ATEXIT(3) - man page online | library functions

Register a function to be called at normal process termination.

ATEXIT(3)                           Linux Programmer's Manual                           ATEXIT(3)


atexit - register a function to be called at normal process termination


#include <stdlib.h> int atexit(void (*function)(void));


The atexit() function registers the given function to be called at normal process termina‐ tion, 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 registra‐ tion. 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 registra‐ tions. 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 termi‐ nates 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 per‐ formed. 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 regis‐ tration 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 atexit(). Linux notes Since glibc 2.2.3, atexit() (and on_exit(3)) can be used within a shared library to estab‐ lish 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)


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Linux 2015-08-08 ATEXIT(3)
This manual Reference Other manuals
atexit(3) referred by dlopen(3) | execve(2) | _exit(2) | exit(3) | explain_exit(3) | guestfs(3) | jemalloc(3) | log_open(3debug) | mem_open(3debug) | on_exit(3) | pmdaOpenLog(3) | __pmOpenLog(3) | pthread_exit(3)
refer to attributes(7) | dlopen(3) | exec(3) | _exit(2) | exit(3) | fork(2) | longjmp(3) | on_exit(3) | sysconf(3)