1.\" $OpenBSD: usleep.3,v 1.5 1997/12/24 09:04:04 tholo 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. All advertising materials mentioning features or use of this software 15.\" must display the following acknowledgement: 16.\" This product includes software developed by the University of 17.\" California, Berkeley and its contributors. 18.\" 4. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.Dd November 4, 1997 35.Dt USLEEP 3 36.Os BSD 4.3 37.Sh NAME 38.Nm usleep 39.Nd suspend execution for interval of microseconds 40.Sh SYNOPSIS 41.Fd #include <unistd.h> 42.Ft int 43.Fn usleep "useconds_t microseconds" 44.Sh DESCRIPTION 45The 46.Fn usleep 47function 48suspends execution of the calling process 49for 50.Fa microseconds 51of time. 52System activity or time spent in processing the 53call may lengthen the sleep slightly. 54.Pp 55This routine is implemented using 56.Xr nanosleep 2 ; 57it requires one system call each time it is invoked. 58A similar but less compatible function can be obtained with a single 59.Xr select 2 ; 60such a function would not restart after signals, and also does not interfere 61with other uses of 62.Xr setitimer 63(not that 64.Fn usleep 65interferes with interval timers anymore.) 66.Sh RETURN VALUE 67If the 68.Fn usleep 69function returns because the requested time has elapsed, the value 70returned will be zero. 71.Pp 72If the 73.Fn usleep 74function returns due to the delivery of a signal, the value returned 75will be the -1, and the global variable 76.Va errno 77will be set to indicate the interruption. 78.Sh ERRORS 79If any of the following conditions occur, the 80.Nm 81function shall return -1 and set 82.Va errno 83to the corresponding value. 84.Bl -tag -width Er 85.It Bq Er EINTR 86.Nm 87was interrupted by the delivery of a signal. 88.It Bq Er EINVAL 89.Fa useconds 90specified a value of 1,000,000 or more microseconds. 91.El 92.Sh SEE ALSO 93.Xr getitimer 2 , 94.Xr nanosleep 2 , 95.Xr setitimer 2 , 96.Xr sigpause 2 , 97.Xr alarm 3 98.Xr sleep 3 , 99.Xr ualarm 3 , 100.Sh STANDARDS 101The 102.Fn usleep 103function conforms to 104.St -xpg4.2 . 105.Sh HISTORY 106The 107.Fn usleep 108function appeared in 109.Bx 4.3 . 110