.\"	$NetBSD: timer_settime.2,v 1.10 2021/09/23 13:49:59 uwe Exp $
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.Dd May 17, 2010
.Dt TIMER_SETTIME 2
.Os
.Sh NAME
.Nm timer_settime ,
.Nm timer_gettime ,
.Nm timer_getoverrun
.Nd process timer manipulation
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In time.h
.Ft int
.Fn timer_settime "timer_t timerid" "int flags" "const struct itimerspec * restrict tim" "struct itimerspec * restrict otim"
.Ft int
.Fn timer_gettime "timer_t timerid" "struct itimerspec *tim"
.Ft int
.Fn timer_getoverrun "timer_t timerid"
.Sh DESCRIPTION
The
.Fn timer_settime
sets the next expiration time of the timer with ID
.Ar timerid
to the
.Fa it_value
(see
.Xr itimerspec 3 )
specified in the
.Ar tim
argument.
If the value is 0, the timer is disarmed.
If the argument
.Ar otim
is not
.Dv NULL
the old timer settings are returned.
.Pp
If the
.Ar flags
argument is set to
.Dv TIMER_RELTIME
then the expiration time is set to the value in nanoseconds specified
in the
.Ar tim
argument from the time the call to
.Fn timer_settime
was made.
If the
.Ar flags
argument is set to
.Dv TIMER_ABSTIME
then the expiration time is set to be equal to the difference between the
clock associated with this timer, and the value specified in the
.Ar tim
argument.
If that time has already passed, then the call succeeds, and the
expiration notification occurs.
.Pp
If the
.Fa it_interval
of the
.Ar tim
argument is non-zero, then the timer reloads upon expiration.
.Pp
The
.Fn timer_gettime
function returns the current settings of the timer
specified by the
.Ar timerid
argument in the
.Ar tim
argument.
.Pp
Only one notification event (signal) can be pending for a given timer
and process.
If a timer expires while the signal is still queued for delivery, then
the overrun counter for that timer is increased.
The counter can store values up to
.Dv DELAYTIMER_MAX .
When the signal is finally delivered to the process, then the
.Fn timer_getoverrun
function can be used to retrieve the overrun counter for the timer
specified in the
.Ar timerid
argument.
.Sh NOTES
Expiration time values are always rounded up to the resolution of the timer,
so a notification will never be sent before the requested time.
Values returned in the
.Ar otim
argument of
.Fn timer_settime
or in the
.Ar tim
argument of
.Fn timer_gettime
are subject to the above rounding effect and might not exactly match the
requested values by the user.
.Sh RETURN VALUES
If successful, the
.Fn timer_gettime
and
.Fn timer_settime
functions return 0, and the
.Fn timer_getoverrun
function returns the expiration overrun count for the specified timer.
Otherwise, the functions return \-1, and set
.Dv errno
to indicate the error.
.Sh ERRORS
The
.Fn timer_gettime ,
.Fn timer_getoverrun ,
and
.Fn timer_settime
functions will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
The argument
.Ar timerid
does not correspond to a valid timer id as returned by
.Fn timer_create
or that timer id has been deleted by
.Fn timer_delete .
.El
.Pp
The
.Fn timer_settime
function will fail if:
.Bl -tag -width Er
.It Bq Er EINVAL
A nanosecond field in the
.Ar tim
structure specified a value less than zero or greater than or equal
to\~10^9.
.El
.Sh SEE ALSO
.Xr clock_gettime 2 ,
.Xr timer_create 2 ,
.Xr timer_delete 2
.Sh STANDARDS
.St -p1003.1b-93 ,
.St -p1003.1i-95
.\"  LocalWords:  gettime settime