timeval *tv, struct timespec *ts); void TIMESPEC_TO_TIMEVAL(struct timeval *tv, struct timespec *ts); DESCRIPTION
The <sys/time.h> header, included by <time.h>, defines various structures related to time and timers. 1. The following structure is used by gettimeofday(2), among others: 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. 2. The following structure is used by nanosleep(2), among others: 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 nanosec- onds. 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. 3. The following structure is used by setitimer(2), among others: struct itimerval { struct timeval it_interval; struct timeval it_value; }; 4. The following structure is used by timer_settime(2), among others: 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. 5. The following structure is used by bintime(9), among others: 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). EXAMPLES
It can be stressed that the traditional UNIX timeval and timespec structures represent elapsed time, measured by the system clock (see hz(9)). The following sketch implements a function suitable for use in a context where the timespec structure is required for a conditional timeout: 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). SEE ALSO
timeradd(3), tm(3), bintime_add(9) BSD
April 12, 2011 BSD

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TIMERADD(3)						   BSD Library Functions Manual 					       TIMERADD(3)

timeradd -- operations on time structure SYNOPSIS
#include <sys/time.h> void timeradd(struct timeval *a, struct timeval *b, struct timeval *res); void timersub(struct timeval *a, struct timeval *b, struct timeval *res); void timerclear(struct timeval *tv); int timerisset(struct timeval *tv); int timercmp(struct timeval *a, struct timeval *b, CMP); void timespecadd(struct timespec *a, struct timespec *b, struct timespec *res); void timespecsub(struct timespec *a, struct timespec *b, struct timespec *res); void timespecclear(struct timespec *ts); int timespecisset(struct timespec *ts); int timespeccmp(struct timespec *a, struct timespec b, CMP); DESCRIPTION
These macros are provided for manipulating the timeval and timespec structures described in timeval(3). The timeradd() and timespecadd() macros add the time information stored in a to b, storing the result in res. With timeradd() the results are simplified such that the value of res->tv_usec is always less than 1,000,000 (1 second). With timespecadd() the res->tv_nsec member of struct timespec is always less than 1,000,000,000. The timersub() and timespecsub() macros subtract the time information stored in b from a and store the resulting structure in res. The timerclear() and timespecclear() macros initialize the structures to midnight (0 hour) January 1st, 1970 (the Epoch). In other words, they set the members of the structure to zero. The timerisset() and timespecisset() macros return true if the input structure is set to any time value other than the Epoch. The timercmp() and timespeccmp() macros compare a to b using the comparison operator given in CMP. The result of the comparison is returned. SEE ALSO
timeval(3) HISTORY
The timeradd() family of macros first appeared in NetBSD 1.1. These were later ported to FreeBSD 2.2.6. The timespec() family of macros first appeared in NetBSD 1.2. BSD
June 7, 2010 BSD
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