Regtransfers/bash-linux

@ 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

#!/bin/bash
set -euo pipefail  # Exit on error, undefined var, pipe fail

# Colors (optional)
RED='\033[0;31m'
GREEN='\033[0;32m'
NC='\033[0m'

# Script directory
SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"

# Functions
log_info() { echo -e "${GREEN}[INFO]${NC} $1"; }
log_error() { echo -e "${RED}[ERROR]${NC} $1" >&2; }

# Main
main() {
    log_info "Starting..."
    # Your logic here
    log_info "Done!"
}

main "$@"

@ 8. Common Patterns

@ Check if command exists

if command -v node &> /dev/null; then
    echo "Node is installed"
fi

@ Default variable value

NAME=${1:-"default_value"}

@ Read file line by line

while IFS= read -r line; do
    echo "$line"
done < file.txt

@ Loop over files

for file in *.js; do
    echo "Processing $file"
done

@ 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

set -e          # Exit on error
set -u          # Exit on undefined variable
set -o pipefail # Exit on pipe failure
set -x          # Debug: print commands

@ Trap for cleanup

cleanup() {
    echo "Cleaning up..."
    rm -f /tmp/tempfile
}
trap cleanup EXIT

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.
• never 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.