103 lines
3.6 KiB
Groff
103 lines
3.6 KiB
Groff
.\" 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 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 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 2 .
|
|
.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 setitimer 2 ,
|
|
.Xr sigpause 2 ,
|
|
.Xr usleep 3
|
|
.Sh CAVEAT
|
|
In practice the FreeBSD implementation will not be interrupted: it will
|
|
always return the original argument or zero. Code that depends on
|
|
sleep being interrupted (using it as a timed pause, for example) needs
|
|
to be recoded to use
|
|
.Xr select 2
|
|
or some other delay mechanism. Code that
|
|
calls
|
|
.Fn sleep
|
|
repeatedly until it returns zero may busy-wait until a timer
|
|
is available.
|
|
.Sh HISTORY
|
|
A
|
|
.Fn sleep
|
|
function appeared in
|
|
.At v7 .
|