-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);
+
+/* Write to "path_tmp" "path" + "_tmp" and return a new file at that "path_tmp"
+ * open for writing. "path_tmp" is malloc()'d, must be freed externally.
+*/
+extern FILE * atomic_write_start(char * path, char ** path_tmp);