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Document TIMEVAL_TO_TIMESPEC() and TIMESPEC_TO_TIMEVAL().

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.Dd $Mdocdate: May 10 2019 $
.Dt TIMERADD 3
.Os
.Sh NAME
.Nm timerclear ,
.Nm timerisset ,
.Nm timerisvalid ,
.Nm timercmp ,
.Nm timersub ,
.Nm timeradd ,
.Nm timespecclear ,
.Nm timespecisset ,
.Nm timespecisvalid ,
.Nm timespeccmp ,
.Nm timespecsub ,
.Nm timespecadd ,
.Nm TIMEVAL_TO_TIMESPEC ,
.Nm TIMESPEC_TO_TIMEVAL
.Nd manipulate time structures
.Sh SYNOPSIS
.In sys/time.h
.Ft void
.Fn timerclear "struct timeval *a"
.Ft int
.Fn timerisset "struct timeval *a"
.Ft int
.Fn timerisvalid "struct timeval *a"
.Ft int
.Fn timercmp "struct timeval *a" "struct timeval *b" operator
.Ft void
.Fn timersub "struct timeval *a" "struct timeval *b" "struct timeval *c"
.Ft void
.Fn timeradd "struct timeval *a" "struct timeval *b" "struct timeval *c"
.Ft void
.Fn timespecclear "struct timespec *a"
.Ft int
.Fn timespecisset "struct timespec *a"
.Ft int
.Fn timespecisvalid "struct timespec *a"
.Ft int
.Fn timespeccmp "struct timespec *a" "struct timespec *b" operator
.Ft void
.Fn timespecsub "struct timespec *a" "struct timespec *b" "struct timespec *c"
.Ft void
.Fn timespecadd "struct timespec *a" "struct timespec *b" "struct timespec *c"
.Ft void
.Fn TIMEVAL_TO_TIMESPEC "struct timeval *tv" "struct timespec *ts"
.Ft void
.Fn TIMESPEC_TO_TIMEVAL "struct timeval *tv" "struct timespec *ts"
.Sh DESCRIPTION
The
.Fn timer*
and
.Fn timespec*
macros defined in
.In sys/time.h
simplify the use of
.Vt timeval
and
.Vt timespec
structures,
respectively.
.Pp
The following macros are available:
.Bl -tag -width Ds
.It Fn timerclear a , Fn timespecclear a
Set the time value in
.Fa a
to zero.
.It Fn timerisset a , Fn timespecisset a
Test if the time value in
.Fa a
is non-zero.
.It Fn timerisvalid a
Test if the microsecond value in
.Fa a
is greater than or equal to zero and less than one million.
.It Fn timespecisvalid a
Test if the nanosecond value in
.Fa a
is greater than or equal to zero and less than one billion.
.It Fn timercmp a b operator , Fn timespeccmp a b operator
Test if the expression
.Fa a operator b
is true,
where
.Fa operator
is one of
.Cm < ,
.Cm <= ,
.Cm == ,
.Cm != ,
.Cm >= ,
or
.Cm > .
.It Fn timersub a b c , Fn timespecsub a b c
Subtract
.Fa b
from
.Fa a
and store the result in
.Fa c .
.It Fn timeradd a b c , Fn timespecadd a b c
Add
.Fa b
to
.Fa a
and store the result in
.Fa c .
.It Fn TIMEVAL_TO_TIMESPEC tv ts
Convert
.Fa tv
to a
.Vt struct timespec
and store the result in
.Fa ts .
.It Fn TIMESPEC_TO_TIMEVAL tv ts
Convert
.Fa ts
to a
.Vt struct timeval
and store the result in
.Fa tv .
.El
.Sh RETURN VALUES
The macros returning
.Vt int
return 1 if the tested condition holds or 0 otherwise.
.Sh SEE ALSO
.Xr adjtime 2 ,
.Xr clock_gettime 2 ,
.Xr futex 2 ,
.Xr futimens 2 ,
.Xr futimes 2 ,
.Xr getitimer 2 ,
.Xr gettimeofday 2 ,
.Xr kevent 2 ,
.Xr nanosleep 2 ,
.Xr ppoll 2 ,
.Xr pselect 2
.Sh STANDARDS
These macros are non-standard,
though many systems offer them.
Similar interfaces are often available in their absence.
.Sh HISTORY
The macros
.Fn timerclear ,
.Fn timerisset ,
and
.Fn timercmp
first appeared in
.Bx 4.1c ,
.Fn TIMEVAL_TO_TIMESPEC
and
.Fn TIMESPEC_TO_TIMEVAL
in
.Bx 4.4 ,
.Fn timersub
and
.Fn timeradd
in
.Nx 1.1 ,
and
.Fn timerisvalid
in
.Ox 6.5 .
.Sh CAVEATS
The argument ordering for
.Fn TIMESPEC_TO_TIMEVAL
is unintuitive.