Guide: Initial git setup and mycode repo

Written by Maria Paula Hernandez and Liana Keesing, incorporating work of past TAs

In CS107e, we distribute course materials as git repos and you will use git to access, manage, and submit your work. These repositories are hosted on GitHub. This guides walks you through the steps to do the initial setup of the mycode repo. The mycode repo is where you will manage all of your cs107e code.

Note You should only need to follow the steps in guide once at the beginning of the course (unless you have to redo your setup for some reason). As always, be sure to ask for help if you run into any snags!


Each student has their own mycode repo, which manages all of the code for the coures assignments and labs.

We create a personal repository for each student on GitHub. This repo will be named[YOUR-GITHUB-USERNAME], where [YOUR-GITHUB-USERNAME] is replaced with your actual github username.

Your personal repository that resides on GitHub is your remote mycode repo. After we have set up your remote repo, you will connect it to a local mycode repo on your on your laptop. You will work on your code in the local repo and use git commands to exchange code between the local and remote repos.

Follow the steps below to set up your mycode repo.

Step 1: Accept GitHub invitations

You should have received two email invitations from GitHub: an invitation for read-only access to the code mirror repo and another invitation for read-write access to your personal repo winter24-[YOUR-GITHUB-USERNAME]. Once you receive and accept both invitations, you're ready to proceed.

Step 2: Create SSH key and add to GitHub account

To streamline interacting with GitHub, you'll need to add an SSH key on your GitHub account. An SSH key authenticates your identity. To create an SSH key, enter the following command in your shell:

$ ssh-keygen -t rsa -b 4096 -C "<your_email>"

After you press enter, you'll be prompted to choose a filename in which to save your key. Accept the default by pressing enter. Next, you'll be prompted to enter a passphrase for a key. If you want no passphrase, press enter. Otherwise, enter your passphrase. If you choose to add a passphrase, you must enter that passphrase each time you push to or pull from GitHub .

Check: confirm the key was created

Confirm the key has been created by looking for the key files in your .ssh directory:

$ ls ~/.ssh/

You should see two files: id_rsa and SSH uses public-key cryptography, which requires a private key and a public key. id_rsa is your private key and should never be shared. is your public key and can be shared to validate your identity.

Follow these instructions from Github to add your SSH key to your GitHub account.

Step 3: Configure git identity

Use the commands below to configure your git identity so that your git actions are properly recorded. Be sure to replace Pat Hanrahan and with your own name and address. The last command just specifies that you want your repositories to merge on a git pull by default.

$ git config --global "Pat Hanrahan"
$ git config --global
$ git config --global pull.rebase false

Check: confirm your git identity

$ git config --get-regexp user Pat Hanrahan

Step 4: Create cs107e_home directory

Make a new directory named cs107e_home to store course material within your home directory. The tilde character ~ is shorthand for the user's home directory.

$ mkdir ~/cs107e_home

Note: If you're using WSL, now is a good time to open File Explorer on your cs107e_home directory and "Pin to Quick Access" to add it the sidebar for future use. See accessing WSL files from Windows.

Step 5: Make local clone

Note In the commands below, replace any reference to [YOUR-GITHUB-USERNAME] with your actual GitHub username.

In your browser, visit the page[YOUR-GITHUB-USERNAME] to see the contents of your remote repo. It should have only a single file:, which lists the name of your repo and nothing more.

Make a local clone of your repo. This is a copy of the remote repo that lives locally on your computer. You are doing to store your repo in the parent directory cs107e_home that you just made. Execute the following terminal commands to make your local mycode repo.

$ cd ~/cs107e_home
$ git clone[YOUR-GITHUB-USERNAME].git mycode

Change to your repo and use ls confirm the files match those you see when browsing your remote repo on GitHub.

$ cd mycode
$ ls
$ cat

You'll notice that the command cat will just print the contents of a file to your terminal. This is a useful command that you'll use again!

Step 6: Create dev branch (local and remote)

The master branch in your repo is "write-protected," which means that you will not be able to directly modify this branch on GitHub. Instead, you'll do your work on a separate dev branch. To create this branch, change to your repo and execute the following commands:

$ cd ~/cs107e_home/mycode
$ git branch
$ git checkout -b dev
$ git branch

When you execute the first git branch command, notice how there is only a single branch listed: master and there is an asterisk next to master. This asterisk identifies which is the currently checked out branch. When you run the second git branch command, you should have two branches (master and dev) and the asterisk is now next to dev.

The new dev branch you created only exists in your local repo; next you will connect it to a new remote branch of the same name. Use git branch to confirm that you are on the dev branch and execute the following command:

$ git push --set-upstream origin dev

If you return to your GitHub repo in your browser, you should now find a dev branch in the branches dropdown menu.

Step 7: Add code-mirror remote

Now you will configure your local repo to have an additional remote connection to the code mirror repo. The code-mirror repo is where we place the starter code for labs and assignments. Execute the following commands to add the remote code-mirror repository for which you ealier accepted the invitation.

$ git remote -v
$ git remote add code-mirror
$ git remote -v

When executing the first git remote -v command, you should have only a single remote: origin. origin is a shorthand way of referring to your remote repo on GitHub. The git remote add command adds a second remote. This second remote is code-mirror, which is a shorthand way of referring to the code mirror repo on GitHub. The second git remote -v should show you both remotes: origin and code-mirror and the URLs that they represent.

Before we move on, we actually need to pull some code from the code-mirror remote repo. If you look at (which we call code-mirror), you'll see that it contains a folder called cs107e. That folder, if you look inside, contains a number of folders (like bin, include, and src) filled with files. Those files will serve as the base code for CS107e, and the code you write will sometimes reference those files (for example, all the .h files you'll reference in this class are located in the include folder). To update your local mycode repo to include the cs107e folder, use the following command:

$ git pull code-mirror master

Check: confirm the cs107e folder is on your local machine

$ cd ~/cs107e_home/mycode
$ ls cs107e
bin  include  lib  sample_build  src

You should now see a list of the folders inside the cs107e folder.

Step 8: Edit shell configuration file

While we now have the cs107e folder (filled with all of its goodies) safely tucked away in our mycode folder, we need to tell our shell environment that it exists so that we can reference it easily when we make our code later.

What does that mean? If we needed to, we could refer to the cs107e folder every time by its location: ~/cs107e_home/mycode/cs107e. But that's so long—and if I made my path any different than yours, then suddenly all of my code would break. So instead, we can use a nickname for the cs107e folder, since we're going to need to refer to it frequently.

When opening a new shell, the environment is initialized by reading a configuration file in your home directory. Editing the configuration file allows you to set the initial state of your shell to have this nickname. Here are the steps to do that:

  1. Determine the name of the configuration file for your shell. The name depends on which shell you are using. Use the command echo $SHELL to see your shell. Your shell is likely bash, although it might be zsh if using a more recent macOS.
     $ echo $SHELL

    If your shell is bash, the configuration file is named .bashrc. If your shell is zsh, the configuration file is named .zshrc. For any other shell, please ask a CA for help.

  2. Find out if you already have an existing configuration file or create it if needed. Change to your home directory and list the files. Filenames starting with a dot are hidden in a directory listing by default. Use the command ls -a to list all files, including hidden ones:
     $ cd ~
     $ ls -a
     .    .bash_history   .bashrc     cs107e_home     .python_history 
     ..   .bash_logout    .config     .profile        .viminfo

    (The filenames listed in your directory may be somewhat different, don't worry!) Look through list to see if there is already a configuration file for your shell. If not listed, use touch to create an empty file with the appropriate name:

     $ touch .bashrc
  3. Open the configuration file in a text editor and append the following two lines verbatim:
     export CS107E=~/cs107e_home/mycode/cs107e
     export PATH=$PATH:$CS107E/bin

    The first line sets the environment variable CS107E to the path to where the class files are stored. The second line adds our bin subdirectory to your executable path.

  4. Use the source command to read the updated configuration file into your current shell:
     $ source ~/.bashrc

Check: confirm current shell is properly configured

$ echo $CS107E
$ ls $CS107E/lib/libmango.a
$ which

The configuration file is persistent and should be automatically read when creating a new shell in the future.

Check: confirm shell configuration is persistent and future shells properly configured

Close your current shell and open a new one. Repeat the check step above in the new shell and confirm the new shell is also properly configured.

If you confirm your configuration is persistent, skip the step below. If it is not persistent and you are using bash and the macOS Terminal, use the additional customization below to add persistence.

  1. (only if needed) Find the file named .bash_profile in your home directory. If no such file exists, use the touch command to create an empty file with that name. Open that file in a text editor and append the following line verbatim:
     source ~/.bashrc

Repeat the previous check step with a new shell to confirm your configuration is now persistent.

Step 9: Celebrate! You've set up your code base! 🎉

Yay! That was a lot of steps you just did! Once you've finished this, the next step is to put in some work to understand just how to use this awesome setup you've created. To do that, check out the CS107E Github workflow guide.