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(libc.info)Cleanups on Exit

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Cleanups on Exit
----------------

   Your program can arrange to run its own cleanup functions if normal
termination happens.  If you are writing a library for use in various
application programs, then it is unreliable to insist that all
applications call the library's cleanup functions explicitly before
exiting.  It is much more robust to make the cleanup invisible to the
application, by setting up a cleanup function in the library itself
using `atexit' or `on_exit'.

 - Function: int atexit (void (*FUNCTION) (void))
     The `atexit' function registers the function FUNCTION to be called
     at normal program termination.  The FUNCTION is called with no
     arguments.

     The return value from `atexit' is zero on success and nonzero if
     the function cannot be registered.

 - Function: int on_exit (void (*FUNCTION)(int STATUS, void *ARG), void
          *ARG)
     This function is a somewhat more powerful variant of `atexit'.  It
     accepts two arguments, a function FUNCTION and an arbitrary
     pointer ARG.  At normal program termination, the FUNCTION is
     called with two arguments:  the STATUS value passed to `exit', and
     the ARG.

     This function is included in the GNU C library only for
     compatibility for SunOS, and may not be supported by other
     implementations.

   Here's a trivial program that illustrates the use of `exit' and
`atexit':

     #include <stdio.h>
     #include <stdlib.h>
     
     void
     bye (void)
     {
       puts ("Goodbye, cruel world....");
     }
     
     int
     main (void)
     {
       atexit (bye);
       exit (EXIT_SUCCESS);
     }

When this program is executed, it just prints the message and exits.