2  The Command Line

Almost everything in this tutorial happens in a terminal, a text-based window where you type commands and the computer executes them. If you are used to clicking around in a graphical interface, the terminal can feel strange at first, but it quickly becomes the fastest way to get things done in scientific computing. This page gets you up and running with the handful of commands you actually need.

2.1 Opening your terminal

macOS - Open the built-in Terminal app. The easiest way is Spotlight: press ⌘ Space, type terminal, and press Enter.

Linux - Most desktop environments have a keyboard shortcut such as Ctrl+Alt+T, or you can find a Terminal entry in your applications menu.

Windows - Open PowerShell or Git Bash. For PowerShell, press Win, type powershell, and press Enter. Git Bash is installed alongside Git (see below) and provides a Unix-style shell that behaves identically to macOS and Linux terminals.

2.2 Navigating with pwd, ls, and cd

The terminal always has a working directory, the folder it is currently “inside”. Three commands let you find your bearings and move around:

• pwd - print working directory: shows the full path of where you are.
• ls - list the files and folders in the current directory.
• cd - change directory.

Here is a typical session. Start by checking where you are and what is there:

$ pwd
/home/user
$ ls
Desktop  Documents  Downloads  Pictures

Move into a folder:

$ cd Documents
$ ls
research  notes.txt

Go one level back up with cd ..:

$ cd ..
$ ls
Desktop  Documents  Downloads  Pictures

You can also jump straight to a path deeper in the tree:

$ cd Documents/research
$ ls
data  analysis.py

Those three commands are genuinely most of what you need to navigate the file system from the command line.

2.3 Getting this repository with git

git is a version-control tool that also lets you download a full copy of any public repository with one command. If you do not have git installed yet, get it from https://git-scm.com/install. If on Windows, this also installs Git Bash on Windows. Once installed, to get this tutorial’s code and materials, run:

$ git clone https://github.com/Tufts-University/py-onramp

This creates a new folder called py-onramp in your current directory. Step into it:

$ cd py-onramp
$ ls
code  docs  README.md

You now have everything you need locally. Head to Getting Started to set up your Python environment and run some code.