1.\" Copyright (c) 1986, 1991 Regents of the University of California. 2.\" 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 6.3 (Berkeley) 4/19/91 33.\" 34.Dd April 19, 1991 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 int 43.Fn sleep "u_int seconds" 44.Sh DESCRIPTION 45The 46.Fn sleep 47function 48suspends execution of the calling process 49for 50.Fa seconds 51of time. 52System activity or time spent in processing the 53call may lengthen the sleep by a second. 54.Pp 55If a timer is already running on the process its state is saved. 56If the value 57.Fa seconds 58is more than or equal to the remaining clock time for the saved timer, 59the sleep time is set to 60the remaining clock time. 61The state of the previous timer 62is restored after 63.Fa seconds 64has passed. 65.Pp 66This function is implemented using 67.Xr setitimer 2 ; 68it requires eight system calls each time it is invoked. 69A similar but less compatible function can be obtained with a single 70.Xr select 2 ; 71such a function would not restart after signals, but would not interfere 72with other uses of 73.Xr setitimer . 74.Sh RETURN VALUES 75.Sh SEE ALSO 76.Xr setitimer 2 , 77.Xr sigpause 2 , 78.Xr usleep 3 79.Sh HISTORY 80A 81.Fn sleep 82function appeared in 83.At v7 . 84