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.\" @(#)usleep.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD: src/lib/libc/gen/usleep.3,v 1.10.2.7 2001/12/14 18:33:51 ru Exp $ 34.\" 35.Dd February 13, 1998 36.Dt USLEEP 3 37.Os 38.Sh NAME 39.Nm usleep 40.Nd suspend process execution for an interval measured in microseconds 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In unistd.h 45.Ft int 46.Fn usleep "unsigned int microseconds" 47.Sh DESCRIPTION 48The 49.Fn usleep 50function suspends execution of the calling process until either 51.Fa microseconds 52microseconds have elapsed or a signal is delivered to the process and its 53action is to invoke a signal-catching function or to terminate the 54process. 55System activity may lengthen the sleep by an indeterminate amount. 56.Pp 57This function is implemented using 58.Xr nanosleep 2 59by pausing for 60.Fa microseconds 61microseconds or until a signal occurs. 62Consequently, in this implementation, 63sleeping has no effect on the state of process timers, 64and there is no special handling for SIGALRM. 65.Sh RETURN VALUES 66.Rv -std usleep 67.Sh ERRORS 68The 69.Fn usleep 70function 71will fail if: 72.Bl -tag -width Er 73.It Bq Er EINTR 74A signal was delivered to the process and its 75action was to invoke a signal-catching function. 76.El 77.Sh SEE ALSO 78.Xr nanosleep 2 , 79.Xr sleep 3 80.Sh HISTORY 81The 82.Fn usleep 83function appeared in 84.Bx 4.3 . 85