man file_size_ex (3): Returns the size of a file in bytes. Allegro game programming library.

file_size_ex(3) Returns the size of a file in bytes. Allegro game programming library.

SYNOPSIS

#include <allegro.h>

uint64_t file_size_ex(const char *filename);

Returns the size of a file, in bytes. If the file does not exist or an error occurs, it will return zero and store the system error code in errno.