1.\" $OpenBSD: sleep.3,v 1.8 2000/04/18 03:01:27 aaron 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. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.Dd June 4, 1993 35.Dt SLEEP 3 36.Os 37.Sh NAME 38.Nm sleep 39.Nd suspend process execution for interval of seconds 40.Sh SYNOPSIS 41.Fd #include <unistd.h> 42.Ft unsigned int 43.Fn sleep "unsigned int seconds" 44.Sh DESCRIPTION 45The 46.Fn sleep 47function suspends execution of the calling process until either the 48number of seconds specified by 49.Fa seconds 50have elapsed or a signal is delivered to the calling process and its 51action is to invoke a signal-catching function or to terminate the process. 52The suspension time may be longer than requested due to the 53scheduling of other activity by the system. 54.Pp 55This function is implemented using 56.Xr nanosleep 2 ; 57it requires one system call each time it is invoked. 58A similar but less compatible function can be obtained with a single 59.Xr select 2 ; 60such a function would not restart after signals, and also does not interfere 61with other uses of 62.Xr setitimer 2 63(not that 64.Fn sleep 65interferes with interval timers anymore). 66.Sh RETURN VALUES 67If the 68.Fn sleep 69function returns because the requested time has elapsed, the value 70returned will be zero. 71If the 72.Fn sleep 73function returns due to the delivery of a signal, the value returned 74will be the unslept amount (the request time minus the time actually 75slept) in seconds. 76.Sh SEE ALSO 77.Xr nanosleep 2 , 78.Xr select 2 , 79.Xr setitimer 2 , 80.Xr sigaction 2 , 81.Xr sigsuspend 2 , 82.Xr alarm 3 , 83.Xr pause 3 , 84.Xr usleep 3 85.Sh STANDARDS 86The 87.Fn sleep 88function conforms to 89.St -p1003.1-90 . 90.Sh HISTORY 91A 92.Fn sleep 93function appeared in 94.At v7 . 95