al_set_path_filename - Allegro 5 API

       Set the optional filename part of the path.  The filename may be NULL, which is equivalent to setting the
       filename to the empty string.

       al_set_path_filename - Allegro 5 API

al_set_path_extension(3alleg5), al_get_path_filename(3alleg5)

Allegro reference manual                                                           al_set_path_filename(3alleg5)

              #include <allegro5/allegro.h>

              void al_set_path_filename(ALLEGRO_PATH *path, const char *filename)