Class 2A. Introduction to the File System, and the Terminal (Command line)

Class 2A. Introduction to the File System, and the Terminal (Command line)#

Lecture Outline#

1. Announcements (5 mins)

2. The File System (20 mins)

3. The Command Line (45 mins)

Part 1. Announcements (5 mins)#

Lab 1 will be due Wednesday January 18, 2023 at 6 PM

My office hours will be for 60 minutes after class on Mondays in EME 0050 and Fridays from 1-2 PM via Zoom. You can also ask for help anytime on Ed Discussion, as well as visiting any of the labs.

Lab sessions start this week, and will not be recorded.

Here are some keyboard shortcuts in VS Code to do some cool things:

Action	Shortcut on Mac	Shortcut on Windows
Insert additional cursor	Option + Click	Alt + Click
Insert cursor at end of each selected line	Shift + Option + I	Shift + Alt + I
Select all occurrences of current selection	Shift + Cmd + L	Shift + Ctrl + L
Select all occurrences of current word	Cmd + F2	Ctrl + F2
Add selection to next Find match	Cmd + D	Ctrl + D
Select current Line	Cmd + L	Ctrl + L

There are dozens more shortcuts, you can find the shortcuts here for:

Part 2. File System (30 mins)#

The file system organizes data on a device as a hierarchy of directories and files (like a tree). Each folder (AKA directory) has a name and can contain any number of files or subdirectories. Each file has a name. The user can change (navigate) directories in the hierarchy.

File System Root - Children and Parents#

The tree is rooted at, well, the root.

There is only one root of a directory hierarchy. Every item in the tree is either a file or a directory (AKA folder).
You can think of a directory as a container that may contains files and/or other directories.
Files on the other hand hold information (and cannot contain other files or directories) .

If directoryC is contained in directoryP, then directoryC is a child of directoryP and directoryP is said to be the parent to directoryC.

A directory may have many children, but can only have one parent.

Absolute versus Relative Path#

The root of the file system is the directory “/”
There is only one root of a directory hierarchy.
A path to a new location (from your current location) can be specified as an absolute path from the root (this will work no matter where we are in the file system):

Navigating relative paths#

. is the short-form for the current directory
.. signifies the parent directory (akin to pressing Cmnd + ↑ on a Mac, on Windows the shortcut is Alt+↑)
For example, to navigate (i.e. change directories) to the parent directory of the current directory, use the command: cd ..
Note that this command is dependant on your current directory (i.e. the folder you are currently in).
To print the current working directory, type in pwd

Absolute versus Relative Path Question#

Consider this directory hierarchy.

The user is currently in the directory level2
The level1 directory contains a file called test.txt.

Which of the following statements are TRUE?

A relative path to change to directory 301 is ..
Absolute path to test.txt is /Users/ivrbik/301/level1/test.txt
Relative path to test.txt is ../test.txt
Relative path to test.txt is different if user was currently in level3 directory.
There is only one root of the directory hierarchy.

Activity: Let’s try to re-create that directory and file structure#

You will need the following commands:

cd : change directory
pwd : print working directory
mkdir: make directory
ls: list directory contents
touch: create an empty file with a specific name
rm: Delete a file (if you make a mistake)
rm -r: Delete a directory (if you make a mistake)
code: edit the file in the VS Code editor

That’s it! See you Next Class!#

Additional Resources#

Supplementary video on absolute vs. relative paths#

IFrame(
    "https://www.youtube-nocookie.com/embed/sqX6hu7oEew", width="100%", height="500px"
)

Guide to the operating system for macOS users#

IFrame(
    "https://www.youtube-nocookie.com/embed/RX160bcMFuA", width="100%", height="500px"
)

Guide to the operating system for Windows 10 users#

IFrame(
    "https://www.youtube-nocookie.com/embed/egK5BKEn87c", width="100%", height="500px"
)