timersub

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 nor-
       malized 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).
       description of the project, information about reporting bugs,  and  the
       latest     version     of     this    page,    can    be    found    at
       http://www.kernel.org/doc/man-pages/.

Linux                             2010-02-25                       TIMERADD(3)
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