pdp11-ar

The archiver — authentic 2BSD ar, producing archives byte-identical in layout to what the native tool wrote.

pdp11-ar key [posname] afile name ...
   keys: d r q t p m x  + v c u a b i l

• The on-disk format is the point. The V7 26-byte member header and 0177545 magic assume 16-bit ints; here they are pinned to packed fixed widths, and ar_date/ar_size go through the PDPL() middle-endian swap — PDP-11 longs are stored high-word-first.
• Oracle-proven: rebuilding every archive in the 2.9BSD tree matches the native ar (run under apsim) 39/39, zero diffs.
• Member order is honoured, not normalised — ld lays out pulled members in archive order, so order is load-bearing for byte-identical linked output (see the libc Makefiles).

Documentation

• Design — the archive-format layouts, detection, the reader, and the one member-list writer.
• User guide — the operations and modifiers, choosing a write format per universe, and examples.
• docs/porting.md — the header-layout porting guide.

Build and test

make          # builds ../../bin/pdp11-ar
make check    # covered by tests/ld/ranlib.sh at the repo root and
              # the lib-sweep oracle