1 .\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
3 .\" %%%LICENSE_START(VERBATIM)
4 .\" Permission is granted to make and distribute verbatim copies of this
5 .\" manual provided the copyright notice and this permission notice are
6 .\" preserved on all copies.
8 .\" Permission is granted to copy and distribute modified versions of this
9 .\" manual under the conditions for verbatim copying, provided that the
10 .\" entire resulting derived work is distributed under the terms of a
11 .\" permission notice identical to this one.
13 .\" Since the Linux kernel and libraries are constantly changing, this
14 .\" manual page may be incorrect or out-of-date. The author(s) assume no
15 .\" responsibility for errors or omissions, or for damages resulting from
16 .\" the use of the information contained herein. The author(s) may not
17 .\" have taken the same level of care in the production of this manual,
18 .\" which is licensed free of charge, as they might when working
21 .\" Formatted or processed versions of this manual, if unaccompanied by
22 .\" the source, must acknowledge the copyright and authors of this work.
25 .\" References consulted:
26 .\" Linux libc source code
27 .\" Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
29 .\" Modified 1993-03-29, David Metcalfe
30 .\" Modified 1993-07-24, Rik Faith (faith@cs.unc.edu)
31 .\" Modified 2003-10-25, Walter Harms
33 .TH ATEXIT 3 2008-12-05 "Linux" "Linux Programmer's Manual"
35 atexit \- register a function to be called at normal process termination
38 .B #include <stdlib.h>
40 .BI "int atexit(void (*" function )(void));
45 function registers the given \fIfunction\fP to be
46 called at normal process termination, either via
48 or via return from the program's \fImain\fP().
49 Functions so registered are called in
50 the reverse order of their registration; no arguments are passed.
52 The same function may be registered multiple times:
53 it is called once for each registration.
55 POSIX.1-2001 requires that an implementation allow at least
57 (32) such functions to be registered.
58 The actual limit supported by an implementation can be obtained using
61 When a child process is created via
63 it inherits copies of its parent's registrations.
64 Upon a successful call to one of the
67 all registrations are removed.
71 function returns the value 0 if successful; otherwise
72 it returns a nonzero value.
74 SVr4, 4.3BSD, C89, C99, POSIX.1-2001.
76 Functions registered using
80 are not called if a process terminates abnormally because
81 of the delivery of a signal.
83 If one of the functions registered functions calls
85 then any remaining functions are not invoked,
86 and the other process termination steps performed by
90 POSIX.1-2001 says that the result of calling
92 more than once (i.e., calling
94 within a function registered using
97 On some systems (but not Linux), this can result in an infinite recursion;
98 .\" This can happen on OpenBSD 4.2 for example, and is documented
99 .\" as occurring on FreeBSD as well.
100 .\" Glibc does "the Right Thing" -- invocation of the remaining
101 .\" exit handlers carries on as normal.
102 portable programs should not invoke
104 inside a function registered using
111 functions register functions on the same list:
112 at normal process termination,
113 the registered functions are invoked in reverse order
114 of their registration by these two functions.
116 POSIX.1-2001 says that the result is undefined if
118 is used to terminate execution of one of the functions registered
120 .\" In glibc, things seem to be handled okay
126 can be used within a shared library to establish functions
127 that are called when the shared library is unloaded.
137 printf("That was all, folks\en");
146 a = sysconf(_SC_ATEXIT_MAX);
147 printf("ATEXIT_MAX = %ld\en", a);
151 fprintf(stderr, "cannot set exit function\en");