The Ubuntu command line

The terminal shows a prompt and waits for a command:

alex@laptop:~$

That's username@computer:current-folder$. The ~ means your home folder, /home/<username>. In this workshop, a line starting with $ is the prompt; don't type the $ itself.

Where am I, and what's here?

pwd        # print working directory: the folder you're in
ls         # list what's in it
ls -la     # list everything, including hidden files, with details

Files and folders whose names start with . (like .gitignore) are hidden. ls -a shows them.

Moving around

cd Documents      # go into a folder
cd ..             # go up one folder
cd ~              # go home (plain `cd` does the same)
cd -              # go back to the previous folder

Two keys that save you hours

• Tab completes file and folder names. Type cd Doc and press Tab.
• Up brings back your previous commands.

Making and editing files

mkdir robot                 # make a folder
mkdir -p robot/src/drive    # make nested folders in one go
touch notes.txt             # make an empty file
nano notes.txt              # edit a file in the terminal
cat notes.txt               # print a file
less notes.txt              # scroll through a long file (press q to quit)

In nano, type normally, then press Ctrl+O then Enter to save and Ctrl+X to exit. The shortcuts are listed at the bottom of the screen (^ means Ctrl).

Prefer a graphical editor?

VS Code can open folders inside WSL (the WSL extension) or Multipass (the Remote - SSH extension). From an Ubuntu terminal in WSL, code . opens the current folder.

Copying, moving and deleting

cp notes.txt backup.txt         # copy a file
cp -r robot robot-old           # copy a folder (-r = recursive)
mv backup.txt old-notes.txt     # rename, or move
mv old-notes.txt robot/         # move into a folder
rm old-notes.txt                # delete a file
rm -r robot-old                 # delete a folder and everything in it

There's no recycle bin

rm deletes immediately and permanently. Double-check before you press Enter, especially with rm -r.

Installing software

Ubuntu installs software with apt:

sudo apt update           # refresh the list of available packages
sudo apt install tree     # install a package
tree                      # show the current folder as a tree

Getting help

ls --help       # quick summary of options
man ls          # the full manual (q to quit)

Stopping things

• Ctrl+C stops the running command.
• Ctrl+L (or clear) clears the screen.

Exercise

Build this layout in your home folder using only the terminal, then check it with tree ~/practice:

practice/
├── notes.txt         ← contains one line about yourself
└── robot/
    ├── drive/
    └── sensors/
        └── lidar.txt

One way to do it

cd ~
mkdir -p practice/robot/drive practice/robot/sensors
cd practice
nano notes.txt
touch robot/sensors/lidar.txt
tree ~/practice

When you're done, delete it with rm -r ~/practice.