1.\" Copyright (c) 1990, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" Chris Torek and the American National Standards Committee X3, 6.\" on Information Processing Systems. 7.\" 8.\" Redistribution and use in source and binary forms, with or without 9.\" modification, are permitted provided that the following conditions 10.\" are met: 11.\" 1. Redistributions of source code must retain the above copyright 12.\" notice, this list of conditions and the following disclaimer. 13.\" 2. Redistributions in binary form must reproduce the above copyright 14.\" notice, this list of conditions and the following disclaimer in the 15.\" documentation and/or other materials provided with the distribution. 16.\" 3. Neither the name of the University nor the names of its contributors 17.\" may be used to endorse or promote products derived from this software 18.\" without specific prior written permission. 19.\" 20.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" $OpenBSD: atexit.3,v 1.8 2007/05/31 19:19:31 jmc Exp $ 33.\" 34.Dd $Mdocdate: May 31 2007 $ 35.Dt ATEXIT 3 36.Os 37.Sh NAME 38.Nm atexit 39.Nd register a function to be called on exit 40.Sh SYNOPSIS 41.Fd #include <stdlib.h> 42.Ft int 43.Fn atexit "void (*function)(void)" 44.Sh DESCRIPTION 45The 46.Fn atexit 47function registers the given 48.Fa function 49to be called at program exit, whether via 50.Xr exit 3 51or via return from the program's 52.Fn main . 53Functions so registered are called in reverse order; 54no arguments are passed. 55At least 32 functions can always be registered, 56and more are allowed as long as sufficient memory can be allocated. 57.Pp 58.Fn atexit 59is very difficult to use correctly without creating 60.Xr exit 3 Ns -time 61races. 62Unless absolutely necessary, please avoid using it. 63.Sh RETURN VALUES 64.Rv -std atexit 65.Sh ERRORS 66.Bl -tag -width Er 67.It Bq Er ENOMEM 68No memory was available to add the function to the list. 69The existing list of functions is unmodified. 70.El 71.Sh SEE ALSO 72.Xr exit 3 73.Sh STANDARDS 74The 75.Fn atexit 76function conforms to 77.St -ansiC . 78