{"id":7174,"date":"2022-12-20T19:35:43","date_gmt":"2022-12-20T22:35:43","guid":{"rendered":"http:\/\/lode.uno\/linux-man\/index.php\/2022\/12\/20\/atexit-man3\/"},"modified":"2022-12-20T19:35:43","modified_gmt":"2022-12-20T22:35:43","slug":"atexit-man3","status":"publish","type":"post","link":"https:\/\/lode.uno\/linux-man\/2022\/12\/20\/atexit-man3\/","title":{"rendered":"ATEXIT (man3)"},"content":{"rendered":"

ATEXIT<\/h1>\n

NAME<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
RETURN VALUE<\/a>
ATTRIBUTES<\/a>
CONFORMING TO<\/a>
NOTES<\/a>
EXAMPLES<\/a>
SEE ALSO<\/a>
COLOPHON<\/a> <\/p>\n

\n

NAME <\/a> <\/h2>\n

atexit \u2212 register a function to be called at normal process termination<\/p>\n

SYNOPSIS <\/a> <\/h2>\n

#include <\/b><\/p>\n

int atexit(void (*<\/b>function<\/i>)(void));<\/b><\/p>\n

DESCRIPTION <\/a> <\/h2>\n

The atexit<\/b>() function registers the given function<\/i> to be called at normal process termination, either via exit<\/b>(3) or via return from the program\u2019s main<\/i>(). Functions so registered are called in the reverse order of their registration; no arguments are passed.<\/p>\n

The same function may be registered multiple times: it is called once for each registration.<\/p>\n

POSIX.1 requires that an implementation allow at least ATEXIT_MAX<\/b> (32) such functions to be registered. The actual limit supported by an implementation can be obtained using sysconf<\/b>(3).<\/p>\n

When a child process is created via fork<\/b>(2), it inherits copies of its parent\u2019s registrations. Upon a successful call to one of the exec<\/b>(3) functions, all registrations are removed.<\/p>\n

RETURN VALUE <\/a> <\/h2>\n

The atexit<\/b>() function returns the value 0 if successful; otherwise it returns a nonzero value.<\/p>\n

ATTRIBUTES <\/a> <\/h2>\n

For an explanation of the terms used in this section, see attributes<\/b>(7).<\/p>\n\n\n\n
<\/td>\n <\/td>\n <\/td>\n<\/td>\n<\/td>\n <\/td>\n<\/tr>\n
<\/td>\n<\/td>\n <\/td>\n<\/td>\n<\/td>\n <\/td>\n<\/tr>\n<\/table>\n

\"Image<\/p>\n

CONFORMING TO <\/a> <\/h2>\n

POSIX.1-2001, POSIX.1-2008, C89, C99, SVr4, 4.3BSD.<\/p>\n

NOTES <\/a> <\/h2>\n

Functions registered using atexit<\/b>() (and on_exit<\/b>(3)) are not called if a process terminates abnormally because of the delivery of a signal.<\/p>\n

If one of the registered functions calls _exit<\/b>(2), then any remaining functions are not invoked, and the other process termination steps performed by exit<\/b>(3) are not performed.<\/p>\n

POSIX.1 says that the result of calling exit<\/b>(3) more than once (i.e., calling exit<\/b>(3) within a function registered using atexit<\/b>()) is undefined. On some systems (but not Linux), this can result in an infinite recursion; portable programs should not invoke exit<\/b>(3) inside a function registered using atexit<\/b>().<\/p>\n

The atexit<\/b>() and on_exit<\/b>(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.<\/p>\n

According to POSIX.1, the result is undefined if longjmp<\/b>(3) is used to terminate execution of one of the functions registered using atexit<\/b>().<\/p>\n

Linux notes<\/b>
Since glibc 2.2.3, atexit<\/b>() (and on_exit<\/b>(3)) can be used within a shared library to establish functions that are called when the shared library is unloaded.<\/p>\n

EXAMPLES <\/a> <\/h2>\n

#include
#include
#include <\/p>\n

void
bye(void)
{
printf(“That was all, folksn”);
}<\/p>\n

int
main(void)
{
long a;
int i;<\/p>\n

a = sysconf(_SC_ATEXIT_MAX);
printf(“ATEXIT_MAX = %ldn”, a);<\/p>\n

i = atexit(bye);
if (i != 0) {
fprintf(stderr, “cannot set exit functionn”);
exit(EXIT_FAILURE);
}<\/p>\n

exit(EXIT_SUCCESS);
}<\/p>\n

SEE ALSO <\/a> <\/h2>\n

_exit<\/b>(2), dlopen<\/b>(3), exit<\/b>(3), on_exit<\/b>(3)<\/p>\n

COLOPHON <\/a> <\/h2>\n

This page is part of release 5.10 of the Linux man-pages<\/i> 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\u2212pages\/.<\/p>\n

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