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

NAME
       atexit - register a function to be called at normal process termination

SYNOPSIS
       #include 

       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 ATEXITMAX
       (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 onexit(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  onexit(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  onexit(3))  can  be  used  within  a
       shared  library  to establish functions that are called when the shared
       library is unloaded.

EXAMPLE
       #include 
       #include 
       #include 

       void
       bye(void)
       {
           printf("That was all, folks\n");
       }

       int
       main(void)
       {
           long a;
           int i;

           a = sysconf(SCATEXITMAX);
           printf("ATEXITMAX = %ld\n", a);

           i = atexit(bye);
           if (i != 0) {
               fprintf(stderr, "cannot set exit function\n");
               exit(EXITFAILURE);
           }

           exit(EXITSUCCESS);
       }

SEE ALSO
       exit(2), exit(3), onexit(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)