105 lines
3.6 KiB
Groff
105 lines
3.6 KiB
Groff
.\" Copyright (c) 1986, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by the University of
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.\" California, Berkeley and its contributors.
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.\" 4. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)sleep.3 8.1 (Berkeley) 6/4/93
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.\"
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.Dd June 4, 1993
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.Dt SLEEP 3
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.Os
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.Sh NAME
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.Nm sleep
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.Nd suspend process execution for interval of seconds
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.Sh SYNOPSIS
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.Fd #include <unistd.h>
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.Ft u_int
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.Fn sleep "u_int seconds"
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.Sh DESCRIPTION
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The
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.Fn sleep
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function
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suspends execution of the calling process
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for
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.Fa seconds
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of time.
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System activity or time spent in processing the
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call may lengthen the sleep by a second.
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.Pp
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If a timer is already running on the process its state is saved.
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If the value
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.Fa seconds
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is more than or equal to the remaining clock time for the saved timer,
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the sleep time is set to
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the remaining clock time.
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The state of the previous timer
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is restored after
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.Fa seconds
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has passed.
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.Pp
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This function is implemented using
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.Xr setitimer 2 ;
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it requires eight system calls each time it is invoked.
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A similar but less compatible function can be obtained with a single
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.Xr select 2 ;
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such a function would not restart after signals, but would not interfere
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with other uses of
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.Xr setitimer 2 .
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.Sh RETURN VALUES
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The
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.Fn sleep
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function returns the number of seconds remaining to complete the operation. If
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sleep is interrupted or cannot allocate a timer it may will return the value
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needed to be passed to a subsequent sleep to complete the necessary delay.
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.Fn sleep
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repeatedly until it returns zero may busy-wait until a timer
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is available.
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.Sh SEE ALSO
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.Xr setitimer 2 ,
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.Xr sigpause 2 ,
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.Xr usleep 3
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.Sh CAVEAT
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In practice the
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.Tn FreeBSD
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implementation will not be interrupted: it will
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always return the original argument or zero. Code that depends on
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sleep being interrupted (using it as a timed pause, for example) needs
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to be recoded to use
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.Xr select 2
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or some other delay mechanism. Code that
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calls
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.Fn sleep
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repeatedly until it returns zero may busy-wait until a timer
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is available.
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.Sh HISTORY
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A
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.Fn sleep
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function appeared in
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.At v7 .
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