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