.\"	$OpenBSD: nanosleep.2,v 1.18 2021/07/25 15:47:26 cheloha Exp $
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.\"     @(#)sleep.3	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: July 25 2021 $
.Dt NANOSLEEP 2
.Os
.Sh NAME
.Nm nanosleep
.Nd high resolution sleep
.Sh SYNOPSIS
.In time.h
.Ft int
.Fn nanosleep "const struct timespec *timeout" "struct timespec *remainder"
.Sh DESCRIPTION
The
.Fn nanosleep
function suspends execution of the calling thread for at least the given
.Fa timeout .
Delivery of an unmasked signal terminates this sleep early,
even if
.Dv SA_RESTART
is set with
.Xr sigaction 2
for the interrupting signal.
.Sh RETURN VALUES
If
.Fn nanosleep
sleeps the full
.Fa timeout
without interruption it returns 0.
Unless
.Fa remainder
is
.Dv NULL ,
it is set to zero.
.Pp
If
.Fn nanosleep
is interrupted by a signal it returns \-1 and the global variable
.Va errno
is set to
.Dv EINTR .
Unless
.Fa remainder
is
.Dv NULL ,
it is set to the unslept portion of the
.Fa timeout .
.Pp
Otherwise,
.Fn nanosleep
returns \-1 and the global variable
.Va errno
is set to indicate the error.
.Sh ERRORS
.Fn nanosleep
will fail if:
.Bl -tag -width Er
.It Bq Er EINTR
The call is interrupted by the delivery of a signal.
.It Bq Er EINVAL
.Fa timeout
specifies a nanosecond value less than zero or greater than or equal to
one billion,
or a second value less than zero.
.It Bq Er EFAULT
.Fa timeout
points to memory that is not a valid part of the process address space.
.It Bq Er EFAULT
.Fa remainder
is not
.Dv NULL
and points to memory that is not a valid part of the process address space.
.El
.Sh SEE ALSO
.Xr sleep 1 ,
.Xr sigaction 2 ,
.Xr sleep 3
.Sh STANDARDS
The
.Fn nanosleep
function conforms to
.St -p1003.1-2008 .
.Sh HISTORY
The predecessor of this system call,
.Fn sleep ,
first appeared in
.At v2 .
It was removed in
.At v7
and replaced with a C library implementation based on
.Xr alarm 3
and
.Xr signal 3 .
.Pp
The
.Fn nanosleep
function first appeared in
.St -p1003.1b-93 .
.Pp
This implementation of
.Fn nanosleep
first appeared in
.Nx 1.3
and was ported to
.Ox 2.1 .