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.Dd February 11, 2021 29.Dt USLEEP 3 30.Os 31.Sh NAME 32.Nm usleep 33.Nd suspend thread execution for an interval measured in microseconds 34.Sh LIBRARY 35.Lb libc 36.Sh SYNOPSIS 37.In unistd.h 38.Ft int 39.Fn usleep "useconds_t microseconds" 40.Sh DESCRIPTION 41The 42.Fn usleep 43function suspends execution of the calling thread until either 44.Fa microseconds 45microseconds have elapsed or a signal is delivered to the thread and its 46action is to invoke a signal-catching function or to terminate the 47process. 48System activity may lengthen the sleep by an indeterminate amount. 49.Pp 50This function is implemented using 51.Xr nanosleep 2 52by pausing for 53.Fa microseconds 54microseconds or until a signal occurs. 55Consequently, in this implementation, 56sleeping has no effect on the state of process timers, 57and there is no special handling for SIGALRM. 58.Sh RETURN VALUES 59.Rv -std usleep 60.Sh ERRORS 61The 62.Fn usleep 63function 64will fail if: 65.Bl -tag -width Er 66.It Bq Er EINTR 67A signal was delivered to the calling thread and its 68action was to invoke a signal-catching function. 69.El 70.Sh SEE ALSO 71.Xr nanosleep 2 , 72.Xr sleep 3 73.Sh HISTORY 74The 75.Fn usleep 76function appeared in 77.Bx 4.3 . 78