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NAME

       timeradd,   timersub,   timercmp,   timerclear,  timerisset  -  timeval
       operations

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);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       All functions shown above: _BSD_SOURCE

DESCRIPTION

       The macros are provided to operate on timeval  structures,  defined  in
       <sys/time.h> as:

           struct timeval {
               time_t      tv_sec;     /* seconds */
               suseconds_t tv_usec;    /* microseconds */
           };

       timeradd()  adds  the time values in a and b, and places the sum in the
       timeval pointed  to  by  res.   The  result  is  normalized  such  that
       res->tv_usec has a value in the range 0 to 999,999.

       timersub()  subtracts the time value in b from the time value in a, and
       places the result in the timeval pointed to  by  res.   The  result  is
       normalized  such  that  res->tv_usec  has  a  value  in  the range 0 to
       999,999.

       timerclear() zeros out the timeval structure pointed to by tvp, so that
       it represents the Epoch: 1970-01-01 00:00:00 +0000 (UTC).

       timerisset()  returns  true  (nonzero)  if  either field of the timeval
       structure pointed to by tvp contains a nonzero value.

       timercmp() compares the timer values in a and b  using  the  comparison
       operator  CMP, and returns true (nonzero) or false (0) depending on the
       result of the comparison.  Some systems (but not Linux/glibc),  have  a
       broken timercmp() implementation, in which CMP of >=, <=, and == do not
       work; portable applications can instead use

           !timercmp(..., <)
           !timercmp(..., >)
           !timercmp(..., !=)

RETURN VALUE

       timerisset() and timercmp() return true (nonzero) or false (0).

ERRORS

       No errors are defined.

CONFORMING TO

       Not in POSIX.1-2001.  Present on most BSD derivatives.

SEE ALSO

       gettimeofday(2), time(7)

COLOPHON

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