Alex McFarlane

Useful Stuff

01: Basic Terminal Skills

Learning Outcomes

  • Be able to find / open the terminal
  • Be able to navigate filesystem within the Terminal
  • Basic usage of linux commands

Contents

Opening the Terminal

Why do I care? Basically because all the self help on the internet will rely on you being able to reproduce what you messed up in a minimal example. A lot of errors at the early stages are often to do with set up and nothing to do with python. Being able to run code in a minimal way in the terminal will give you confidence in programming in python and be able to isolate python issues from mor generic setup or configuration issues which can be very difficult to otherwise debug.

Opening a console on Mac OS X

OS X’s standard console is a program called Terminal. Open Terminal by navigating to Applications, then Utilities, then double-click the Terminal program. You can also easily search for it in the system search tool in the top right.

The command line Terminal is a tool for interacting with your computer. A window will open with a command line prompt message, something like this:

mycomputer:~ myusername$

Opening a console on Windows

Window’s console is called the Command Prompt, named cmd. However it sucks. I would always recommend using powershell. An easy way to powershell to it is by using the key combination Windows+R (Windows meaning the windows logo button), which should open a Run dialog. Then type powershell and hit Enter or click Ok. You can also search for it from the start menu. It should look like:

C:\Users\myusername>

Window’s powershell is not quite as powerful as its counterparts on Linux and OS X but they’ve copied all the relevant parts that we will want to use

Navigating around the Terminal

From this point onwards anything denoted like

$ program

will represent a Terminal interface (this is not python!). The above represents running a command named program in the Terminal.

Moving around directories

These commands will soon become second nature & after some practice they are quite a lot faster than navigating the user interface file explorer!

Check what directory you are in

$ pwd

show what’s in the current directory

$ ls

make a new directory

$ mkdir newdirectory

enter this directory

$ cd directory

go up one directory

$ cd ..

show whats inside the directory

$ ls directory/

remove a file

$ rm file.ext

Change the path (rename) a file (and / or extension)

$ mv directory/file.dat anotherdirectory/file2.csv

remove a directory (I probabaly wouldn’t do this hastily!)

$ rm -r directory

The -r is a known as a flag. This modifies the behaviour of the program rm. IN this instance it allows rm to delete directories which is otherwise a risky default ability.

These are pretty much all the commands you need. Try to familiarise yourself with them. All of these commands e.g. ls, rm, mkdir are all programs themselves that take in arguments from the command line depending on their operation.

Exercises

Your local machine home directory is always denoted by ~/ (note the slashes are backwards in Windows so this is ~\for Windows machines)

These exercises aim to get you more comfortable with using the command line rather than being an actual problem solving task

Exercise 1.1: Creating directories

  • cd into the directory ~
  • Create a new directory named temp in this directory

Exercise 1.2: Renaming directories

Change the name of this directory to pylrn

You can test this worked by doing

$ ls ~/pyl*

the * will wildcard all text following it

Exercise 1.3: Create a file with contents

Run the following command to create a new file

Max OS X users do this

$ touch ~/pylrn/test.py
$ echo print('Hello World') >> ~/pylrn/test.py

Windows users do this

$ "print('Hello World')" | Out-File ~/pylrn/test.py -encoding ascii

verify it is there with

$ ls ~/pylrn/*.py

Next Topic

02: Installing Python for Mac OS X / Windows