“Command-line Computing” Exercise

Before we start learning about Python or software development, it will be helpful for us to achieve a basic level of familiarity with a command-line application. We use the command-line to navigate the computer’s filesystem, execute Python scripts, and perform other tasks using command-line utilities (CLIs).

Commands may differ based on which operating system and command-line application you’re using, but we should encouraged to learn the prevalent “unix-style” commands:

• On Mac OS, the default Terminal application will allow students to use unix-style commands.
• On Windows OS, the default Command Prompt application uses different commands, but installing the Git Bash application will allow students to use unix-style commands.

Additional References:

• Intro to the Command-Line - Mozilla

Walkthrough Video

Instructions

Open the Terminal application (Mac) or the Git Bash application (Windows).

After typing each of the commands below, press “enter” to execute it.

NOTE: You can copy and paste the commands, however on Git Bash you will need to right click to copy or paste, as keyboard shortcuts like “control + c” or “control + v” don’t work on Git Bash.

NOTE: You can optionally clear previous terminal output at any time by pressing “command + k” (Mac), or by typing clear and pressing “enter”.

Current User

Display the current user’s name:

whoami

Present Working Directory

Display the current/present working directory:

pwd

Listing Files in a Directory

List files in the current working directory:

ls

Alternatively, list files using a different display, including file permissions and hidden files:

ls -al

Navigating and Managing Directories

Change directories (specifying an absolute file path):

cd ~/Desktop

FYI: the tilde (~) represents your “home” filepath

FYI: you can use cd .. to move “up” one directory relative to the current working directory

Open a directory via the operating system’s filesystem explorer:

# Mac Terminal:
open .

# Windows Git Bash:
explorer .

Make a new directory:

mkdir my_folder

Remove a directory:

# triggers an error:
# rm my_folder

# uses options called flags to recursively (-r) force (-f) removal:
rm -rf my_folder

Managing Files

Setup a new directory in which to add some files, and navigate into that directory:

mkdir my_folder
cd my_folder

Create one or more files in the new directory you just created:

touch README.md
touch index.html
touch my_data.csv
touch my_message.txt

Remove a file:

rm index.html

Open a file in a text editor like VS Code (then edit it, and save it):

code my_message.txt

NOTE: Mac users may need to first configure the code command by following these VS Code shell command setup instructions

Display file contents:

cat my_message.txt

Move a file:

mv ~/Desktop/my_folder/my_message.txt ~/Desktop

FYI: If you are into maximum efficiency, press “tab” to auto-complete file paths so you don’t have to type the whole thing. 😺

Copy a file:

cp ~/Desktop/my_message.txt ~/Desktop/my_folder

Copy contents of a file into the clipboard for pasting:

# Mac OS:
pbcopy < ~/Desktop/my_folder/my_message.txt

# Windows OS:
cat ~/Desktop/my_folder/my_message.txt | clip

# ... then just paste as you normally would after copying some text

---

Further Exploration (Mac Only)

There are many other utilities to use from the command-line. For example, you may optionally try some of the examples below.

Making your computer speak:

say "Hello, I am your computer. Let's be friends."

Tracing the route traveled by a network request:

traceroute google.com
# ... stop after a few seconds if necessary by pressing: control + c

Timing the duration of a network request:

ping google.com
# ... stop after a few seconds if necessary by pressing: control + c

Requesting the contents of a webpage:

curl google.com

curl http://www.google.com

curl https://raw.githubusercontent.com/prof-rossetti/intro-to-python/master/data/products.json