+ err = fflush(f);
+ /*
+ * We must send one line (and one line only) in a single write
+ * call. In case of a write error, libc may accumulate the
+ * unwritten data and try to write it again later, resulting in a
+ * multi-line write. So we must explicitly ask it to throw away
+ * any such cached data:
+ */
+ __fpurge(f);
+ return fflush(f);