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14 .\" manual page may be incorrect or out-of-date.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 2017-09-15 "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
48 called at normal process termination, either via
50 or via return from the program's
52 Functions so registered are called in
53 the reverse order of their registration; no arguments are passed.
55 The same function may be registered multiple times:
56 it is called once for each registration.
58 POSIX.1 requires that an implementation allow at least
59 .\" POSIX.1-2001, POSIX.1-2008
61 (32) such functions to be registered.
62 The actual limit supported by an implementation can be obtained using
65 When a child process is created via
67 it inherits copies of its parent's registrations.
68 Upon a successful call to one of the
71 all registrations are removed.
75 function returns the value 0 if successful; otherwise
76 it returns a nonzero value.
78 For an explanation of the terms used in this section, see
84 Interface Attribute Value
87 T} Thread safety MT-Safe
91 POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
93 Functions registered using
97 are not called if a process terminates abnormally because
98 of the delivery of a signal.
100 If one of the registered functions calls
102 then any remaining functions are not invoked,
103 and the other process termination steps performed by
107 POSIX.1 says that the result of calling
108 .\" POSIX.1-2001, POSIX.1-2008
110 more than once (i.e., calling
112 within a function registered using
115 On some systems (but not Linux), this can result in an infinite recursion;
116 .\" This can happen on OpenBSD 4.2 for example, and is documented
117 .\" as occurring on FreeBSD as well.
118 .\" Glibc does "the Right Thing" -- invocation of the remaining
119 .\" exit handlers carries on as normal.
120 portable programs should not invoke
122 inside a function registered using
129 functions register functions on the same list:
130 at normal process termination,
131 the registered functions are invoked in reverse order
132 of their registration by these two functions.
134 According to POSIX.1, the result is undefined if
136 is used to terminate execution of one of the functions registered using
138 .\" In glibc, things seem to be handled okay
144 can be used within a shared library to establish functions
145 that are called when the shared library is unloaded.
155 printf("That was all, folks\en");
164 a = sysconf(_SC_ATEXIT_MAX);
165 printf("ATEXIT_MAX = %ld\en", a);
169 fprintf(stderr, "cannot set exit function\en");