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.\" From: @(#)ualarm.3 8.2 (Berkeley) 4/19/94 29.\" $FreeBSD: src/lib/libc/gen/ualarm.3,v 1.9.2.5 2001/12/14 18:33:51 ru Exp $ 30.\" 31.Dd February 17, 2021 32.Dt UALARM 3 33.Os 34.Sh NAME 35.Nm ualarm 36.Nd schedule signal after specified time 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In unistd.h 41.Ft useconds_t 42.Fn ualarm "useconds_t microseconds" "useconds_t interval" 43.Sh DESCRIPTION 44.Bf -symbolic 45This is a simplified interface to 46.Xr setitimer 2 . 47.Ef 48.Pp 49The 50.Fn ualarm 51function 52waits a count of 53.Ar microseconds 54before asserting the terminating signal 55.Dv SIGALRM . 56System activity or time used in processing the call may cause a slight 57delay. 58.Pp 59If the 60.Fa interval 61argument is non-zero, the 62.Dv SIGALRM 63signal will be sent 64to the process every 65.Fa interval 66microseconds after the timer expires (e.g. after 67.Fa value 68microseconds have passed). 69.Pp 70Due to 71.Xr setitimer 2 72restriction the maximum number of 73.Ar microseconds 74and 75.Ar interval 76is limited to 100000000000000 77(in case this value fit in the unsigned integer). 78.Sh RETURN VALUES 79When the signal has successfully been caught, 80.Fn ualarm 81returns the amount of time left on the clock. 82.Sh NOTES 83A microsecond is 0.000001 seconds. 84.Sh SEE ALSO 85.Xr getitimer 2 , 86.Xr setitimer 2 , 87.Xr sigaction 2 , 88.Xr sigsuspend 2 , 89.Xr signal 3 , 90.Xr sleep 3 , 91.Xr usleep 3 92.Sh HISTORY 93The 94.Fn ualarm 95function appeared in 96.Bx 4.3 . 97