1.\" Copyright (c) 1986, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. All advertising materials mentioning features or use of this software 13.\" must display the following acknowledgement: 14.\" This product includes software developed by the University of 15.\" California, Berkeley and its contributors. 16.\" 4. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)sleep.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD: src/lib/libc/gen/sleep.3,v 1.12.2.3 2001/12/14 18:33:51 ru Exp $ 34.\" $DragonFly: src/lib/libc/gen/sleep.3,v 1.3 2007/09/08 20:50:49 swildner Exp $ 35.\" 36.Dd February 13, 1998 37.Dt SLEEP 3 38.Os 39.Sh NAME 40.Nm sleep 41.Nd suspend process execution for an interval measured in seconds 42.Sh LIBRARY 43.Lb libc 44.Sh SYNOPSIS 45.In unistd.h 46.Ft unsigned int 47.Fn sleep "unsigned int seconds" 48.Sh DESCRIPTION 49The 50.Fn sleep 51function suspends execution of the calling process until either 52.Fa seconds 53seconds have elapsed or a signal is delivered to the process and its 54action is to invoke a signal-catching function or to terminate the 55process. 56System activity may lengthen the sleep by an indeterminate amount. 57.Pp 58This function is implemented using 59.Xr nanosleep 2 60by pausing for 61.Fa seconds 62seconds or until a signal occurs. 63Consequently, in this implementation, 64sleeping has no effect on the state of process timers, 65and there is no special handling for 66.Dv SIGALRM . 67.Sh RETURN VALUES 68If the 69.Fn sleep 70function returns because the requested time has elapsed, the value 71returned will be zero. 72If the 73.Fn sleep 74function returns due to the delivery of a signal, the value returned 75will be the unslept amount (the requested time minus the time actually 76slept) in seconds. 77.Sh SEE ALSO 78.Xr nanosleep 2 , 79.Xr usleep 3 80.Sh STANDARDS 81The 82.Fn sleep 83function conforms to 84.St -p1003.1-90 . 85.Sh HISTORY 86A 87.Fn sleep 88function appeared in 89.At v7 . 90