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.\" $FreeBSD$ 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.Ft int 48.Fn atexit_b "void (^function)(void)" 49.Sh DESCRIPTION 50The 51.Fn atexit 52function 53registers the given 54.Fa function 55to be called at program exit, whether via 56.Xr exit 3 57or via return from the program's 58.Fn main . 59Functions so registered are called in reverse order; 60no arguments are passed. 61.Pp 62These functions must not call 63.Fn exit ; 64if it should be necessary to terminate the process while in such a 65function, the 66.Xr _exit 2 67function should be used. 68(Alternatively, the function may cause abnormal 69process termination, for example by calling 70.Xr abort 3 . ) 71.Pp 72At least 32 functions can always be registered, 73and more are allowed as long as sufficient memory can be allocated. 74.Pp 75The 76.Fn atexit_b 77function behaves identically to 78.Fn atexit , 79except that it takes a block, rather than a function pointer. 80.\" XXX {ATEXIT_MAX} is not implemented yet 81.Sh RETURN VALUES 82.Rv -std atexit 83.Sh ERRORS 84.Bl -tag -width Er 85.It Bq Er ENOMEM 86No memory was available to add the function to the list. 87The existing list of functions is unmodified. 88.It Bq Er ENOSYS 89The 90.Fn atexit_b 91function was called by a program that did not supply a 92.Fn _Block_copy 93implementation. 94.El 95.Sh SEE ALSO 96.Xr at_quick_exit 3 , 97.Xr exit 3 98.Sh STANDARDS 99The 100.Fn atexit 101function 102conforms to 103.St -isoC . 104