file_time - Returns the modification time of a file. Allegro game
programming library.
#include <allegro.h>
time_t file_time(const char *filename);
Returns the modification time (number of seconds since 00:00:00 GMT
1/1/1970) of a file. If the file does not exist or an error occurs, it
will return zero and store the system error code in errno.
file_exists(3alleg), file_size_ex(3alleg)