Master Bash Linux Command Patterns

Bash Linux Patterns is a reference skill for essential Bash commands and idioms on Linux/macOS, spanning ten areas: operator syntax for chaining commands (; sequential, && run-on-success, || run-on-failure, | pipe), file operations (ls -la, find -name -type f, cat, head/tail, tail -f for following logs, grep -r, du -sh, df -h), process management (ps aux, kill -9 <PID>, lsof -i :PORT to find and kill a port's owner, backgrounding with &, jobs -l, fg), and text processing (grep, sed -i for in-place replace, awk for column extraction, cut -d, sort -u, uniq -c, wc -l).

Use it when writing or debugging shell scripts and command-line workflows on Linux/macOS - environment variable handling (env/printenv, export VAR="value", appending to PATH), networking (curl -O to download, curl -X POST with a JSON body, nc -zv to check a port, ifconfig/ip addr), and a dedicated comparison table mapping PowerShell equivalents to Bash (Get-ChildItem to ls -la, $env:VAR to $VAR, object-based pipelines to text-based ones, if ($x) to if [ -n "$x" ]). It is not a PowerShell reference itself - that table exists only to orient users coming from PowerShell.

The skill provides a reusable script scaffold combining strict-mode error handling, colored logging, and a main entry point:

#!/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 "$@"

Common idioms covered on top of this: checking whether a command exists (command -v node &> /dev/null), defaulting an unset variable (NAME=${1:-"default_value"}), reading a file line by line with while IFS= read -r line, and looping over matching files with for file in *.js.

Error-handling options are broken out individually - set -e (exit on error), set -u (exit on undefined variable), set -o pipefail (exit on pipe failure), and set -x (debug: print each command) - plus a trap cleanup EXIT pattern for guaranteed cleanup on script exit, regardless of how the script terminates.

Developers writing Bash scripts or working the Linux/macOS command line who want a quick, reliable reference for command chaining, file/process/text-processing commands, safe script scaffolding, and common idioms rather than looking each one up individually.