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.\" $OpenBSD: sleep.3,v 1.18 2022/03/31 17:27:15 naddy Exp $
.\"
.\" Copyright (c) 1986, 1991, 1993
.\" The Regents of the University of California. All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" notice, this list of conditions and the following disclaimer.
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.\" notice, this list of conditions and the following disclaimer in the
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.\" 3. Neither the name of the University nor the names of its contributors
.\" may be used to endorse or promote products derived from this software
.\" without specific prior written permission.
.\"
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\"
.Dd $Mdocdate: March 31 2022 $
.Dt SLEEP 3
.Os
.Sh NAME
.Nm sleep
.Nd suspend execution for an interval of seconds
.Sh SYNOPSIS
.In unistd.h
.Ft unsigned int
.Fn sleep "unsigned int seconds"
.Sh DESCRIPTION
The
.Fn sleep
function suspends execution of the calling thread until at least the
given number of
.Fa seconds
have elapsed or an unmasked signal is delivered to the calling thread.
.Pp
This version of
.Fn sleep
is implemented with
.Xr nanosleep 2 ,
so delivery of any unmasked signal will terminate the sleep early,
even if
.Dv SA_RESTART
is set with
.Xr sigaction 2
for the interrupting signal.
.Sh RETURN VALUES
If
.Fn sleep
sleeps for the full count of
.Fa seconds ,
it returns 0.
Otherwise,
.Fn sleep
returns the number of seconds remaining from the original request.
.Sh ERRORS
The
.Fn sleep
function sets
.Va errno
to
.Dv EINTR
if it is interrupted by the delivery of a signal.
.Sh SEE ALSO
.Xr sleep 1 ,
.Xr nanosleep 2 ,
.Xr sigaction 2
.Sh STANDARDS
The
.Fn sleep
function conforms to
.St -p1003.1-2008 .
.Pp
Setting
.Va errno
is an extension to that specification.
.Sh HISTORY
A
.Fn sleep
system call first appeared in
.At v2 .
In
.At v7 ,
it was removed and replaced by a C library implementation based on
.Xr signal 3
and
.Xr alarm 3 .
For
.Ox 2.1 ,
it was reimplemented as a wrapper around the
.Xr nanosleep 2
system call.
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