.\"	$OpenBSD: nanosleep.2,v 1.1 1997/04/20 20:56:20 tholo 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
.\" $FreeBSD: head/lib/libc/sys/nanosleep.2 197958 2009-10-11 16:23:11Z kib $
.\"
.Dd April 17, 1997
.Dt NANOSLEEP 2
.Os
.Sh NAME
.Nm nanosleep
.Nd suspend process 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
The
.Fn nanosleep
system call
causes the calling thread to sleep until the time interval specified by
.Fa rqtp
has elapsed.
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
system call returns because the requested time has elapsed, the value
returned will be zero.
.Pp
If the
.Fn nanosleep
system call 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 rmtp
is
.No non- Ns 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
system 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
The
.Fn nanosleep
system call
was interrupted by the delivery of a signal.
.It Bq Er EINVAL
The
.Fa rqtp
argument
specified a nanosecond value less than zero
or greater than or equal to 1000 million.
.It Bq Er ENOSYS
The
.Fn nanosleep
system call
is not supported by this implementation.
.El
.Sh SEE ALSO
.Xr sigsuspend 2 ,
.Xr sleep 3
.Sh STANDARDS
The
.Fn nanosleep
system call conforms to
.St -p1003.1b-93 .