Bash/Linux terminal patterns. Critical commands, piping, error handling, scripting. Use when working on macOS or Linux systems.

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 7. Script Template 8. Common Patterns Check if command exists Default variable value Read file line by line Loop over files 9. Differences from PowerShell Task PowerShell Bash List files Get ChildItem ls la Find files Get ChildItem Recurse find . type f Environment $env:VAR $VAR String concat "$a$b" "$a$b" (same) Null check if ($x) if [ n "$x" ] Pipeline Object based Text based 10. Error Handling Set options Trap for cleanup Remember: Bash is text based. Use && for success chains, set e for safety, and quote your variables! When to Use This skill is applicable to execute the workflow or actions described in the overview. 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.

bash-linux