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. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.\" @(#)usleep.3 8.1 (Berkeley) 6/4/93 29.\" $FreeBSD: src/lib/libc/gen/usleep.3,v 1.10.2.7 2001/12/14 18:33:51 ru Exp $ 30.\" $DragonFly: src/lib/libc/gen/usleep.3,v 1.3 2007/09/08 20:50:49 swildner Exp $ 31.\" 32.Dd February 13, 1998 33.Dt USLEEP 3 34.Os 35.Sh NAME 36.Nm usleep 37.Nd suspend process execution for an interval measured in microseconds 38.Sh LIBRARY 39.Lb libc 40.Sh SYNOPSIS 41.In unistd.h 42.Ft int 43.Fn usleep "unsigned int microseconds" 44.Sh DESCRIPTION 45The 46.Fn usleep 47function suspends execution of the calling process until either 48.Fa microseconds 49microseconds have elapsed or a signal is delivered to the process and its 50action is to invoke a signal-catching function or to terminate the 51process. 52System activity may lengthen the sleep by an indeterminate amount. 53.Pp 54This function is implemented using 55.Xr nanosleep 2 56by pausing for 57.Fa microseconds 58microseconds or until a signal occurs. 59Consequently, in this implementation, 60sleeping has no effect on the state of process timers, 61and there is no special handling for 62.Dv SIGALRM . 63.Sh RETURN VALUES 64.Rv -std usleep 65.Sh ERRORS 66The 67.Fn usleep 68function 69will fail if: 70.Bl -tag -width Er 71.It Bq Er EINTR 72A signal was delivered to the process and its 73action was to invoke a signal-catching function. 74.El 75.Sh SEE ALSO 76.Xr nanosleep 2 , 77.Xr sleep 3 78.Sh HISTORY 79The 80.Fn usleep 81function appeared in 82.Bx 4.3 . 83