fix(builtins): xargs and empty pipes give stdin at EOF; printf %q keeps UTF-8 text

[chaliy]

Requested by Михайло · project thread

What changed

• xargs runs each command with stdin at EOF, as GNU xargs does with /dev/null, so printf '' | xargs wc -l prints 0.
• An empty pipe now reaches compound commands and functions as stdin at EOF instead of no stdin: printf '' | { wc -l; } prints 0.
• printf %q leaves printable non-ASCII text unescaped (bashkit runs as UTF-8): com\ espaço, not com\ espa\ço. Non-ASCII control characters use $'\ooo'.

Why

Two Debian-oracle cases found by the roadmap thread (pipeline-common-agent, printf-q-roundtrip). The xargs one turned out to be a general bug: an empty pipeline stdin was dropped before reaching the command.

Before / After

$ printf '' | xargs wc -l; printf '' | { wc -l; }; printf '%q\n' 'com espaço'
before:  (nothing) / (nothing) / com\ espa\ço
after:   0 / 0 / com\ espaço        # = bash 5.2, LANG=C.UTF-8

Risk

• Low. Commands reading an empty pipe now see an empty stdin rather than none; read, cat and friends already treat both as EOF. Full test suite passes.

Checklist

• Tests added or updated
• Backward compatibility considered

---

Generated by Claude Code

[cloudflare-workers-and-pages]

Deploying with    Cloudflare Workers

The latest updates on your project. Learn more about integrating Git with Workers.

Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	bashkit	27c3148	Commit Preview URL Branch Preview URL	Oct 08 2026, 02:16 AM