1.\" $OpenBSD: usleep.3,v 1.19 2013/06/05 03:39:22 tedu 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd $Mdocdate: June 5 2013 $ 31.Dt USLEEP 3 32.Os 33.Sh NAME 34.Nm usleep 35.Nd suspend process execution for interval measured in microseconds 36.Sh SYNOPSIS 37.In unistd.h 38.Ft int 39.Fn usleep "useconds_t microseconds" 40.Sh DESCRIPTION 41.Bf -symbolic 42This interface is obsoleted by 43.Xr nanosleep 2 . 44.Ef 45.Pp 46The 47.Fn usleep 48function suspends execution of the calling process until either 49.Fa microseconds 50microseconds have elapsed or a signal is delivered to the process and its 51action is to invoke a signal-catching function or to terminate the 52process. 53The suspension time may be longer than requested due to the 54scheduling of other activity by the system. 55.Pp 56This function is implemented using 57.Xr nanosleep 2 58by pausing for 59.Fa microseconds 60microseconds or until a signal occurs. 61Consequently, in this implementation, 62sleeping has no effect on the state of process timers, 63and there is no special handling for 64.Dv 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 NOTES 78A microsecond is 0.000001 seconds. 79.Sh SEE ALSO 80.Xr sleep 1 , 81.Xr nanosleep 2 , 82.Xr sleep 3 83.Sh STANDARDS 84The 85.Fn usleep 86function conforms to 87.St -xpg4.2 . 88.Sh HISTORY 89The 90.Fn usleep 91function appeared in 92.Bx 4.3 . 93.Sh CAVEATS 94Some implementations of 95.Fn usleep 96return an error if 97.Fa microseconds 98is greater than or equal to 1,000,000. 99Portable applications should be written with this limitation in mind. 100