.\" Copyright (c) 1999 Kelly Yancey <kbyanc@posi.net>
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.\" $FreeBSD$
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.Dd July 30, 2018
.Dt TIMERADD 3
.Os
.Sh NAME
.Nm timeradd ,
.Nm timersub ,
.Nm timerclear ,
.Nm timerisset ,
.Nm timercmp ,
.Nm timespecadd ,
.Nm timespecsub ,
.Nm timespecclear ,
.Nm timespecisset ,
.Nm timespeccmp
.Nd operations on timevals and timespecs
.Sh SYNOPSIS
.In sys/time.h
.Ft void
.Fn timeradd "struct timeval *a" "struct timeval *b" "struct timeval *res"
.Ft void
.Fn timersub "struct timeval *a" "struct timeval *b" "struct timeval *res"
.Ft void
.Fn timerclear "struct timeval *tvp"
.Ft int
.Fn timerisset "struct timeval *tvp"
.Ft int
.Fn timercmp "struct timeval *a" "struct timeval *b" CMP
.Ft void
.Fn timespecadd "struct timespec *a" "struct timespec *b" "struct timespec *res"
.Ft void
.Fn timespecsub "struct timespec *a" "struct timespec *b" "struct timespec *res"
.Ft void
.Fn timespecclear "struct timespec *ts"
.Ft int
.Fn timespecisset "struct timespec *ts"
.Ft int
.Fn timespeccmp "struct timespec *a" "struct timespec *b" CMP
.Sh DESCRIPTION
These macros are provided for manipulating
.Fa timeval
and
.Fa timespec
structures for use with the
.Xr clock_gettime 2 ,
.Xr clock_settime 2 ,
.Xr gettimeofday 2
and
.Xr settimeofday 2
calls.
The
.Fa timeval
structure is defined in
.In sys/time.h
as:
.Bd -literal
struct timeval {
	long	tv_sec;		/* seconds since Jan. 1, 1970 */
	long	tv_usec;	/* and microseconds */
};
.Ed
And the
.Fa timespec
structure is defined in
.In time.h
as:
.Bd -literal
struct timespec {
	time_t tv_sec;		/* seconds */
	long   tv_nsec;		/* and nanoseconds */
};
.Ed
.Pp
.Fn timeradd
and
.Fn timespecadd
add the time information stored in
.Fa a
to
.Fa b
and store the result in
.Fa res .
The results are simplified such that the value of
.Fa res->tv_usec
or
.Fa res->tv_nsec
is always less than 1 second.
.Pp
.Fn timersub
and
.Fn timespecsub
subtract the time information stored in
.Fa b
from
.Fa a
and store the result
in
.Fa res .
.Pp
.Fn timerclear
and
.Fn timespecclear
initialize their argument to midnight (0 hour) January 1st, 1970 (the Epoch).
.Pp
.Fn timerisset
and
.Fn timespecisset
return true if their argument is set to any time value other than the Epoch.
.Pp
.Fn timercmp
and
.Fn timespeccmp
compare
.Fa a
to
.Fa b
using the comparison operator given in
.Fa CMP ,
and return the result of that comparison.
.Sh SEE ALSO
.Xr gettimeofday 2 ,
.Xr clock_gettime 2
.Sh HISTORY
The
.Fn timeradd
family of macros were imported from
.Nx 1.1 ,
and appeared in
.Fx 2.2.6 .
The
.Fn timespecadd
family of macros were imported from
.Nx 1.3
into
.Fx 3.0 ,
though they were not exposed to userland until
.Fx 12.0 .