# Shell Scripting

> Create, refactor, or review Bash shell scripts with strict mode, safe argument parsing, idempotent behavior, and rich CLI output (structured logs plus readable usage/help with color fallback). Use when users ask for .sh scripts, shell automation, CLI wrappers, or script hardening. Use when this capability is needed.

- Skill: `tomevault-io/shell-scripting-3` (Agent Skill, multi-file: 2 files)
- Install (CLI): `npx skillmds@latest add tomevault-io/shell-scripting-3`
- Raw SKILL.md: https://api.skillmd.com/api/skills/tomevault-io/shell-scripting-3/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: tomevault-io (https://skillmd.com/u/tomevault-io)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/tomevault-io/shell-scripting-3

---


# Shell Scripting

## Overview

Write scripts that are safe by default, easy to read, and predictable across repeated runs.
For new scripts, start from `assets/script-template.sh`.

## Workflow

1. Confirm scope and runtime assumptions (bash version, OS expectations, required tools).
2. Start from `assets/script-template.sh` and adapt it.
3. Keep parsing explicit (`-h`, `--help`, `--`) and fail on unknown flags.
4. Keep operations idempotent where practical (safe re-runs, no destructive defaults).
5. Validate with:
   - `bash -n <script>`
   - a small functional smoke run with safe inputs

## Output Style

Use structured output helpers:

- `log_error`: red + bold prefix (`ERROR:`), stderr
- `log_warn`: yellow, stderr
- `log_note`: dim informational note
- `log_success`: green success output

Use ANSI styling only when interactive:

- enable color when `-t 1` or `-t 2`
- disable color when `TERM=dumb` or `NO_COLOR` is set

Keep usage output readable:

- bold section headers (`Usage`, `Options`, `Examples`)
- highlight command examples in cyan
- keep notes concise and actionable

## Core Practices

- Use `#!/usr/bin/env bash` and `set -euo pipefail`.
- Quote variable expansions unless intentionally using word splitting.
- Use `local` for function-scoped variables.
- Prefer `printf` over `echo` for structured output.
- Validate required commands early (for example with `command -v` checks).
- Use `mktemp` for temporary files/dirs and cleanup with `trap`.
- Avoid destructive actions by default; require explicit opt-in for risky actions.
- Keep scripts composable and testable with small functions.

## Resources

- `assets/script-template.sh`: baseline script template with rich usage/log output.
- `references/best-practices.md`: expanded checklist and patterns.

---
> Converted and distributed by [TomeVault](https://tomevault.io/claim/nebius) — claim your Tome and manage your conversions.
<!-- tomevault:4.0:skill_md:2026-04-13 -->