TIMERADD(3)            FreeBSD Library Functions Manual            TIMERADD(3)

NAME
     timeradd, timersub, timerclear, timerisset, timercmp, timespecadd,
     timespecsub, timespecclear, timespecisset, timespeccmp - operations on
     timevals and timespecs

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 *tvp);

     int
     timerisset(struct timeval *tvp);

     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 timeval and timespec
     structures for use with the clock_gettime(2), clock_settime(2),
     gettimeofday(2) and settimeofday(2) calls.  The timeval structure is
     defined in <sys/time.h> as:

     struct timeval {
             long    tv_sec;         /* seconds since Jan. 1, 1970 */
             long    tv_usec;        /* and microseconds */
     };
     And the timespec structure is defined in <time.h> as:

     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.

SEE ALSO
     clock_gettime(2), gettimeofday(2)

HISTORY
     The timeradd() family of macros were imported from NetBSD 1.1, and
     appeared in FreeBSD 2.2.6.  The timespecadd() family of macros were
     imported from NetBSD 1.3 into FreeBSD 3.0, though they were not exposed
     to userland until FreeBSD 12.0.

FreeBSD 13.1-RELEASE-p6          July 30, 2018         FreeBSD 13.1-RELEASE-p6