1ATEXIT(3P) POSIX Programmer's Manual ATEXIT(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
13 atexit — register a function to run at process termination
14
16 #include <stdlib.h>
17 int atexit(void (*func)(void));
19
21 The functionality described on this reference page is aligned with the
22 ISO C standard. Any conflict between the requirements described here
23 and the ISO C standard is unintentional. This volume of POSIX.1‐2008
24 defers to the ISO C standard.
25 The atexit() function shall register the function pointed to by func,
27 to be called without arguments at normal program termination. At normal
28 program termination, all functions registered by the atexit() function
29 shall be called, in the reverse order of their registration, except
30 that a function is called after any previously registered functions
31 that had already been called at the time it was registered. Normal
32 termination occurs either by a call to exit() or a return from main().
33 At least 32 functions can be registered with atexit().
35 After a successful call to any of the exec functions, any functions
37 previously registered by atexit() shall no longer be registered.
38
40 Upon successful completion, atexit() shall return 0; otherwise, it
41 shall return a non-zero value.
42
44 No errors are defined.
45 The following sections are informative.
47
49 None.
50
52 The functions registered by a call to atexit() must return to ensure
53 that all registered functions are called.
54 The application should call sysconf() to obtain the value of
56 {ATEXIT_MAX}, the number of functions that can be registered. There is
57 no way for an application to tell how many functions have already been
58 registered with atexit().
59 Since the behavior is undefined if the exit() function is called more
61 than once, portable applications calling atexit() must ensure that the
62 exit() function is not called at normal process termination when all
63 functions registered by the atexit() function are called.
64 All functions registered by the atexit() function are called at normal
66 process termination, which occurs by a call to the exit() function or a
67 return from main() or on the last thread termination, when the behavior
68 is as if the implementation called exit() with a zero argument at
69 thread termination time.
70 If, at normal process termination, a function registered by the
72 atexit() function is called and a portable application needs to stop
73 further exit() processing, it must call the _exit() function or the
74 _Exit() function or one of the functions which cause abnormal process
75 termination.
76
78 None.
79
81 None.
82
84 exec, exit(), sysconf()
85 The Base Definitions volume of POSIX.1‐2008, <stdlib.h>
87
89 Portions of this text are reprinted and reproduced in electronic form
90 from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
91 -- Portable Operating System Interface (POSIX), The Open Group Base
92 Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
93 cal and Electronics Engineers, Inc and The Open Group. (This is
94 POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
95 event of any discrepancy between this version and the original IEEE and
96 The Open Group Standard, the original IEEE and The Open Group Standard
97 is the referee document. The original Standard can be obtained online
98 at http://www.unix.org/online.html .
99 Any typographical or formatting errors that appear in this page are
101 most likely to have been introduced during the conversion of the source
102 files to man page format. To report such errors, see https://www.ker‐
103 nel.org/doc/man-pages/reporting_bugs.html .
104IEEE/The Open Group 2013 ATEXIT(3P)