The atexit() function registers the function pointed to by func to be called without arguments on normal termination of the program or when the object defining the function is unloaded.

Normal termination occurs by either a call to the exit(3C) function or a return from main(). Object unloading occurs when a call to dlclose(3DL) results in the object becoming unreferenced.

The number of functions that may be registered with atexit() is limited only by available memory (refer to the _SC_ATEXIT_MAX argument of sysconf(3C)).

After a successful call to any of the exec(2) functions, any functions previously registered by atexit() are no longer registered.

On process exit, functions are called in the reverse order of their registration. On object unloading, any functions belonging to an unloadable object are called in the reverse order of their registration.

Upon successful completion, the atexit() function returns 0. Otherwise, it returns a non-zero value.

The atexit() function may fail if:

ENOMEM

Insufficient storage space is available.

The functions registered by a call to atexit() must return to ensure that all registered functions are called.

There is no way for an application to tell how many functions have already been registered with atexit().

See attributes(5) for descriptions of the following attributes:

exec(2), dlclose(3DL), exit(3C), sysconf(3C), attributes(5)