| name | idempotent-shell-scripts |
| description | Create re-runnable infrastructure shell scripts for gcloud and bq that safely handle existing resources and produce deterministic outcomes across repeated executions. |
| metadata | {"author":"benthepsychologist","version":"1.0"} |
| compatibility | Requires bash with set -euo pipefail, authenticated gcloud CLI, and bq CLI in PATH. |
| allowed-tools | bash gcloud bq |
Idempotent Shell Scripts
Use this skill for bootstrap/provision scripts that must be safe to run many times.
Script baseline
#!/usr/bin/env bash
set -euo pipefail
PROJECT_ID="${PROJECT_ID:?PROJECT_ID is required}"
DATASET="${DATASET:-analytics}"
if ! bq --project_id "$PROJECT_ID" show --dataset "$DATASET" >/dev/null 2>&1; then
bq --project_id "$PROJECT_ID" mk --dataset "$DATASET"
fi
Patterns to apply
- Check-before-create for all resources.
- Prefer update/apply operations over delete/recreate.
- Gate destructive operations behind explicit flags.
- Validate required env vars at script start.
Verification
bash scripts/bootstrap.sh
bash scripts/bootstrap.sh
Second run must succeed without duplicating resources.
