atexit


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

       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 3.35 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://man7.org/linux/man-pages/.



Linux                             2008-12-05                         ATEXIT(3)
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