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.

       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 3.54 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/.