timerisset (3)
Leading comments
Copyright (c) 2007 by Michael Kerrisk <mtk.manpages@gmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this on...
NAME
timeradd, timersub, timercmp, timerclear, timerisset - timeval operationsSYNOPSIS
#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(..., !=)