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nitpick-posix

The POSIX utility set, written in Nitpick — no libc, no C, no external dependency in any artifact.

Status: scaffolded. The repository exists, the scope question is recorded, and the planning pass has not been run. Nothing is implemented. When it runs it follows ../PLAYBOOK.md and the library playbook it defers to: specifications first, then decisions, then a cycle map, then code.

Why one repository

The utilities share far more than they differ by: argument parsing, the -- terminator, the --means-stdin convention, exit-status discipline, the diagnostic format, locale-free text handling, and a conformance suite measured against one standard. A hundred and sixty repositories would duplicate all of it and leave the shared behaviour with nowhere to live. The prototype reached the same conclusion — ARCHIVE/nitpick-posix is a single tree with a directory per utility.

The scope question, recorded rather than assumed

"POSIX utilities" is three different lists and the planning pass has to pick:

  • POSIX.1-2017 XCU — the ~160 utilities the standard actually defines.
  • What the prototype built — ARCHIVE/nitpick-posix has 264 .npk files and includes GNU coreutils additions (b2sum, base32, chcon) that are not in POSIX at all.
  • What is worth having — the intersection of "in the standard" and "somebody runs it", which is a much shorter list and is probably where a 1.0 should stop.

The planning pass decides, states the list, and states what is deliberately absent. A utility that is in the standard and not implemented is a stated departure; a utility that is implemented and not in the standard is a stated extension. Neither is a surprise.

What it consumes

Each utility names its own libraries, and the registry entry in ../APPS.md is the summary. Known so far:

Utility Library Note
grep nregex and a stated conformance departure — see below
date ntime POSIX +%Y formatting is parsed here and mapped onto ntime's typed layout; the library has no format-specifier language and does not need one

The grep departure, known before a line is written

POSIX basic regular expressions include back-references (\(…\) … \1), and nregex has none — by decision, because back-references are what force a backtracking engine, and catastrophic backtracking is a denial of service triggered by input somebody else controls.

grep is the tool most likely in the entire set to be pointed at hostile input. Adding a backtracking engine to it, to satisfy a conformance checkbox, would put the exact failure the regex library was designed to eliminate into the one program that most needs it eliminated. So:

a back-reference is refused, by name, with the reason and the byte offset — never silently accepted and never quietly reinterpreted. It is a documented conformance departure, it is the same choice ripgrep makes, and it is recorded here rather than discovered later.

Licence

Apache 2.0. See LICENSE.