-struct string;
-struct substring;
-void fn_interp_vars (struct substring src,
- const char *(*getenv) (const char *),
- struct string *dst);
-char *fn_tilde_expand (const char *fn);
-char *fn_search_path (const char *base_name, const char *path,
- const char *prefix);
-char *fn_normalize (const char *fn);
-char *fn_dir_name (const char *fn);
-char *fn_extension (const char *fn);