DOKK / manpages / debian 11 / allegro5-doc / al_fsize.3alleg5.en
al_fsize(3alleg5) al_fsize(3alleg5)

al_fsize - Allegro 5 API

#include <allegro5/allegro.h>
int64_t al_fsize(ALLEGRO_FILE *f)
    

Return the size of the file, if it can be determined, or -1 otherwise.

Allegro reference manual