Why Systems?

3. Why Systems?#

3.1. 5 minutes#

3.2. Questions?#

Issues, Pull requests, Prepare, Practice, Review, Lab…

3.3. Working offline#

Today more clear motivation for each thing we do and more context.

Today we will learn to work with GitHub offline, this requires understanding some about file systems and how content is organized on computers.

We will learn:

  • relative and absolute paths

  • basic bash commands for navigating the file system

  • authenticating to GitHub on a terminal

  • how to clone a repo

  • how fetch and checkout work

3.4. Let’s get organized#

For class you should have a folder on your computer where you will keep all of your materials.

We will start using the terminal today, by getting all set up.

Open a terminal window. I am going to use bash commands

  • if you are on mac, your default shell is zsh which is mostly the same as bash for casual use. you can switch to bash to make your output more like mine using the command bash if you want, but it is not required.

  • if you are on windows, your GitBash terminal will be the least setup work to use bash (preferred)

  • if you have WSL (if you do not, no need to worry) you should be able to set your linux shell to bash (I believe it already is set to bash)

If you use pwd you can see your current path

pwd


Users/ayman

It outputs the absolute path of the location that I was at.

we start at home ~

We can change directory with cd

if we use cd without a path, it goes back to home cd ~ would do the same

We can mak a new directory with mkdir

What you want to have is a folder for class (mine is systems) in a place you can find it

You might:

  • make a systems folder in your Documents folder

  • make an inclass folder in the CSC311 folder you already made

  • use the CSC311 folder as your in class working space

If I run the following commands, what do I expect as the output?

cd 
pwd

  • [ ] cannot tell, do not know where you started

  • [x] /c/Users/ayman

  • [ ] /c/Users/ayman/Documents

  • [ ] the same as whereever you were before

When you use pwd what type of path does it return?

  • [x] absolute

  • [ ] relative

The first slash / represents the /(root) directory, which is the starting place for the search

But what does it mean when a path starts with . or ..?

To go back one step in the path, (one level up in the tree) we use cd ..

cd ..

.. is a special file that points to a specific relative path, of one level up. (In other words, parent folder/directory)

use pwd , cd and pwd to illustrate what “one level up” means

Did you notice the dieffernce?

cds Documents/

bash: cds: command not found

notice that command not found is the error when there is a typo

cd Documents/
pwd

/c/Users/ayman/Documents

mkdir systems

/c/Users/ayman/Documents/systems

cd ..
pwd

/c/Users/ayman/Documents/

If we give no path to cd it brings us to home.

cd 
pwd

/c/Users/ayman

Then we can go back.

cd Documents/systems/
pwd

/c/Users/ayman/Documents/systems

Do you have any content in the folder?

ls

Could be empty of if you had created it before you would see the content you had in it

We can use two levels up at once like this:

cd ../../
pwd

/c/Users/ayman

cd Documents/systems/

We can the tab to complete once we have a unique set of characters. If what we have is not unique enoguh yet, bash will do nothing when you press tab once, but if you press it multiple tiems it will show you the options:

cd Do

Press tab twice. The consol outputs:

Documents/ Downloads/ 
cd Do

cd Doc

Press tab… The consol auto completes the path

cd Documents/

What character is always at the start of absolute paths?

  • [ ] :

  • [x] /

  • [ ] *

  • [ ] ]

What type of path is ../../Downloads ?

  • [ ] absolute

  • [x] relative

3.5. A toy repo for in class#

this repo will be for in class work, you will not get feedback inside of it, unless you ask, but you will answer questions in your kwl repo about what we do in this repo sometimes

only work in this repo during class time or making up class, unless specifically instructed to

Preferred:

  1. view the template

  2. click the green “use this template” button in the top right

  3. make compsys-progtools the owner

  4. set the name to gh-inclass-<your gh username> replacing the <> part with your actual name

Backup: accept the assignment

3.6. Authenticating with GitHub#

We have two choices to Download a repository:

  1. clone to maintain a link using git

  2. download zip to not have to use git, but have no link

we want option 1 beacuse we are learning git

For a public repo, it won’t matter, you can use any way to download it that you wuold like, but for a private repo, we need to be authenticated.

3.6.1. Authenticating with GitHub#

There are many ways to authenticate securely with GitHub and other git clients. We’re going to use easier ones for today, but we’ll come back to the third, which is a bit more secure and is a more general type of authentication.

  1. ssh keys (we will do this later)

  2. gh CLI with gh auth login

we will do opiton 2 for today

3.6.1.1. GitBash (windows mostly)#

  • git clone and paste your URL from GitHub

  • then follow the prompts, choosing to authenticate in Browser.

3.6.1.2. Native terminal ( MacOS X/Linux/WSL)#

  • GitHub CLI: enter gh auth login and follow the prompts.

  • then git clone and paste your URL from github

3.6.1.3. If nothing else works#

Create a personal access token. This is a special one time password that you can use like a password, but it is limited in scope and will expire (as long as you choose settings well).

Then proceed to the clone step. You may need to configure an identity later with git config

3.6.2. Cloning a repository#

We will create a local copy by cloning

Type pwd first to make sure you’re in the Systems folder

git clone https://github.com/compsys-progtools/gh-inclass-AymanBx

Cloning into 'gh-inclass-AymanBx`...
remote: Enumerating objects: 8, done.
remote: Counting objects: 100% (8/8), done.
remote: Compressing objects: 100% (4/4), done.
remote: Total 8 (delta 0), reused 4 (delta 0), pack-reused 0
Receiving objects: 100% (8/8), done.

Confirm it worked with:

ls

gh-inclass-AymanBx

We see the new folder that matches our repo name

3.7. What is in a repo?#

We can enter that folder

cd gh-inclass-AymanBx/

When we compare the local directory to GitHub

ls

Notice that the .github/workflows that we see on GitHub is missing, that is because it is hidden. All file names that start with . are hidden.

We can actually see the rest of the files or folders with the -a for all option or flag. Options are how we can pass non required parameters to command line programs.

ls -a

.		.git		
..		.github

We also see some special “files”, . the current location and .. up one directory

3.8. How do I know what git knows?#

git status is your friend.

git status

On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean

this command compares your working directory (what you can see with ls -a and all subfolders except the .git directorty) to the current state of your .git directory (more on that later …).

3.9. Making a branch with GitHub and working offline#

First on an issue, create a branch using the link in the development section of the right side panel. See the github docs for how to do that.

“create an about file”

Then it gives you two steps to do. We are going to do them one at a time so we can see better what they each do.

First we will update the .git directory without changing the working directory using git fetch. We have to tell git fetch where to get the data from, we do that using a name of a remote.

git fetch origin

From https://github.com/compsys-progtools/gh-inclass-AymanBx
 * [new branch]      1-create-an-about-file -> origin/1-create-an-about-file

We can look at the repo to see what has changed.

git status

On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean

This says nothing, because remember git status tells us the relationship between our working directory and the .git repo.

Next, we switch to that branch.

git checkout 1-create-an-about-file

branch '1-create-an-about-file' set up to track 'origin/1-create-an-about-file'.
Switched to a new branch '1-create-an-about-file'

and verify what happened

git status

On branch 1-create-an-about-file
Your branch is up to date with 'origin/1-create-an-about-file'.

nothing to commit, working tree clean

Run your Experience Badge (inclass) action. Github how to

  1. Go to the Actions tab

  2. Click the Experience Badge (inclass) on the left hand side

  3. Click the run workflow button on the right

  4. Click the run workflow button in the popup

3.10. Prepare for next class#

  1. Find the glossary page for the course website, link it below. Review the terms for the next class: shell, terminal, bash, git, zsh, powershell, GitHub. Make a diagram using mermaid to highlight how these terms relate to one another. Put this in a file called terminal-vocab.md on a branch linked to this issue.

  2. Check your kwl repo before class and see if you have recieved feedback, reply or merge accordingly.

3.11. Example#

Example “venn diagram “ with mermaid subgraphs

flowchart subgraph Browsers subgraph Safari end subgraph Chromium based gg[Google Chrome] me[Microsoft Edge] end end

3.12. Badges#

Any steps in a badge marked lab are steps that we are going to focus in on during the next lab time. Remember the goal of lab is to help you complete the work, not add additional work. The lab checkout will include some other tasks and then we will encourage you to work on this badge while we are there to help. Lab checkouts are checked only for completion though, not correctness, so steps of activities that we want you to really think about and revise if incorrect will be in a practice or review badge.

  1. Read the notes. If you have any questions, post an issue on the course website repo.

  2. Using your terminal, download your KWL repo. Include the command used in your badge PR.

  3. Try using setting up git using your favorite IDE or GitHub Desktop. Make a file gitoffline.md and include some notes of how it went. Was it hard? easy? what did you figure out or get stuck on? Is the terminology consistent or does it use different terms?

  4. lab Explore the difference between git add and git commit: try committing and pushing without adding, then add and push without committing. Describe what happens in each case in a file called gitcommit.md. Compare what happens based on what you can see on GitHub and what you can see with git status.

Any steps in a badge marked lab are steps that we are going to focus in on during lab time. Remember the goal of lab is to help you complete the work, not add additional work. The lab checkout will include some other tasks and then we will encourage you to work on this badge while we are there to help. Lab checkouts are checked only for completion though, not correctness, so steps of activities that we want you to really think about and revise if incorrect will be in a practice or review badge.

  1. Read the notes. If you have any questions, post an issue on the course website repo.

  2. Using your terminal, download your KWL repo. Include the command used in your badge PR comment.

  3. Try using setting up git using your favorite IDE or GitHub Desktop. Make a file gitoffline.md and include some notes of how it went. Was it hard? easy? what did you figure out or get stuck on? Is the terminology consistent or does it use different terms?

  4. lab Explore the difference between git add and git commit: try committing and pushing without adding, then add and push without committing. Describe what happens in each case in a file called gitcommit_tips.md. Compare what happens based on what you can see on GitHub and what you can see with git status. Write a scenario with examples of how a person might make mistakes with git add and commit and what to look for to get unstuck.

3.13. Questions after class#

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