bash-defensive-patterns

bash-defensive-patterns is a skill for Claude Code, Codex from beel-collab/presets.dev. It costs 30 tokens per session (403 once invoked), scanned A, a copy of bash-defensive-patterns, MIT.

A guide to writing safer Bash shell scripts for automation and system tasks. It covers input checking, safe file handling, error handling, logging, testing, and compatibility across systems.

In plain words
What is it for?
Use it for deployment scripts, CI/CD pipelines, system utilities, administration tools, and other production shell automation.
Why use it?
It helps avoid common shell-script failures, unsafe variable use, and accidental damage. It is intended for scripts that must keep working when inputs or commands go wrong.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one.

Good fit Use it for deployment scripts, CI/CD pipelines, system utilities, administration tools, and other production shell automation.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/beel-collab/presets.dev/bash-defensive-patterns
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add beel-collab/presets.dev --skill bash-defensive-patterns
Clone the repo
git clone --depth 1 https://github.com/beel-collab/presets.dev

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for bash-defensive-patterns

README.md
[![agentmods](https://agentmods.dev/badge/skills/beel-collab/presets.dev/bash-defensive-patterns.svg)](https://agentmods.dev/skills/beel-collab/presets.dev/bash-defensive-patterns)
Your own site
<a href="https://agentmods.dev/skills/beel-collab/presets.dev/bash-defensive-patterns"><img src="https://agentmods.dev/badge/skills/beel-collab/presets.dev/bash-defensive-patterns.svg" alt="Measured on agentmods" height="20"></a>
Per session 30 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 403 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin 92% copy Near-identical to another mod in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00030 $0.00403
Opus 5 $0.00015 $0.00201
Sonnet 5 $0.00006 $0.00081
Haiku 4.5 $0.00003 $0.00040

Measured 3d ago against content hash f2d90937b810, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-07, from the pricing page.

Security

Grade A, and why

bash-defensive-patterns scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 3d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

Origin

This is a copy

92% identical to bash-defensive-patterns — 15 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

claude/skills/development/bash-defensive-patterns/SKILL.md · 53 lines

What it actually says

Bash Defensive Patterns

Comprehensive guidance for writing production-ready Bash scripts using defensive programming techniques, error handling, and safety best practices to prevent common pitfalls and ensure reliability.

Use this skill when

  • Writing production automation scripts
  • Building CI/CD pipeline scripts
  • Creating system administration utilities
  • Developing error-resilient deployment automation
  • Writing scripts that must handle edge cases safely
  • Building maintainable shell script libraries
  • Implementing comprehensive logging and monitoring
  • Creating scripts that must work across different platforms

Do not use this skill when

  • You need a single ad-hoc shell command, not a script
  • The target environment requires strict POSIX sh only
  • The task is unrelated to shell scripting or automation

Instructions

  1. Confirm the target shell, OS, and execution environment.
  2. Enable strict mode and safe defaults from the start.
  3. Validate inputs, quote variables, and handle files safely.
  4. Add logging, error traps, and basic tests.

Safety

  • Avoid destructive commands without confirmation or dry-run flags.
  • Do not run scripts as root unless strictly required.

Refer to resources/implementation-playbook.md for detailed patterns, checklists, and templates.

Resources

  • resources/implementation-playbook.md for detailed patterns, checklists, and templates.

Limitations

  • Use this skill only when the task clearly matches the scope described above.
  • Do not treat the output as a substitute for environment-specific validation, testing, or expert review.
  • Stop and ask for clarification if required inputs, permissions, safety boundaries, or success criteria are missing.
Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 3d ago First seen · 53 lines · 30 tokens per session scan A f2d90937b810

Subscribe to this mod's changes

bash-defensive-patterns is a skill published in the GitHub repository beel-collab/presets.dev (2 stars, last pushed 4mo ago), licensed MIT. It adds 30 tokens to every session and 403 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it A with 0 findings. It is 92% identical to bash-defensive-patterns, differing in 15 lines, and is treated as a copy.

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