atexit(3) — Linux manual pages

Name

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

Synopsis

#include <stdlib.h>

int atexit( void (*function)(void));

DESCRIPTION

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.

POSIX.1-2001 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.

RETURN VALUE

The atexit() function returns the value 0 if successful; otherwise it returns a non-zero value.

CONFORMING TO

SVr4, 4.3BSD, C89, C99, POSIX.1-2001.

NOTES

Functions registered using atexit() (and on_exit(3)) are not called if a process terminates abnormally because of the delivery of a signal.

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.

EXAMPLE

#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");
       return EXIT_FAILURE;
    }
    return EXIT_SUCCESS;
}

  Copyright 1993 David Metcalfe (david@prism.demon.co.uk)

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

Since the Linux kernel and libraries are constantly changing, this
manual page may be incorrect or out-of-date.  The author(s) assume no
responsibility for errors or omissions, or for damages resulting from
the use of the information contained herein.  The author(s) may not
have taken the same level of care in the production of this manual,
which is licensed free of charge, as they might when working
professionally.

Formatted or processed versions of this manual, if unaccompanied by
the source, must acknowledge the copyright and authors of this work.

References consulted:
    Linux libc source code
    Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
    386BSD man pages
Modified 1993-03-29, David Metcalfe
Modified 1993-07-24, Rik Faith (faith@cs.unc.edu)
Modified 2003-10-25, Walter Harms

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