1.\" Copyright (c) 1980, 1991, 1993, 1994 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.\" @(#)alarm.3 8.2 (Berkeley) 4/19/94 29.\" $FreeBSD$ 30.\" 31.Dd April 2, 2022 32.Dt ALARM 3 33.Os 34.Sh NAME 35.Nm alarm 36.Nd set signal timer alarm 37.Sh LIBRARY 38.Lb libc 39.Sh SYNOPSIS 40.In unistd.h 41.Ft unsigned int 42.Fn alarm "unsigned int seconds" 43.Sh DESCRIPTION 44.Bf -symbolic 45This interface is made obsolete by 46.Xr setitimer 2 . 47.Ef 48.Pp 49The 50.Fn alarm 51function sets a timer to deliver the signal 52.Dv SIGALRM 53to the calling process after the specified number of 54.Fa seconds . 55If an alarm has already been set with 56.Fn alarm 57but has not been delivered, another call to 58.Fn alarm 59will supersede the prior call. 60The request 61.Fn alarm "0" 62voids the current 63alarm and the signal SIGALRM will not be delivered. 64.Pp 65Due to 66.Xr setitimer 2 67restriction the maximum number of 68.Fa seconds 69allowed is 100000000. 70.Sh RETURN VALUES 71The return value of 72.Fn alarm 73is the amount of time left on the timer from a previous call to 74.Fn alarm . 75If no alarm is currently set, the return value is 0. 76.Sh SEE ALSO 77.Xr setitimer 2 , 78.Xr sigaction 2 , 79.Xr sigsuspend 2 , 80.Xr signal 3 , 81.Xr sleep 3 , 82.Xr ualarm 3 , 83.Xr usleep 3 84.\" .Sh STANDARDS 85.\" The 86.\" .Fn alarm 87.\" function conforms to 88.\" .St -p1003.1-90 . 89.Sh HISTORY 90An 91.Fn alarm 92system call appeared in the Programmer's Workbench (PWB/UNIX) 93and was ported to 94.At v7 . 95For 96.Bx 4.1c , 97it was reimplemented as a wrapper around the 98.Xr setitimer 2 99system call. 100