Top 10 Terminal Commands

A practical tour of the terminal commands a developer uses every week.

October 2026 · Missing Semester

Researched and drafted with AI assistance, then reviewed by me. ← Back to Knowledge Base

The terminal is a window where you type commands instead of clicking. It looks old-fashioned, but it is faster for many jobs, and almost every developer tool expects you to use it. On a Mac it is the Terminal app; the program reading your commands is called the shell (on a Mac, usually zsh).

These are the ten groups of commands I actually use, taken from my own command history. Each line starting with # is a comment for you; the terminal ignores it.

1. Move around: cd, pwd, ls, clear 

pwd                              # print working directory: "where am I?"
ls                               # list files here
ls -lh                           # long list with human-readable sizes (12K, 3.4G)
ls -d .git                       # check one thing exists, without listing inside it
cd Documents                     # go into a folder
cd ..                            # go up one level
cd ~                             # go home (~ means your home folder)
cd ~/Desktop/my-project          # go straight to a path
cd "/Users/me/Documents/Build with AI"   # quotes when a name has spaces
clear                            # wipe the screen (nothing is deleted)

Press Tab to auto-complete names (type cd Do then Tab → cd Documents); it also adds the backslashes for spaces for you.

2. Read files and your history: cat, tail, history 

cat notes.md                     # print a whole file
tail -n 50 ~/.zsh_history        # print only the last 50 lines
history                          # your recent commands, numbered

tail is great for logs and big files, where cat would flood the screen.

3. Open and run things: open, ./script, python3 

open "My App.app"                # open a file or app as if you double-clicked it (Mac)
open .                           # open this folder in Finder
./dev.sh                         # run a script in this folder (./ means "here")
./dev.sh restart                 # ...with an argument
python3 -m pytest                # run a Python tool as a module (here: the tests)
python3 -m my_package status     # run your own package's command
python3 -c "print(2 + 2)"        # run one line of Python
.build/debug/HealthTracking      # run a program you just built
opencode                         # start a command-line app (here: an AI coding agent)
.venv/bin/mkdocs serve --dev-addr 127.0.0.1:8002   # run a tool from a project's virtual environment

If ./dev.sh says “permission denied”, the file is not marked as runnable. See section 9.

4. Install apps and tools: brew

Homebrew is the Mac’s app store for the terminal.

brew install node                # install a tool
brew install cmake libomp pnpm   # several at once
brew                             # with no arguments: show help

5. Language package managers: npm, nvm, pnpm, pip, uv

Each language has its own installer for libraries.

node -v                          # which version of Node.js?
nvm install                      # install the Node version this project asks for
nvm                              # with no arguments: show help
npm install                      # install the project's JavaScript libraries
npm run dev                      # run the project's "dev" script (see package.json)
npm run refresh -- --mode=missing   # everything after -- is passed to the script
corepack enable                  # turn on Node's built-in helper for pnpm/yarn
corepack prepare pnpm@11.0.9 --activate   # pin an exact pnpm version
pnpm -v
pnpm --dir frontend install      # install in a sub-folder without cd-ing into it
pip install -U pip setuptools wheel  # -U means upgrade
python3 -m pip install -U autogluon --extra-index-url https://download.pytorch.org/whl/cpu
                                 # also look in an extra package index (CPU-only PyTorch here)
python -m ensurepip --upgrade    # repair or install pip itself
uv --version                     # uv: a much faster Python installer

Tip: python3 -m pip makes sure you install into the same Python you run. Plain pip sometimes points to another one.

6. Install scripts from the web: curl ... | bash 

curl -fsSL https://example.com/install.sh | bash

Homebrew’s official form does the same thing a different way:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"

curl downloads the script; the | (pipe) hands it straight to bash to run. Homebrew, nvm and uv all install this way. It is convenient but it runs whatever the website sends, so only do it for sources you trust, typed from their official page.

7. Environment variables: export, source, eval

Settings that programs read, like which AI model to use.

export OPENAI_MODEL="gpt-5"      # set a variable for this terminal window
echo $OPENAI_MODEL               # read it back
source "$HOME/.local/bin/env"    # run a settings file in THIS shell (so its exports stick)
eval "$(ssh-agent -s)"           # run the commands that another program prints

Never type real API keys into the terminal. Every command is saved in ~/.zsh_history in plain text, so export OPENAI_API_KEY="sk-..." leaves your secret in a file anyone can read. Put keys in a .env file instead, add .env to .gitignore, and let the app load it. If a key ever lands in your history or in a commit: revoke it, make a new one, and delete those lines.

8. Ports and stuck programs: lsof, kill

“Port 8000 is already in use” means an old program is still running.

lsof -i :8000                    # who is using port 8000? (shows a PID number)
kill 29896                       # ask that program to stop
kill -9 29896                    # force it to stop
kill -9 29907 29909              # several at once
kill -9 $(lsof -ti :5173) 2>/dev/null   # find AND kill whatever uses port 5173, quietly

Try plain kill first; -9 gives the program no chance to save or clean up.

9. Permissions and disk space: chmod, df 

chmod 0600 ~/.ssh/my_key         # only I can read/write this file (SSH insists on this for keys)
chmod +x dev.sh                  # make a script runnable
df -h ~/Desktop                  # how much disk space is free? (-h = human-readable)

10. Remote computers: ssh 

ssh my-server                    # log in to another computer
ssh -T git@github.com            # test your GitHub key (see the Git post)

Typing ssh user@203.0.113.5 -i ~/.ssh/key every time is tedious. Give servers short names in ~/.ssh/config:

Host my-server
  HostName 203.0.113.5
  User ubuntu
  IdentityFile ~/.ssh/my_key

Now ssh my-server is enough.

Shell symbols worth knowing

Symbol Meaning Example
~ your home folder cd ~/Desktop
. / .. this folder / the folder above open ., cd ..
"..." or \ keep a name with spaces together cd "Build with AI"
\ at line end command continues on the next line long python3 script.py \ commands
| send output of one command into another curl ... | bash
$( ) use a command’s output inside another kill -9 $(lsof -ti :5173)
2>/dev/null hide error messages kill ... 2>/dev/null
-- “the rest is for the script, not for me” npm run refresh -- --rate=240
$VAR the value of a variable echo $HOME

And two keys: ↑ brings back your last command; Ctrl+C stops whatever is running.

Sources: MIT: The Missing Semester — The Shell · MIT: Shell Tools and Scripting · Homebrew · npm docs: npm run · uv docs · GitHub: Connecting with SSH