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timeradd(3)


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:
       Since glibc 2.19:
           _DEFAULT_SOURCE
       Glibc 2.19 and earlier:
           _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.  Present on most BSD derivatives.

SEE ALSO

   gettimeofday(2), time(7)

COLOPHON

   This page is part of release 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at
   https://www.kernel.org/doc/man-pages/.



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