int write_to_file(const char *filename);
int write_to_file(FILE *file, const char *filename="");
int read_from_file(const char *filename, int ignore_error = 0);
int write_to_file(const char *filename);
int write_to_file(FILE *file, const char *filename="");
int read_from_file(const char *filename, int ignore_error = 0);