NAME

       timeval, timespec — time structures

LIBRARY

       Utility functions from BSD systems (libbsd, -lbsd)

SYNOPSIS

       #include <sys/time.h>
       (See libbsd(7) for include usage.)

       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 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.

EXAMPLES

       It  can  be  stressed  that  the traditional UNIX timeval and timespec structures represent elapsed time,
       measured by the system clock.  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(3bsd)

Debian                                           April 12, 2011                                    timeval(3bsd)