al_vfprintf - Allegro 5 API

       Like  al_fprintf  but  takes  a  va_list.  Useful for creating your own variations of formatted printing.
       Returns the number of bytes written, or a negative number on error.

       al_vfprintf - Allegro 5 API

al_fprintf(3alleg5)

Allegro reference manual                                                                    al_vfprintf(3alleg5)

              #include <allegro5/allegro.h>

              int al_vfprintf(ALLEGRO_FILE *pfile, const char *format, va_list args)