1.\" Copyright (c) 1990, 1991, 1993 2.\" The Regents of the University of California. 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.\" 4. 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.\" @(#)atexit.3 8.1 (Berkeley) 6/4/93 33.\" $FreeBSD$ 34.\" 35.Dd September 6, 2002 36.Dt ATEXIT 3 37.Os 38.Sh NAME 39.Nm atexit 40.Nd register a function to be called on exit 41.Sh LIBRARY 42.Lb libc 43.Sh SYNOPSIS 44.In stdlib.h 45.Ft int 46.Fn atexit "void (*function)(void)" 47.Sh DESCRIPTION 48The 49.Fn atexit 50function 51registers the given 52.Fa function 53to be called at program exit, whether via 54.Xr exit 3 55or via return from the program's 56.Fn main . 57Functions so registered are called in reverse order; 58no arguments are passed. 59.Pp 60These functions must not call 61.Fn exit ; 62if it should be necessary to terminate the process while in such a 63function, the 64.Xr _exit 2 65function should be used. 66(Alternatively, the function may cause abnormal 67process termination, for example by calling 68.Xr abort 3 . ) 69.Pp 70At least 32 functions can always be registered, 71and more are allowed as long as sufficient memory can be allocated. 72.\" XXX {ATEXIT_MAX} is not implemented yet 73.Sh RETURN VALUES 74.Rv -std atexit 75.Sh ERRORS 76.Bl -tag -width Er 77.It Bq Er ENOMEM 78No memory was available to add the function to the list. 79The existing list of functions is unmodified. 80.El 81.Sh SEE ALSO 82.Xr exit 3 83.Sh STANDARDS 84The 85.Fn atexit 86function 87conforms to 88.St -isoC . 89