Navigating the Filesystem

Linux has no drive letters. There is no C:. Everything — every disk, every USB stick, every device, every file — hangs off a single tree that starts at /, called the root.

Getting comfortable at the command line is mostly getting comfortable moving around this tree without looking at it.

Three commands do almost everything

pwd tells you where you are. ls shows you what's here. cd moves you somewhere else. That's the loop, and you'll run it thousands of times.

Notice the third command printed nothing. That's not a failure — it's the Unix convention that silence means success. Commands that worked usually say nothing at all. If you wanted reassurance, you'd have to ask for it with pwd.

Absolute and relative paths

A path starting with / is absolute — it's measured from the root of the tree, so it means the same thing no matter where you are:

cd /var/log

A path not starting with / is relative — it's measured from wherever you currently are:

cd projects/website

Relative paths are shorter to type and are what you'll use most. Absolute paths are unambiguous and are what you'll use in scripts, where "wherever you currently are" isn't something you can rely on.

There are four shorthands worth memorising today:

• . — the current directory
• .. — the parent directory (one level up)
• ~ — your home directory, e.g. /home/you
• - — the directory you were in before the last cd, which makes cd - a toggle between two places

Reading ls properly

Bare ls gives you names. The options are where it gets useful:

ls -l     # long format: permissions, owner, size, modified date
ls -a     # include hidden files (anything starting with a dot)
ls -lh    # long format, human-readable sizes (4.0K instead of 4096)
ls -lt    # sort by modification time, newest first

Options can be combined, so ls -lah is the same as ls -l -a -h and is worth building into muscle memory.

"Hidden" files aren't secure or special — the rule is literally just "the name starts with a dot". It's a convention to keep config files (.bashrc, .gitignore, .env) out of your way. ls -a reveals them.

Let the shell type for you

Press Tab while typing a path and the shell will complete it. Press it twice and it shows you every possibility.

This is not a nicety. Tab completion is the difference between the command line feeling slow and feeling fast, and it doubles as a correctness check — if Tab won't complete what you're typing, the thing you're referring to probably doesn't exist. Experienced people almost never type a full path.

Next: creating, moving, and deleting things — including the one command that has no undo.