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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ATTRIBUTES | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON |
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ATEXIT(3) Linux Programmer's Manual ATEXIT(3)
atexit - register a function to be called at normal process termina‐
tion
#include <stdlib.h>
int atexit(void (*function)(void));
The atexit() function registers the given function to be called at
normal process termination, either via exit(3) or via return from the
program's main(). Functions so registered are called in the reverse
order of their registration; no arguments are passed.
The same function may be registered multiple times: it is called once
for each registration.
POSIX.1 requires that an implementation allow at least ATEXIT_MAX
(32) such functions to be registered. The actual limit supported by
an implementation can be obtained using sysconf(3).
When a child process is created via fork(2), it inherits copies of
its parent's registrations. Upon a successful call to one of the
exec(3) functions, all registrations are removed.
The atexit() function returns the value 0 if successful; otherwise it
returns a nonzero value.
For an explanation of the terms used in this section, see
attributes(7).
┌──────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────┼───────────────┼─────────┤
│atexit() │ Thread safety │ MT-Safe │
└──────────┴───────────────┴─────────┘
POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.
Functions registered using atexit() (and on_exit(3)) are not called
if a process terminates abnormally because of the delivery of a
signal.
If one of the functions registered functions calls _exit(2), then any
remaining functions are not invoked, and the other process
termination steps performed by exit(3) are not performed.
POSIX.1 says that the result of calling exit(3) more than once (i.e.,
calling exit(3) within a function registered using atexit()) is
undefined. On some systems (but not Linux), this can result in an
infinite recursion; portable programs should not invoke exit(3)
inside a function registered using atexit().
The atexit() and on_exit(3) functions register functions on the same
list: at normal process termination, the registered functions are
invoked in reverse order of their registration by these two
functions.
According to POSIX.1, the result is undefined if longjmp(3) is used
to terminate execution of one of the functions registered using
atexit().
Linux notes
Since glibc 2.2.3, atexit() (and on_exit(3)) can be used within a
shared library to establish functions that are called when the shared
library is unloaded.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
void
bye(void)
{
printf("That was all, folks\n");
}
int
main(void)
{
long a;
int i;
a = sysconf(_SC_ATEXIT_MAX);
printf("ATEXIT_MAX = %ld\n", a);
i = atexit(bye);
if (i != 0) {
fprintf(stderr, "cannot set exit function\n");
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
_exit(2), dlopen(3), exit(3), on_exit(3)
This page is part of release 4.15 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2017-09-15 ATEXIT(3)
Pages that refer to this page: execve(2), _exit(2), dlopen(3), exit(3), on_exit(3), pmdaopenlog(3), pmfault(3), pmopenlog(3), pthread_atfork(3), pthread_exit(3)
Copyright and license for this manual page
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