Software engineering blog · quick reference

SWE Cheatsheet ▋

Terminal commands for navigation, debugging, scripting, SSH, Python CLI, Git, and Docker in one practical sheet.

Published June 2026 · 6 min read · Hands-on workflow

$ command you type output # comment error

01 Navigation where am I?

pwd	Print working dir — "where am I?"
ls -laF	List: long, hidden, mark dirs with /
cd dir	Move into a folder
cd ..	Up one level (parent)
cd ~	Jump home from anywhere
cd -	Bounce to previous folder
mkdir d	Make a folder
touch f	Make an empty file

.HERE

..PARENT

~HOME

/ROOT

02 Reading errors debug

command not found

Typo or not installed. Fix: check spelling / install it

No such file or directory

Wrong folder. Fix: pwd, ls, fix the path

Permission denied

Not executable. Fix: ls -l, then chmod +x

THE LOOP

Read→ Reproduce→ Isolate→ 1 change→ Verify

03 Processes what's running?

ps aux	Snapshot — all processes now (PID, %CPU, %MEM)
top	Live view — auto-refreshing
htop	Friendlier live view (color, scroll)
kill PID	Stop politely (SIGTERM)
kill -9 PID	Force kill — last resort

Inside top: P cpu · M memory · q quit

04 Shell scripting automate

#!/bin/bash
# comment
name="Asha"  # no spaces around =
echo "Hi, $name!"
echo "Arg 1: $1"

chmod +x s.sh	1. Make it executable
./s.sh	2. Run it
$1 $2 $@	Arguments (one, two, all)
> >>	Redirect output (overwrite, append)

05 SSH remote machines

ssh user@hostname
ssh -p 2222 user@host
ssh-keygen -t ed25519
ssh user@host "ls -la"
exit  # come home

Private key stays on your laptop; public key goes on the server. First connect → type yes to the fingerprint. After connecting, every command runs on the remote machine.

06 Python via CLI run code

python3	REPL — >>> prompt; exit() or Ctrl-D
python3 app.py	Script — how real programs run
python3 -c "…"	One-liner inline
python3 -m http.server	Run a module as a program
sys.argv[1]	First command-line argument

⚠ Windows: native uses python / py; macOS / Linux / WSL use python3.

07 Git basics save history

git init	Start a repo
git status	What changed (your truth-teller)
git add .	Stage changes
git commit -m "…"	Save a snapshot
git log --oneline	View history, compact

Flow: working dir → add → staging → commit → repo. Always add before commit.

08 Git branching parallel work

git switch -c feature-x  # new branch
# …edit · add · commit…
git switch main
git merge feature-x
git branch  # list all
git log --oneline --graph --all

Never build on main directly. One branch per feature → merge when it works = the GitHub PR workflow. Old Git: checkout -b = switch -c.

09 Docker run anywhere

docker run hello-world	Verify install
docker run -it img cmd	Run interactively
docker ps -a	List containers (all)
docker images	List local images
docker build -t app .	Build image from Dockerfile
docker run app	Run your image

Image = recipe · Container = running instance. "Cannot connect to daemon" → start Docker Desktop.

Windows

Use Git Bash or WSL (Ubuntu). Avoid plain CMD/PowerShell. C: drive = /mnt/c/ in WSL.

macOS

Built-in Terminal, default shell zsh. Every command here works.

Linux

Built-in Terminal (bash). For Docker: sudo usermod -aG docker $USER, then re-login.