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.\" 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.
.\" 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
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" 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 u_int
.Fn sleep "u_int seconds"
.Sh DESCRIPTION
The
.Fn sleep
function
suspends execution of the calling process
for
.Fa seconds
of time.
System activity or time spent in processing the
call may lengthen the sleep by a second.
.Pp
If a timer is already running on the process its state is unaltered by
this
.Fn sleep
implementation.
If the value
.Fa seconds
is more than or equal to the remaining clock time for the running timer,
the sleep time is set to
the remaining clock time.
.Pp
This function is implemented using
.Xr signanosleep 2
by pausing for
.Fa seconds
of time or until any signal occurse.
For compatibility reasons SIGALRM signal handled internally
(if not blocked) during
.Fn sleep
call.
.Sh RETURN VALUES
The
.Fn sleep
function returns the number of seconds remaining to complete the operation. If
sleep is interrupted or cannot allocate a timer it may will return the value
needed to be passed to a subsequent sleep to complete the necessary delay.
.Fn sleep
repeatedly until it returns zero may busy-wait until a timer
is available.
.Sh SEE ALSO
.Xr alarm 3 ,
.Xr setitimer 2 ,
.Xr signal 3 ,
.Xr signanosleep 2 ,
.Xr ualarm 3 ,
.Xr usleep 3
.Sh HISTORY
A
.Fn sleep
function appeared in
.At v7 .
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