bash-linux

A guide to using Bash, the command-line shell commonly used on Linux and macOS, for files, processes, scripts, and command output.

In plain words
What is it for?
Use it when working in a Linux or macOS terminal, managing files and programs, inspecting logs, or writing shell scripts.
Why use it?
It provides ready patterns for common terminal tasks, including connecting commands, handling errors, and finding or stopping processes.

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/felipeslo/opencode-kit/bash-linux
Any agent
npx skills add felipeslo/opencode-kit --skill bash-linux
Clone the repo
git clone --depth 1 https://github.com/felipeslo/opencode-kit

Made for: Claude Code, Codex.

Per session 29 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 1,280 The whole file, excluding the scripts and references it only reads on demand.
Security scan B 2 findings. Scan, not verified.
Origin 97% 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 $0.00029 $0.01280
Opus 5 $0.00015 $0.00640
Sonnet 5 $0.00006 $0.00256
Haiku 4.5 $0.00003 $0.00128

Measured yesterday against content hash 58c80606d6fd, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade B, and why

bash-linux scanned grade B with 2 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 JSON | `curl -X POST -H "Content-Type: application/json" -d '{"key":"value"}' URL` |

Makes network callslowCapability

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

| Download | `curl -O https://example.com/file` |
Origin

This is a copy

97% identical to bash-linux — 3 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.

.opencode/skills/bash-linux/SKILL.md · 199 lines

How it starts

The opening of the file, as written. The whole thing — 199 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Bash Linux Patterns

Essential patterns for Bash on Linux/macOS.


1. Operator Syntax

Chaining Commands

Operator Meaning Example
; Run sequentially cmd1; cmd2
&& Run if previous succeeded npm install && npm run dev
|| Run if previous failed npm test || echo "Tests failed"
| Pipe output ls | grep ".js"

2. File Operations

Essential Commands

Task Command
List all ls -la
Find files find . -name "*.js" -type f
File content cat file.txt
First N lines head -n 20 file.txt
Last N lines tail -n 20 file.txt
Follow log tail -f log.txt
Search in files grep -r "pattern" --include="*.js"
File size du -sh *
Disk usage df -h

3. Process Management

Task Command
List processes ps aux
Find by name ps aux | grep node
Kill by PID kill -9 <PID>
Find port user lsof -i :3000
Kill port kill -9 $(lsof -t -i :3000)
Background npm run dev &
Jobs jobs -l
Bring to front fg %1

4. Text Processing

Core Tools

Tool Purpose Example
grep Search grep -rn "TODO" src/
sed Replace sed -i 's/old/new/g' file.txt
awk Extract columns awk '{print $1}' file.txt
cut Cut fields cut -d',' -f1 data.csv
sort Sort lines sort -u file.txt
uniq Unique lines sort file.txt | uniq -c
wc Count wc -l file.txt

5. Environment Variables

Task Command
View all env or printenv
View one echo $PATH
Set temporary export VAR="value"
Set in script VAR="value" command
Add to PATH export PATH="$PATH:/new/path"

6. Network

Task Command
Download curl -O https://example.com/file
API request curl -X GET https://api.example.com
POST JSON curl -X POST -H "Content-Type: application/json" -d '{"key":"value"}' URL
Check port nc -zv localhost 3000
Network info ifconfig or ip addr

Read the full file on GitHub · 199 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 · 199 lines · 29 tokens per session scan B 58c80606d6fd

Subscribe to this mod's changes

bash-linux is a skill published in the GitHub repository felipeslo/opencode-kit (2 stars, last pushed 5mo ago), licensed MIT. It adds 29 tokens to every session and 1,280 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it B with 2 findings (sends data to an external url, makes network calls). It is 97% identical to bash-linux, differing in 3 lines, and is treated as a copy.

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