TIMERADD(3)						     Linux Programmer's Manual						       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: _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

       This  page is part of release 3.27 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								    2010-02-25							       TIMERADD(3)