1ATEXIT(3) Linux Programmer's Manual ATEXIT(3)
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6 atexit - register a function to be called at normal process termination
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9 #include <stdlib.h>
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11 int atexit(void (*function)(void));
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14 The atexit() function registers the given function to be called at nor‐
15 mal process termination, either via exit(3) or via return from the pro‐
16 gram's main(). Functions so registered are called in the reverse order
17 of their registration; no arguments are passed.
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19 The same function may be registered multiple times: it is called once
20 for each registration.
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22 POSIX.1-2001 requires that an implementation allow at least ATEXIT_MAX
23 (32) such functions to be registered. The actual limit supported by an
24 implementation can be obtained using sysconf(3).
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26 When a child process is created via fork(2), it inherits copies of its
27 parent's registrations. Upon a successful call to one of the exec(3)
28 functions, all registrations are removed.
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31 The atexit() function returns the value 0 if successful; otherwise it
32 returns a nonzero value.
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35 SVr4, 4.3BSD, C89, C99, POSIX.1-2001.
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38 Functions registered using atexit() (and on_exit(3)) are not called if
39 a process terminates abnormally because of the delivery of a signal.
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41 If one of the functions registered functions calls _exit(2), then any
42 remaining functions are not invoked, and the other process termination
43 steps performed by exit(3) are not performed.
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45 POSIX.1-2001 says that the result of calling exit(3) more than once
46 (i.e., calling exit(3) within a function registered using atexit()) is
47 undefined. On some systems (but not Linux), this can result in an
48 infinite recursion; portable programs should not invoke exit(3) inside
49 a function registered using atexit().
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51 The atexit() and on_exit(3) functions register functions on the same
52 list: at normal process termination, the registered functions are
53 invoked in reverse order of their registration by these two functions.
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55 POSIX.1-2001 says that the result is undefined if longjmp(3) is used to
56 terminate execution of one of the functions registered atexit().
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58 Linux notes
59 Since glibc 2.2.3, atexit() (and on_exit(3)) can be used within a
60 shared library to establish functions that are called when the shared
61 library is unloaded.
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64 #include <stdio.h>
65 #include <stdlib.h>
66 #include <unistd.h>
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68 void
69 bye(void)
70 {
71 printf("That was all, folks\n");
72 }
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74 int
75 main(void)
76 {
77 long a;
78 int i;
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80 a = sysconf(_SC_ATEXIT_MAX);
81 printf("ATEXIT_MAX = %ld\n", a);
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83 i = atexit(bye);
84 if (i != 0) {
85 fprintf(stderr, "cannot set exit function\n");
86 exit(EXIT_FAILURE);
87 }
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89 exit(EXIT_SUCCESS);
90 }
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93 _exit(2), exit(3), on_exit(3)
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96 This page is part of release 3.53 of the Linux man-pages project. A
97 description of the project, and information about reporting bugs, can
98 be found at http://www.kernel.org/doc/man-pages/.
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102Linux 2008-12-05 ATEXIT(3)