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.\" from: @(#)usleep.3 6.4 (Berkeley) 4/19/91 33.\" $Id: usleep.3,v 1.2 1993/07/30 08:40:26 mycroft Exp $ 34.\" 35.Dd April 19, 1991 36.Dt USLEEP 3 37.Os BSD 4.3 38.Sh NAME 39.Nm usleep 40.Nd suspend execution for interval of microseconds 41.Sh SYNOPSIS 42.Fd #include <unistd.h> 43.Ft void 44.Fn usleep "u_int microseconds" 45.Sh DESCRIPTION 46The 47.Fn sleep 48function 49suspends execution of the calling process 50for 51.Fa microseconds 52of time. 53System activity or time spent in processing the 54call may lengthen the sleep slightly. 55.Pp 56If a timer is already running on the process its state is saved. 57If the value 58.Fa microseconds 59is more than or equal to the remaining clock time for the saved timer, 60the sleep time is set to 61the remaining clock time. 62The state of the previous timer 63is restored after 64.Fa microseconds 65has passed. 66.Pp 67This routine is implemented using 68.Xr setitimer 2 ; 69it requires eight system calls each time it is invoked. 70A similar but less compatible function can be obtained with a single 71.Xr select 2 ; 72such a function would not restart after signals, but would not interfere 73with other uses of 74.Xr setitimer . 75.Sh SEE ALSO 76.Xr setitimer 2 , 77.Xr getitimer 2 , 78.Xr sigpause 2 , 79.Xr ualarm 3 , 80.Xr sleep 3 , 81.Xr alarm 3 82.Sh HISTORY 83The 84.Fn usleep 85function appeared in 86.Bx 4.3 . 87