atexit

    #include <stdlib.h>
    int atexit(void (*func)(void));
 

       The atexit function registers the given function to be called at normal
       process termination
 
       atexit returns the value 0 if successful, otherwise it returns
       a nonzero value.

#include <stdio.h> /* including standard library */
//#include <windows.h> /* uncomment this for Windows */
 
#include <stdlib.h>
 
void ExitMessage( void )
{
  printf("atexit was called, this is the exit message\n");
}
 
int main( void )
{
  atexit(ExitMessage);
 
  printf("The ExitMessage will shown after this line\n");
 
  return 0;
}

  user@host:~/code-reference.com#  ./atexit 
  The ExitMessage will shown after this line
  atexit was called, this is the exit message