.\"	$OpenBSD: nanosleep.2,v 1.14 2013/07/17 05:42:11 schwarze Exp $
.\"	$NetBSD: nanosleep.2,v 1.1 1997/04/17 18:12:02 jtc Exp $
.\"
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.\"     @(#)sleep.3	8.1 (Berkeley) 6/4/93
.\"
.Dd $Mdocdate: July 17 2013 $
.Dt NANOSLEEP 2
.Os
.Sh NAME
.Nm nanosleep
.Nd high resolution sleep
.Sh SYNOPSIS
.Fd #include <time.h>
.Ft int
.Fn nanosleep "const struct timespec *timeout" "struct timespec *remainder"
.Sh DESCRIPTION
.Fn nanosleep
suspends execution of the calling process for the duration specified by
.Fa timeout .
An unmasked signal will cause it to terminate the sleep early,
regardless of the
.Dv SA_RESTART
value on the interrupting signal.
.Sh RETURN VALUES
If the
.Fn nanosleep
function returns because the requested duration has elapsed, the value
returned will be zero.
.Pp
If the
.Fn nanosleep
function returns due to the delivery of a signal, the value returned
will be \-1, and the global variable
.Va errno
will be set to indicate the interruption.
If
.Fa remainder
is non-null, the timespec structure it references is updated to contain the
unslept amount (the requested duration minus the duration actually slept).
.Sh ERRORS
If any of the following conditions occur, the
.Fn nanosleep
function shall return \-1 and set
.Va errno
to the corresponding value.
.Bl -tag -width Er
.It Bq Er EINTR
.Nm
was interrupted by the delivery of a signal.
.It Bq Er EINVAL
.Fa timeout
specified a nanosecond value less than zero or greater than 1000 million,
or a second value less than zero or greater than 100 million.
.It Bq Er EFAULT
Either
.Fa timeout
or
.Fa remainder
points to memory that is not a valid part of the process address space.
.El
.Sh SEE ALSO
.Xr sleep 1 ,
.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 ,
appeared in
.At v3 ,
but was removed when
.Xr alarm 3
was introduced into
.At v7 .
The
.Fn nanosleep
system call has been available since
.Nx 1.3
and was ported to
.Ox 2.1
and
.Fx 3.0 .