1.\" $OpenBSD: alarm.3,v 1.15 2016/01/28 22:11:39 jmc Exp $ 2.\" 3.\" Copyright (c) 1980, 1991, 1993, 1994 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. Neither the name of the University nor the names of its contributors 15.\" may be used to endorse or promote products derived from this software 16.\" without specific prior written permission. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 19.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 20.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 21.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 22.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 23.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 24.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 25.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 27.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 28.\" SUCH DAMAGE. 29.\" 30.Dd $Mdocdate: January 28 2016 $ 31.Dt ALARM 3 32.Os 33.Sh NAME 34.Nm alarm 35.Nd set signal timer alarm 36.Sh SYNOPSIS 37.In unistd.h 38.Ft unsigned int 39.Fn alarm "unsigned int seconds" 40.Sh DESCRIPTION 41.Bf -symbolic 42This is a simplified interface to 43.Xr setitimer 2 . 44.Ef 45.Pp 46The 47.Fn alarm 48function waits a count of 49.Ar seconds 50before asserting the terminating signal 51.Dv SIGALRM . 52When the signal has successfully been caught, 53.Fn alarm 54returns the amount of time left on the clock. 55The maximum number of 56.Ar seconds 57allowed 58is 100000000. 59.Pp 60If an alarm has been set with 61.Fn alarm , 62another call to 63.Fn alarm 64will supersede the prior call. 65The request 66.Fn alarm "0" 67voids the current 68alarm. 69.Sh RETURN VALUES 70If the call succeeds, any time left remaining from a previous call is returned. 71If an error occurs, the value \-1 is returned, and a more precise 72error code is placed in the global variable 73.Va errno . 74.Sh SEE ALSO 75.Xr setitimer 2 , 76.Xr sigaction 2 , 77.Xr sigsuspend 2 , 78.Xr signal 3 , 79.Xr sleep 3 , 80.Xr ualarm 3 81.Sh STANDARDS 82The 83.Fn alarm 84function conforms to 85.St -p1003.1-2008 . 86.Sh HISTORY 87An 88.Fn alarm 89system call appeared in the Programmer's Workbench (PWB/UNIX) 90and was ported to 91.At v7 . 92For 93.Bx 4.1c , 94it was reimplemented as a wrapper around the 95.Xr setitimer 2 96system call. 97