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

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 nor-
       mal process termination, either via exit(3) or via return from the pro-
       gram'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.1-2001  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 nonzero 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.
       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.1-2001  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.
       POSIX.1-2001 says that 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 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");
               exit(EXIT_FAILURE);
           }
           exit(EXIT_SUCCESS);
       }
SEE ALSO
       _exit(2), exit(3), on_exit(3)
COLOPHON
       This page is part of release 3.53 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.

Linux                             2008-12-05                         ATEXIT(3)