.\" $NetBSD: usleep.3,v 1.19.56.2 2024/07/20 15:19:39 martin Exp $ .\" .\" Copyright (c) 1986, 1991, 1993 .\" The Regents of the University of California. All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. Neither the name of the University nor the names of its contributors .\" may be used to endorse or promote products derived from this software .\" without specific prior written permission. .\" .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" @(#)usleep.3 8.1 (Berkeley) 6/4/93 .\" .Dd April 22, 2024 .Dt USLEEP 3 .Os .Sh NAME .Nm usleep .Nd suspend execution for interval of microseconds .Sh LIBRARY .Lb libc .Sh SYNOPSIS .In unistd.h .Ft int .Fn usleep "useconds_t microseconds" .Sh DESCRIPTION .Bf -symbolic This interface is obsoleted by .Xr nanosleep 2 . .Ef .Pp The .Fn usleep function suspends execution of the calling process until either the number of microseconds specified by .Fa microseconds have elapsed or a signal is delivered to the calling process and its action is to invoke a signal catching function or to terminate the process. The suspension time may be longer than requested due to the scheduling of other activity by the system. .Sh RETURN VALUES On successful completion, .Fn usleep returns 0. Otherwise, it returns \-1 and sets .Va errno to indicate the error. .Sh ERRORS The .Fn usleep function may fail if: .Bl -tag -width Er .It Bq Er EINTR .Nm was interrupted by the delivery of a signal. .El .Sh SEE ALSO .Xr nanosleep 2 , .Xr sleep 3 .Sh STANDARDS The .Fn usleep function conforms to .St -xpg4.2 . It later appeared in the .Tn POSIX standard, but in .St -p1003.1-2004 it was marked as legacy and the use of .Xr nanosleep 2 was recommended instead. The .St -p1003.1-2008 revision removed .Fn usleep from the specification. .Sh HISTORY The .Fn usleep function appeared in .Bx 4.3 . .Sh CAVEATS In .St -p1003.1-2004 , .Nm was limited to values of .Fa microseconds less than one million. Some implementations, including .Nx before 10.1, fail immediately with .Er EINVAL \(em and don't sleep at all \(em if .Fa microseconds is one million or greater.