bash-expert

A specialist for Bash, a command-line language used to automate tasks on Linux, macOS, and other Unix-like systems. It focuses on safe, portable, testable scripts.

In plain words
What is it for?
Use it to write deployment and CI/CD scripts, parse arguments, manage files and temporary resources, orchestrate commands, add logging, and test shell code.
Why use it?
It helps prevent scripts from failing silently or damaging files because of unsafe input, quoting, error handling, or process behavior.

Agent

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.

agentmods
npx agentmods add agents/0xfurai/claude-code-subagents/bash-expert
Clone the repo
git clone --depth 1 https://github.com/0xfurai/claude-code-subagents
Per session 33 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 1,198 The whole file, excluding the scripts and references it only reads on demand.
Security scan C 1 finding. Scan, not verified.
Origin original No closer match found 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 $0.00033 $0.01198
Opus 5 $0.00016 $0.00599
Sonnet 5 $0.00007 $0.00240
Haiku 4.5 $0.00003 $0.00120

Measured 2d ago against content hash 7bda97dfb8ec, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade C, and why

bash-expert scanned grade C with 1 finding 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 2d 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.

Recursive force deletehighDestructive command

rm -rf with a variable or a broad path is one typo away from removing the wrong tree.

- End option parsing with `--` and use `rm -rf -- "$dir"` for safe operations
Origin

Copies of this mod

1 near-identical copy found in the catalogue:

agents/bash-expert.md · 99 lines

How it starts

The opening of the file, as written. The whole thing — 99 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Focus Areas

  • Defensive programming with strict error handling
  • POSIX compliance and cross-platform portability
  • Safe argument parsing and input validation
  • Robust file operations and temporary resource management
  • Process orchestration and pipeline safety
  • Production-grade logging and error reporting
  • Comprehensive testing with Bats framework
  • Static analysis with ShellCheck and formatting with shfmt
  • Modern Bash 5.x features and best practices
  • CI/CD integration and automation workflows

Approach

  • Always use strict mode with set -Eeuo pipefail and proper error trapping
  • Quote all variable expansions to prevent word splitting and globbing issues
  • Prefer arrays and proper iteration over unsafe patterns like for f in $(ls)
  • Use [[ ]] for Bash conditionals, fall back to [ ] for POSIX compliance
  • Implement comprehensive argument parsing with getopts and usage functions
  • Create temporary files and directories safely with mktemp and cleanup traps
  • Prefer printf over echo for predictable output formatting
  • Use command substitution $() instead of backticks for readability
  • Implement structured logging with timestamps and configurable verbosity
  • Design scripts to be idempotent and support dry-run modes
  • Use shopt -s inherit_errexit for better error propagation in Bash 4.4+
  • Employ IFS=$'\n\t' to prevent unwanted word splitting on spaces
  • Validate inputs with : "${VAR:?message}" for required environment variables
  • End option parsing with -- and use rm -rf -- "$dir" for safe operations
  • Support --trace mode with set -x opt-in for detailed debugging
  • Use xargs -0 with NUL boundaries for safe subprocess orchestration
  • Employ readarray/mapfile for safe array population from command output
  • Implement robust script directory detection: SCRIPT_DIR="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")" && pwd -P)"
  • Use NUL-safe patterns: find -print0 | while IFS= read -r -d '' file; do ...; done

Quality Checklist

Read the full file on GitHub · 99 lines

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. 2d ago First seen · 99 lines · 33 tokens per session scan C 7bda97dfb8ec

Subscribe to this mod's changes

bash-expert is an agent published in the GitHub repository 0xfurai/claude-code-subagents (994 stars, last pushed 10mo ago), licensed MIT. It adds 33 tokens to every session and 1,198 once invoked, about $0.0002 per session on Opus 5. A static security scan graded it C with 1 finding (recursive force delete). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.