1.\" $OpenBSD: sleep.3,v 1.11 2008/10/24 14:34:39 jmc Exp $ 2.\" 3.\" Copyright (c) 1986, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" Redistribution and use in source and binary forms, with or without 7.\" modification, are permitted provided that the following conditions 8.\" are met: 9.\" 1. Redistributions of source code must retain the above copyright 10.\" notice, this list of conditions and the following disclaimer. 11.\" 2. Redistributions in binary form must reproduce the above copyright 12.\" notice, this list of conditions and the following disclaimer in the 13.\" documentation and/or other materials provided with the distribution. 14.\" 3. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd $Mdocdate: October 24 2008 $ 31.Dt SLEEP 3 32.Os 33.Sh NAME 34.Nm sleep 35.Nd suspend process execution for interval of seconds 36.Sh SYNOPSIS 37.Fd #include <unistd.h> 38.Ft unsigned int 39.Fn sleep "unsigned int seconds" 40.Sh DESCRIPTION 41The 42.Fn sleep 43function suspends execution of the calling process until either the 44number of seconds specified by 45.Fa seconds 46have elapsed or a signal is delivered to the calling process and its 47action is to invoke a signal-catching function or to terminate the process. 48The suspension time may be longer than requested due to the 49scheduling of other activity by the system. 50.Pp 51This function is implemented using 52.Xr nanosleep 2 ; 53it requires one system call each time it is invoked. 54A similar but less compatible function can be obtained with a single 55.Xr select 2 ; 56such a function would not restart after signals, and also does not interfere 57with other uses of 58.Xr setitimer 2 59(not that 60.Fn sleep 61interferes with interval timers anymore). 62.Sh RETURN VALUES 63If the 64.Fn sleep 65function returns because the requested time has elapsed, the value 66returned will be zero. 67If the 68.Fn sleep 69function returns due to the delivery of a signal, the value returned 70will be the unslept amount (the request time minus the time actually 71slept) in seconds. 72.Sh SEE ALSO 73.Xr sleep 1 , 74.Xr nanosleep 2 , 75.Xr select 2 , 76.Xr setitimer 2 , 77.Xr sigaction 2 , 78.Xr sigsuspend 2 , 79.Xr alarm 3 , 80.Xr pause 3 , 81.Xr usleep 3 82.Sh STANDARDS 83The 84.Fn sleep 85function conforms to 86.St -p1003.1-90 . 87.Sh HISTORY 88A 89.Fn sleep 90function appeared in 91.At v7 . 92