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