idempotent-script-design
Use this skill when writing scripts, cron jobs, data pipelines, or any automated process that may be run multiple times. Design every operation to be safely re-runnable without side effects.
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- Repository
- aiming-lab/MetaClaw
- Last source activity
- March 10, 2026 at 18:04
- Detected SKILL.md language
- English
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- 3,467
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- 455
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- idempotent-script-design
- description
- Use this skill when writing scripts, cron jobs, data pipelines, or any automated process that may be run multiple times. Design every operation to be safely re-runnable without side effects.
- category
- automation
# Idempotent Script Design
An idempotent operation produces the same result whether run once or ten times.
**Techniques:**
- **Check before create:** `CREATE TABLE IF NOT EXISTS`, `mkdir -p`, check file existence before writing.
- **Upsert instead of insert:** Use `INSERT ... ON CONFLICT DO UPDATE` in SQL.
- **Atomic writes:** Write to a temp file, then rename — prevents corrupt partial output.
- **Track progress:** Write a completion marker or checkpoint so reruns skip done work.
**Testing idempotency:** Run your script twice on the same input and verify the output is identical.
**Anti-patterns:**
- Appending to a file without checking if the data is already there.
- Inserting rows without checking for duplicates.
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