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claude-foundations/best-practices/scripting.md
Paul O'Reilly e94417b896 Add best practices, hooks, memory files, and scripts from recent sessions
Includes: spec-driven and test-driven development best practices,
reproduce-before-fixing debugging workflow, require-plan-file hook,
find-project-root script, session logs, memory files for decisions/
gotchas/process-lessons, and updates to existing best practice topics.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-17 09:47:47 +13:00

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# Scripting Conventions
## Structure
- All scripts live in `scripts/` and run from the repository root
- Scripts should be idempotent and safe to re-run
- Exit non-zero on failure so `&&` chains work naturally
## Verification Scripts
- Automated checks confirming milestone or feature outcomes
- Use colour output (green/red) for pass/fail indicators
- Should be non-destructive and environment-resilient
- Avoid needing sudo — test from the accessible side of a connection instead
- Check for default/insecure credentials and print remediation instructions on failure
- Use `curl --resolve` to bypass DNS/proxy layers when testing direct connectivity
## Automation Triggers
If you run the same 3+ commands in sequence more than once, it should become a script. Look for:
- Repeated command sequences in conversation history
- Steps requiring careful ordering
- Multi-step manual processes that are error-prone
## Error Handling by Tool Purpose
Not all scripts need the same error handling strategy:
- **Destructive scripts** (deploy, configure, delete) should use `set -euo pipefail` — fail fast on any error.
- **Reporting/read-only scripts** (status dashboards, aggregation, monitoring) should start without `set -e` — complex data collection from multiple sources is hard to debug under errexit. Use explicit conditional checks instead.
- **The choice depends on the tool's purpose.** A script that writes to production needs strict error handling. A script that reads from 10 sources and aggregates results needs resilience.
## Dryrun Mode
Every script that modifies state should support `--dryrun` / `-n`:
- Makes the script self-documenting about its side effects
- Enables safe testing and review before execution
- Enables test harnesses that verify output without executing changes
- Dryrun output should show exactly what would happen, not a summary
## Shell Gotchas
- `((PASS++))` fails under `set -e` when PASS=0 — the expression evaluates to 0 (false), triggering errexit. Use `PASS=$((PASS + 1))` instead.
- `set -e` silently terminates complex pipelines and subshells with no output — makes debugging extremely difficult. Also kills command substitutions that capture non-zero exit codes (e.g., `result=$(grep "pattern" file)` exits if grep finds nothing).
- `grep` interprets option-like strings (starting with `-`) as flags — use `--` terminator before patterns or input that may start with dashes.
- Always quote variables in conditionals and file paths
- Use `trap` for cleanup of temp files and credentials