-extern int try_fgetc(FILE * file, char * f);
-extern char * try_fgets(char * line, int size, FILE * file, char * f);
+extern int try_fgetc(FILE * file, const char * f);
+extern char * try_fgets(char * line, int size, FILE * file, const char * f);
+
+/* Return "path" + suffix "_tmp". Value is malloc'd, must be freed externally.*/
+extern char * build_temp_path(char * path);