bash-linux

A reference for using Bash, a command-line shell used on Linux and macOS, to work with files, processes, commands, and text.

In plain words
What is it for?
Use it to inspect files, search text, connect commands with pipelines, manage processes, write shell scripts, and handle command errors.
Why use it?
It makes shell work more predictable and helps avoid mistakes when chaining commands or handling failures.

Skill for Claude CodeCodex

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 skills/phuonghx/aim-cli/bash-linux
Any agent
npx skills add phuonghx/aim-cli --skill bash-linux
Clone the repo
git clone --depth 1 https://github.com/phuonghx/aim-cli

Made for: Claude Code, Codex.

Per session 51 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,506 The whole file, excluding the scripts and references it only reads on demand.
Security scan D 3 findings. 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 $0.00051 $0.01506
Opus 5 $0.00026 $0.00753
Sonnet 5 $0.00010 $0.00301
Haiku 4.5 $0.00005 $0.00151

Measured yesterday against content hash 244562677a8e, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade D, and why

bash-linux scanned grade D with 3 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 yesterday.

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.

Sends data to an external URLmediumData exfiltration

A POST to an outside endpoint may be telemetry or may be exfiltration; either way the mod talks to somewhere, and you should know where.

| POST a payload | `curl -X POST -H 'Content-Type: application/json' -d '{"id":7}' https://api.host/items` |

Recursive force deletehighDestructive command

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

finish() { rm -rf "$workdir"; }

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

| Save a download | `curl -fSL -O https://host/pkg.tar.gz` |
aim/templates/aim-agents/skills/bash-linux/SKILL.md · 190 lines

How it starts

The opening of the file, as written. The whole thing — 190 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Working in Bash on Unix Systems

A condensed field guide to getting things done in a POSIX shell.


1. Stringing Commands Together

The shell glues commands with a handful of operators. Pick the one that matches the relationship you want between steps.

Symbol Behavior Sample
; Always run the next one make clean; make
&& Continue only on success go build && ./app
|| React only to failure ping -c1 host || echo unreachable
| Feed stdout into the next command cat access.log | grep 404

2. Touching the Filesystem

Goal Command
Detailed listing ls -lah
Locate by name find . -type f -name '*.py'
Dump a file cat config.yaml
Top of a file head -n 30 report.txt
Bottom of a file tail -n 30 report.txt
Stream new lines tail -f server.log
Recursive text hunt grep -rn 'TODO' --include='*.go' .
Size of entries du -sh ./*
Free space df -h

3. Watching and Steering Processes

Goal Command
Snapshot everything ps aux
Filter by program pgrep -fl python
Terminate by id kill -TERM <pid> (escalate to -9 only if stuck)
Who holds a port lsof -i :8080
Free a port kill $(lsof -t -i :8080)
Detach a job ./worker &
List background jobs jobs -l
Resume in foreground fg %1

4. Reshaping Text

Utility Role Sample
grep Match lines grep -i 'error' app.log
sed Stream-edit sed -i 's/staging/prod/g' env.conf
awk Field logic awk -F: '{print $1}' /etc/passwd
cut Slice columns cut -d, -f2 sales.csv
sort Order lines sort -n nums.txt
uniq Collapse repeats sort names.txt | uniq -c
tr Translate chars tr 'a-z' 'A-Z' < in.txt
wc Tally wc -l data.txt

5. Environment Variables

Read the full file on GitHub · 190 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. yesterday First seen · 190 lines · 51 tokens per session scan D 244562677a8e

Subscribe to this mod's changes

bash-linux is a skill published in the GitHub repository phuonghx/aim-cli (1 stars, last pushed 2mo ago), licensed MIT. It adds 51 tokens to every session and 1,506 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it D with 3 findings (sends data to an external url, recursive force delete, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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