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.\" 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.\" @(#)atexit.3 8.1 (Berkeley) 6/4/93 33.\" 34.Dd September 6, 2002 35.Dt ATEXIT 3 36.Os 37.Sh NAME 38.Nm atexit 39.Nd register a function to be called on exit 40.Sh LIBRARY 41.Lb libc 42.Sh SYNOPSIS 43.In stdlib.h 44.Ft int 45.Fn atexit "void (*function)(void)" 46.Ft int 47.Fn atexit_b "void (^function)(void)" 48.Sh DESCRIPTION 49The 50.Fn atexit 51function 52registers the given 53.Fa function 54to be called at program exit, whether via 55.Xr exit 3 56or via return from the program's 57.Fn main . 58Functions so registered are called in reverse order; 59no arguments are passed. 60.Pp 61These functions must not call 62.Fn exit ; 63if it should be necessary to terminate the process while in such a 64function, the 65.Xr _exit 2 66function should be used. 67(Alternatively, the function may cause abnormal 68process termination, for example by calling 69.Xr abort 3 . ) 70.Pp 71At least 32 functions can always be registered, 72and more are allowed as long as sufficient memory can be allocated. 73.Pp 74The 75.Fn atexit_b 76function behaves identically to 77.Fn atexit , 78except that it takes a block, rather than a function pointer. 79.\" XXX {ATEXIT_MAX} is not implemented yet 80.Sh RETURN VALUES 81.Rv -std atexit 82.Sh ERRORS 83.Bl -tag -width Er 84.It Bq Er ENOMEM 85No memory was available to add the function to the list. 86The existing list of functions is unmodified. 87.It Bq Er ENOSYS 88The 89.Fn atexit_b 90function was called by a program that did not supply a 91.Fn _Block_copy 92implementation. 93.El 94.Sh SEE ALSO 95.Xr at_quick_exit 3 , 96.Xr exit 3 97.Sh STANDARDS 98The 99.Fn atexit 100function 101conforms to 102.St -isoC . 103