Solid foundation in the command line

Why this matters

If you are learning C on this site, Terminal is not optional flavour. It is how you will compile programs, run them, and dig when something breaks. The commands below have survived about forty years of fashion in computing. Learn them once; they stay useful.

Windows folk can follow the same ideas with Windows Terminal or WSL. I work on macOS here — same POSIX family as Linux — because that is what I use to teach myself C.

A few words you will hear

People throw these around in conversation. You do not need to memorise a glossary; you just need to recognise them when they appear.

The Terminal is the window. Inside it, a shell (on a modern Mac usually zsh) reads what you type. The blinking line waiting for you is the prompt. What you type before Return is a command. Folders are almost always called directories in this world.

Opening Terminal

On macOS, Terminal is already installed. Open it from Launchpad, or hit ⌘ + Space, type Terminal, and press Return. You should land in your home directory — your personal corner of the disk.

How the disk is organised

Think of the file system as a tree. At the top sits root, written /. Everything else hangs underneath — applications, users, libraries — in parent and child directories.

A simplified map of the macOS tree — not every folder, just the idea

You have already seen this tree in Finder. Some system folders look faded because they are hidden. In the shell, hidden names simply start with a dot (.).

Same place, three views: diagram, Finder, Terminal

Walking around

One habit to lock in early: on macOS and Linux, names are case-sensitive. Desktop and desktop are not the same place.

When I am lost, I ask three questions: Where am I? What is here? How do I go somewhere else?

pwd

Prints the current working directory — the folder the shell thinks you are standing in. Fresh Terminal sessions usually start at home (~).

ls

Lists what is in a directory. On its own, it lists here:

You can point it elsewhere without moving — an absolute path from root:

Or a relative path: . means this directory, .. means the parent.

You can even list several places in one breath:

Flags like -la are in part 2.

cd

Change directory — the shell’s double-click. Watch the prompt update if it shows where you are:

Type cd alone and press Return — you are home again, from anywhere on the machine.

clear

The window fills with old output. Type clear (or press ⌘ + K on a Mac) so you can start at the top of the terminal screen again.

Addresses: absolute and relative

A pathname is simply the route to a place — how you tell the shell which Desktop, which project folder.

An absolute path always starts at / and walks the whole tree. When pwd prints a path, that is absolute: you can paste it into cd from anywhere and arrive.

Reading an absolute path left to right, from root outward

A relative path starts from where you already are. That is why .. is so useful — one step toward the parent — and why ./Desktop is usually just Desktop when you are already in the right parent.

Next

You can open Terminal, see the tree, and traverse it. That is enough to stop feeling lost.

Next we build a little sandbox and practise the commands that change things — create, copy, move, delete — in a folder we can throw away.

→ Command line: files and folders