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.\" 31.Dd February 17, 2021 32.Dt USLEEP 3 33.Os 34.Sh NAME 35.Nm usleep 36.Nd suspend process execution for an interval measured in microseconds 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In unistd.h 41.Ft int 42.Fn usleep "useconds_t microseconds" 43.Sh DESCRIPTION 44The 45.Fn usleep 46function suspends execution of the calling process until either 47.Fa microseconds 48microseconds have elapsed or a signal is delivered to the process and its 49action is to invoke a signal-catching function or to terminate the 50process. 51System activity may lengthen the sleep by an indeterminate amount. 52.Pp 53This function is implemented using 54.Xr nanosleep 2 55by pausing for 56.Fa microseconds 57microseconds or until a signal occurs. 58Consequently, in this implementation, 59sleeping has no effect on the state of process timers, 60and there is no special handling for 61.Dv SIGALRM . 62.Sh RETURN VALUES 63.Rv -std usleep 64.Sh ERRORS 65The 66.Fn usleep 67function 68will fail if: 69.Bl -tag -width Er 70.It Bq Er EINTR 71A signal was delivered to the process and its 72action was to invoke a signal-catching function. 73.El 74.Sh SEE ALSO 75.Xr nanosleep 2 , 76.Xr sleep 3 77.Sh HISTORY 78The 79.Fn usleep 80function appeared in 81.Bx 4.3 . 82