Files
tai/research/shell-multiplexer-auto-attach/cyberciti-nixcraft-dollar-dash-test.md
T
retoorandClaude Sonnet 5 9dbd1fe667 Add plexer subsystem, container test infra, and last-resort opencode box backend
- Plexer: always-active terminal multiplexing. NativePlexerController/
  TmuxPlexerController share one interface, chosen by which env var is
  already set (TAI_PLEXER_SOCKET vs TMUX_PANE); NativePlexerBackend is
  the pty.fork()-based wrapper (raw mode, SIGWINCH resize forwarding,
  a Unix-socket control protocol, continuous session logging, a
  Ctrl+A prefix key distinct from tmux's own Ctrl+B). Auto-wraps new
  interactive shells via a .bashrc hook mirroring the existing
  command-not-found install pattern, gated on $TMUX/$TAI_PLEXER_ACTIVE/
  a $HOME/.tai-no-plexer bypass. New plexer_send/read/type/status
  tools, env-gated on a detected controller.
- tests/container.py + docker-compose.yml + tests/docker/Dockerfile:
  a disposable podman/docker image for the tests that must never touch
  a real machine (installing the plexer hook into a real ~/.bashrc, a
  live tmux session). Required suite (test_seal.py, test_tai.py,
  tests/plexer.py, tests/bashrc.py) gates the result; tests/rag.py
  runs as best-effort since its real-LLM dependency can't be satisfied
  inside a disposable container with no nested engine.
- tests/bashrc.py: real end-to-end hook install + bash -i auto-wrap,
  anti-recursion, tmux-active skip, non-interactive skip, a live
  TmuxPlexerController test, and an install/uninstall round-trip.
- tests/plexer.py: NativePlexerBackend under a real pty, plus a
  dedicated robustness pass (file permissions, >64KB payload framing,
  a malformed control request, a genuine self-deadlock fix in the
  write-to-child path).
- tai_test.py: the shared async process-driving framework (pipe/pty
  transport, group-wide kill-and-reap, a StdinBridge for --interactive)
  both test files build on.
- ChatClient last-resort backend: when there's no local opencode CLI
  but the sandbox box is already running, install opencode into it
  (official Node tarball, not apt -- apt's nodejs/npm pull in
  webpack/babel/jest as transitive deps) and route through it instead
  of giving up. Only reachable after the first retry round already
  failed everything else; never creates the box itself. TmuxPlexerController.status()
  fixed to use `list-panes` instead of `display-message -p`, which
  silently fell back to the default pane instead of erroring against
  a dead target.
- Fix 4 pre-existing test_tai.py bugs surfaced by running it in a
  clean environment for the first time: two stale mock signatures
  (subprocess.run's stdout= kwarg, Chat.complete's deadline= kwarg),
  one $TMUX-dependent catalog assertion, one tty-dependent color
  assertion.
- research/: a sourced research archive (Source Dossier/Citation
  Card/Conclusion tiers) backing the above design decisions, with its
  own audit.py consistency checker.
- .gitignore: fix a blanket *.md rule that was about to silently drop
  the entire research/ archive from version control; add __pycache__/
  and the one-off debug transcript this session started from.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
2026-10-10 04:36:05 +02:00

2.1 KiB

Bash Check If Shell Is Interactive or Not (nixCraft / cyberciti.biz)

Metadata

Field Value
Institute Molodetz Institute — Research & Retrieval Division
Subject shell-multiplexer-auto-attach
Document type Source Dossier
Tier 1
Source title Bash Check If Shell Is Interactive or Not Under Linux / Unix Oses
Source URL https://www.cyberciti.biz/faq/linux-unix-bash-check-interactive-shell/
Source publisher / author nixCraft (cyberciti.biz)
Source type blog post
Source date (published) Unknown — not stated
Date researched 2026-10-09
Researched by tai (agent), model: Claude Sonnet 5, on behalf of retoor
Research method web search synthesis
Confidence High
Status Active

Summary

A practical guide recommending the $- special parameter (which contains the literal character i when the shell is interactive) as the preferred interactivity test, with the standard idiom case "$-" in *i*) ... ;; esac.

Key findings

  • $- is bash's own exposed flag string, set to include i precisely when the shell meets bash's formal interactive definition — it's reading bash's own self-assessment, not re-deriving it from isatty() calls.
  • The canonical test form is a case statement matching *i* against $-.

Pros / strengths

  • Simple, portable within bash, and directly backed by bash's own internal state rather than an external inference.

Cons / limitations / caveats

  • Like any isatty-adjacent signal, $- containing i says "bash thinks it's interactive," which — per the query E dossiers in this subject — a pty-backed automation tool or AI agent terminal can also satisfy. It answers "is bash interactive" correctly; it does not answer "is a human present."

Relevance to tai

This is the first-line check for the proposal's auto-attach guard (.bashrc should do nothing at all unless $- contains i), but per this subject's conclusion, it must be combined with other signals, not used alone, to approximate "a human is here."

Changelog

Date Change
2026-10-09 Initial dossier created.