25.3. Exit Handlers

Sometimes, an application needs to automatically perform some operations on process termination. Consider the example of an application library that, if used during the life of the process, needs to have some cleanup actions performed automatically when the process exits. Since the library doesn’t have control of when and how the process exits, and can’t mandate that the main program call a library-specific cleanup function before exiting, cleanup is not guaranteed to occur. One approach in such situations is to use an exit handler (older System V manuals used the term program termination routine).

An exit handler is a programmer-supplied function that is registered at some point during the life of the process and is then automatically called during normal process termination via exit(). Exit handlers are not called if a program calls _exit() directly or if the process is terminated abnormally by a signal.