clean-shell

# Clean Shell Shell-specific conventions for writing, hardening, reviewing, and testing scripts. The core rules below always apply. Load the one reference file matching the task; don't load them all. | Task touches | File | |---|---| | Scripts that mutate live systems: deploy/apply, firewall/sshd/sudoers edits, systemd oneshot+timer units, ssh remote-exec, rollback, cleanup traps, idempotency | `references/defensive.md` | | `.shellcheckrc`, `# shellcheck disable=` directives, severity floors, exit codes, CI gating | `references/shellcheck.md` | | Bats tests: `.bats` files, `run`, `setup`/`teardown`, PATH-stub mocking, parallel jobs | `references/bats.md` | ## Core Rules - Pick `set` flags by intent and comment the reason next to them: `set -euo pipefail` for orchestration where any failure aborts; drop `-e` when steps may fail without aborting; `set -u` alone for long-running loops. A thin wrapper sets no flags and ends with `exec`. - Quote every expansion (`"$var"`, `"${arr[@]}"`, `"$(cmd)"`); `--` end-of-options guard before untrusted operands. - Validate input at the boundary into a checked value (`"${1:?msg}"`, a `case` integer guard); no call site re-tests a raw string. - Every `mktemp` gets an EXIT trap right after creation. Traps are best-effort: SIGKILL, OOM-kill, and power loss skip them. - Anything that mutates system state is check-then-act idempotent; add `flock` where concurrent runs are possible. - Never echo a generated secret; `set -x` tracing and `ps`/`/p...