1.\" $NetBSD: usleep.3,v 1.4 1997/05/12 07:12:00 mikel 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.\" @(#)usleep.3 8.1 (Berkeley) 6/4/93 35.\" 36.Dd June 4, 1993 37.Dt USLEEP 3 38.Os BSD 4.3 39.Sh NAME 40.Nm usleep 41.Nd suspend execution for interval of microseconds 42.Sh SYNOPSIS 43.Fd #include <unistd.h> 44.Ft void 45.Fn usleep "u_int microseconds" 46.Sh DESCRIPTION 47The 48.Fn usleep 49function 50suspends execution of the calling process 51for 52.Fa microseconds 53of time. 54System activity or time spent in processing the 55call may lengthen the sleep slightly. 56.Pp 57If a timer is already running on the process its state is saved. 58If the value 59.Fa microseconds 60is more than or equal to the remaining clock time for the saved timer, 61the sleep time is set to 62the remaining clock time. 63The state of the previous timer 64is restored after 65.Fa microseconds 66has passed. 67.Pp 68This routine is implemented using 69.Xr setitimer 2 ; 70it requires eight system calls each time it is invoked. 71A similar but less compatible function can be obtained with a single 72.Xr select 2 ; 73such a function would not restart after signals, but would not interfere 74with other uses of 75.Xr setitimer 2 . 76.Sh SEE ALSO 77.Xr getitimer 2 , 78.Xr setitimer 2 , 79.Xr sigsuspend 2 , 80.Xr alarm 3 , 81.Xr ualarm 3 , 82.Xr sleep 3 83.Sh HISTORY 84The 85.Fn usleep 86function appeared in 87.Bx 4.3 . 88