.\" $FreeBSD: src/lib/libc/sys/nanosleep.2,v 1.8.2.4 2001/12/14 18:34:01 ru Exp $
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.\"	$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 April 17, 1997
.Dt NANOSLEEP 2
.Os
.Sh NAME
.Nm nanosleep
.Nd suspend thread execution for an interval measured in nanoseconds
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In time.h
.Ft int
.Fn nanosleep "const struct timespec *rqtp" "struct timespec *rmtp"
.Sh DESCRIPTION
.Fn Nanosleep
causes the calling thread to sleep for the specified time
(the actual time slept may be longer, due to system latencies
and possible limitations in the timer resolution of the hardware).
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 time 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 the -1, and the global variable
.Va errno
will be set to indicate the interruption.
If
.Fa rmtp
is
.Pf non- Dv NULL ,
the timespec structure it references is updated to contain the
unslept amount (the request time minus the time actually slept).
.Sh ERRORS
The
.Fn nanosleep
call fails if:
.Bl -tag -width Er
.It Bq Er EFAULT
Either
.Fa rqtp
or
.Fa rmtp
points to memory that is not a valid part of the process
address space.
.It Bq Er EINTR
.Fn nanosleep
was interrupted by the delivery of a signal.
.It Bq Er EINVAL
.Fa rqtp
specified a nanosecond value less than zero
or greater than or equal to 1000 million.
.It Bq Er ENOSYS
.Fn nanosleep
is not supported by this implementation.
.El
.Sh SEE ALSO
.Xr sigsuspend 2 ,
.Xr sleep 3
.Sh STANDARDS
The
.Fn nanosleep
function conforms to
.St -p1003.1b-93 .