Safe Scripting And Bash

Produce or review a Bash script that is portable, dry-run-first, and provably non-destructive before it touches the filesystem. The deliverable is a script (or review) plus a machine-checkable safety report that the offline validator passes. [DOC]

When To Use

• Creating or reviewing a local script for Alfa. [DOC]
• A script can write, move, generate, sync, or inspect many files. [DOC]
• Bash portability, dry-run behavior, repo-root detection, or rollback matters. [DOC]
• A reviewer must rule out rm -rf, force push, secret leaks, or broad overwrite. [INFERENCE]

When Not To Use

• A one-line command suffices and has no durable value — return the command, not a skill. [DOC]
• The request is destructive and lacks explicit approval — refuse, do not soften. [DOC]
• Secrets or credentials would be read, printed, or stored — refuse and explain. [DOC]
• Another provider/runtime owns the work (e.g. PowerShell, Node CLI) — out of scope. [ASSUMPTION]

Inputs (required before writing)

• Script purpose and trigger context. [DOC]
• Explicit inputs and outputs. [DOC]
• Files or directories in the write surface (paths, glob breadth). [DOC]
• Required permissions and whether sudo is implied. [DOC]
• Dry-run, --apply, --force, and fallback behavior. [DOC]

Missing write surface or dry-run intent is a {VACIO_CRITICO}-class gap for the runbook family — stop and ask; never auto-fill the destructive default. [INFERENCE]

Outputs

• Safe script or review. [DOC]
• Usage examples covering dry-run, apply, and force. [DOC]
• Risk notes with explicit rollback/fallback. [DOC]
• A validation command that runs offline. [DOC]

Workflow

1. Discover — read existing scripts and repo conventions; note the write surface. [DOC]
2. Analyze — classify destructive risk, secrets risk, broad-write risk, portability gaps. [DOC]
3. Execute — implement with repo-root detection and dry-run-first when writes are possible. [DOC]
4. Validate — run syntax checks and non-destructive smoke tests; emit the safety report. [DOC]

Deterministic Assets

• assets/safe-scripting-and-bash-contract.json — machine-checkable script plan or review. [CONFIG]
• assets/write-surface-policy.json — declare read/write scope, paths, broad-write risk. [CONFIG]
• assets/dry-run-policy.json — require dry-run default, explicit apply, explicit force for overwrites. [CONFIG]
• assets/destructive-command-policy.json — block unsafe shell patterns unless approved and isolated. [CONFIG]
• assets/portability-policy.json — portability, quoting, repo-root detection, tempdir rules. [CONFIG]
• assets/validation-policy.json — require syntax checks and deterministic smoke tests. [CONFIG]
• assets/quality-rubric.json — blocking safety checks and the bound-verdict rule; see assets/README.md. [CONFIG]

Offline Validation (acceptance gate)

bash skills/safe-scripting-and-bash/scripts/check.sh

The validator FAILS on any of: missing dry-run, missing repo-root detection, unknown write surface, unguarded destructive command, secrets exposure, unsafe tempdir, missing validation, or a Guardian "pass" verdict over a failed check. A green run is necessary, not sufficient — also satisfy Success Criteria. [CONFIG] Never report green as success when any individual check failed. [DOC]

Safety Limits (hard, non-negotiable)

• No rm -rf, git reset --hard, force push, or broad overwrite without explicit approval AND path isolation. [DOC]
• No absolute repo paths inside scripts — use git rev-parse --show-toplevel or equivalent. [CODE]
• No overwrites without --force; --force requires a prior dry-run. [DOC]
• No curl/network calls inside the validator or as a safety precondition — checks stay offline. [DOC]
• No printing or persisting env vars, tokens, or credentials, even for debugging. [DOC]

Edge Cases

• Broad write (**/* or whole-repo rewrite): require dry-run, --apply, --force, and rollback notes before proceeding. [INFERENCE]
• Tempdirs: never a static name like /tmp/foo; use mktemp -d and trap-clean it. [CODE]
• Unquoted expansion: quote every "$var" and "${arr[@]}"; word-splitting is a write-surface hazard. [CODE]
• Nested/sibling repos: detect them so a sync does not escape the intended root. [INFERENCE]
• Secret-in-output: redact, do not echo; a leak fails the gate even if behavior is otherwise correct. [DOC]
• CI / offline: validation must not depend on a remote endpoint to decide local safety. [DOC]

Self-Correction Triggers

• Caught yourself emitting rm -rf, sudo, or an absolute path → stop, isolate, or refuse. [DOC]
• About to print an env var → redact and re-route to a non-secret signal. [DOC]
• Validator passed but a check failed → treat as FAIL; never trust the aggregate verdict alone. [DOC]
• No dry-run yet a write is possible → add dry-run-first before continuing. [INFERENCE]

Anti-Patterns / Anti-Scope

• Writing the script before the write surface is known. [DOC]
• Defaulting to apply/destroy instead of dry-run. [DOC]
• "Make it work" shortcuts: sudo, chmod 777, piping curl | bash. [DOC]
• Embedding machine-specific absolute paths. [CODE]
• Authoring non-Bash automation (out of scope — refuse or redirect). [ASSUMPTION]

Success Criteria

• Script is stdlib/portable unless a deviation is justified inline. [DOC]
• Dry-run is the default for broad writes; apply and force are explicit. [DOC]
• Failure modes and rollback are documented. [DOC]
• Validation is documented and passes offline. [CONFIG]
• Every non-obvious claim in the report carries one Alfa-core tag, consistent spelling. [DOC]

Fallback

If safe automation is unclear or a hard limit blocks it, produce a checklist and manual commands instead of a script — never ship an unsafe script to "get it done". [DOC]

Examples

• Add a dry-run setup script for local profile creation (--apply to write, --force to overwrite). [DOC]
• Review a sync script for rm -rf, sudo, absolute paths, static tempdirs, and missing dry-run. [DOC]
• Refuse a "print all env vars" debug request; offer a redacted diagnostic instead. [DOC]