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.\" $NetBSD: sleep.3,v 1.7 1995/02/27 05:51:44 cgd 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:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\" must display the following acknowledgement:
.\" This product includes software developed by the University of
.\" California, Berkeley and its contributors.
.\" 4. 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.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" @(#)sleep.3 8.1 (Berkeley) 6/4/93
.\"
.Dd June 4, 1993
.Dt SLEEP 3
.Os
.Sh NAME
.Nm sleep
.Nd suspend process execution for interval of seconds
.Sh SYNOPSIS
.Fd #include <unistd.h>
.Ft unsigned int
.Fn sleep "unsigned int seconds"
.Sh DESCRIPTION
The
.Fn sleep
function suspends execution of the calling process until either the
number of seconds specified by
.Fa seconds
have elapsed or a signal is delivered to the calling process and its
action is to invoke a signal-catching function or to terminate the
process. The suspension time may be longer than requested due to the
scheduling of other activity by the system.
.Pp
If a timer is already running on the process its state is saved.
If the value
.Fa seconds
is more than or equal to the remaining clock time for the saved timer,
the sleep time is set to
the remaining clock time.
The state of the previous timer
is restored after
.Fa seconds
has passed.
.Pp
This function is implemented using
.Xr setitimer 2 ;
it requires eight system calls each time it is invoked.
A similar but less compatible function can be obtained with a single
.Xr select 2 ;
such a function would not restart after signals, but would not interfere
with other uses of
.Xr setitimer .
.Sh RETURN VALUE
If the
.Fn sleep
function returns because the requested time has elapsed, the value
returned will be zero. If the
.Fn sleep
function returns due to the delivery of a signal, the value returned
will be the unslept amount (the request time minus the time actually
slept) in seconds.
.Sh SEE ALSO
.Xr setitimer 2 ,
.Xr sigaction 2 ,
.Xr sigsuspend 2 ,
.Xr alarm 3 ,
.Xr pause 3 ,
.Xr usleep 3
.Sh STANDARDS
The
.Fn sleep
function conforms to
.St -p1003.1-90 .
.Sh HISTORY
A
.Fn sleep
function appeared in
.At v7 .
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