Learning Objectives

After this lesson, students will be able to:

• recognize the elements of the unix shell
• will be able to use paths to files and directories
• understand the difference between absolute and relative paths

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Day 1

Intro

• the data life cycle homework review
• Computers (and programming) are key tools for data science
• “Introducing the Shell” reading discussion:
  • What is a GUI?
  • What is a command shell?
    • A command-line interface (CLI); how else do we interact with computers? Interfaces exercise.
    • A scripting language; what is a scripting language? High-level languages presentation.
      • Banksy fetch
      • Programming and scripting languages provide a set of written rules that give instructions to a computational device (such as a computer) to perform a set of tasks.
      • “Programming languages are artificial languages that can be used to control the behaviour of a machine, particularly a computer”.
      • Different programming and scripting languages have different strengths.
  • Why would I use the command shell? What are the strengths of the shell?
  • Explain how the shell relates to the keyboard, the screen, the operating system, and users’ programs.
  • Explain when and why command-line interfaces should be used instead of graphical interfaces.
  • What is the prompt?

Navigating Files and Directories (40 min)

• SWC lesson
• the file system
• command pwd
• the home directory and its variations
• the two meaning of the “forward slash” /
• the command ls
• getting help with man ls
• the option ls -F
• options that throw errors
• explore other directories with ls -F Desktop
• changing locations down the file system with cd
• going up in the file system with ..
• . means the current directory
• ls -F -a
• using cd with no argument to go back home
• using the “tilde” ~ as shortcut of the current home directory
• using cd - to go back
• defining commands, options and arguments
• other names for options and arguments are parameters, switches or flags

• capitalization is meaningful, example: ls -s vs ls -S

• Joint exercise Absolute vs Relative Paths
• Solo exercise Relative Path Resolution

Working With Files and Directories (50 min)

• SWC lesson
• creating directories with mkdir and mkdir -p
  • Read 10 Best Practices for Naming Files & Folders
• list nested directories with ls -FR
• use the finder to see the folders you just created
• good names for files and directories do not use blank spaces
  • Read File Naming Best Practices
• creating a text file with nano
• using the nano text editor
• homework challenge: creating a text file with touch
• file extensions
• moving files and directories with mv
• copying files and directories with cp
• removing files with rm and directories with rm -r
• wildcards * and ?
• Challenge
• Homework activities

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Day 2

Pipes and filters (35 min)

• SWC lesson

IN-CLASS ACTIVITIES

A) Go into teams of 2 or 3 people. Find a name for your team and write it down in the etherpad along with the names of the team members. Take 5-7 min to do so.

B) Read https://swcarpentry.github.io/shell-novice/04-pipefilter/index.html and run along the example code on the terminal (as well as the exercises!). Email the code to your instructor once you are done. You can email the code as a .txt file or directly on the body of the email.

C) As you read, discuss with your team and answer:

1) what does the command wc do?

2) what do the options -l, -m, and -w from the wc command do?

3) How do you escape a waiting command?

4) What symbol do you use to redirect output to a file instead of printing it to the screen?

5) What does the cat command do?

6) What does sort -n do?

7) What command can you use to confirm that a file exists?

8) What is the main difference between the cat and less commands?

9) What happens if you redirect the output of a command operating on a file to the same file?

10) What does the symbol >> do?

11) What is the main difference between the commands head and tail?

12) What symbol do you use to pass the output of a command as input of the next command?

13) What is a pipeline?

14) What is the main difference between redirecting and piping an output?

15) What does the uniq command do?