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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 in-
       finite 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  in-
       voked 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 3.74 of the	Linux  man-pages  project.   A
       description  of	the project, information about reporting bugs, and the
       latest	 version    of	  this	  page,	   can	   be	  found	    at
       http://www.kernel.org/doc/man-pages/.

Linux				  2008-12-05			     ATEXIT(3)

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON

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