timerisset

       tions

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 time at midnight on the morning  of  1  January  1970
       (the Epoch).

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

       timercmp() compares the timer values in a and b  using  the  comparison
       operator CMP, and returns true (non-zero) 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(..., !=)

COLOPHON
       This page is part of release 3.23 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



Linux                             2009-02-26                       TIMERADD(3)