Before the lab

Before every lab in this course, you will be given tasks to complete. These will generally be easy tasks like watching videos, but you need to complete them in order to keep up with the class.

Command Line Familiarity Check

1. In an FCS linux lab (remote or locally) log in, and open a terminal.

2. Make a directory

3. Create a file in that directory using one of the available text editors

4. Now clean up, removing the file and the directory.

If any of this was new to you, then please take the time to go through parts 1 to 5 of the Learning the Shell Tutorial.

Read the course syllabus.

The Course Syllabus is available on line. Please read it, and bring any questions you have about it to the first lab.

Background Reading

For every lab there will be some related reading. I'll point these out as we go through the lab, but I'll also collect them at the start of the lab in case you want to get a head start (or refer back to them later).

• Git Basics from Pro Git
• Basic Shell Background

About the course

1. What's similar to other CS courses you've taken?

2. What's different?

3. Key point, how are labs evaluated?

Getting started with racket

1. Open a terminal.

2. Make a directory called cs2613 that will keep all of your work (note that case and spaces matter in Linux and this is not the same as CS2613 or CS 2613. For the rest of this course we will assume it is directly under your home directory. The shortcut ~/cs2613 will refer to this directory in the lab texts and in the shell.

Hello Racket World

• Open a terminal

• Make a directory ~/cs2613/labs/L01 (if it does not already exist) and change there with cd

• Save the following code to ~/cs2613/labs/L01/hello.rkt

#lang htdp/bsl
"hello world"
(* 6 7)

Command Line

• run the program with

    $ racket hello.rkt
  

• What is the difference between the first and second line of output?

• compile the program

    $ raco make hello.rkt
  

• run the program again

    $ racket hello.rkt
  

• can you tell any difference? (hint, consider the "time" command).

DrRacket: A Racket Specific IDE

• Start DrRacket from the activities menu

• Referring to the DrRacket documentation as needed, open and run the hello.rkt program from the previous part.

• What is the meaning of the first line of the file?

Setting up a git repo

1. Change to ~/cs2613. This directory should have one subdirectory called labs, which has the results of our experiments with racket.

2. Create the git repository

    $ git init -b main
   

   Git will reply with something like

    Initialized empty Git repository in /home1/ugrads/$username/cs2613/.git/
   

   You’ve now initialized the working directory — you may notice a new directory created, named ".git". You should mentally replace "$username" with whatever the login name is that you use to log into the FCS linux machines.

3. Read the git-quickref page, and follow the initial configuration steps there.

   • note that the "--wait" option for gedit is important here.

4. Next, tell Git to take a snapshot of the contents of all files under the labs, with git add:

   $ git add labs
   

This snapshot is now stored in a temporary staging area which Git calls the "index". You can permanently store the contents of the index in the repository with git commit:

   $ git commit

This will open and editor and prompt you for a commit message. Enter one and exit the editor. You’ve now stored the first version of your project in Git. See §5.2 of Pro Git for some hints about writing good commit messages. As mentioned in the class git policy, you will be marked on your commit messages, so you may as well get started with good habits.

Pushing to a central repo

Since we are using the FCS git repositories there is an existing repository for all students who registered early enough. If it turns out there is no repository for you, you may need to do the last step later.

• First add the remote. This something like a nickname for the URL where the repo will be stored.

    $ git remote add origin https://$username@vcs.cs.unb.ca/git/cs2613-$username
  

  origin is the default name for a remote, but we could have used a different name here. Replace $username with your FCS Linux account name.

• Now upload your local copy of the repo.

    $ git push --all origin
  

  you should see something like

            Counting objects: 388, done.
            Delta compression using up to 8 threads.
            Compressing objects: 100% (350/350), done.
            Writing objects: 100% (388/388), 71.63 KiB | 0 bytes/s, done.
            Total 388 (delta 223), reused 59 (delta 33)
            To https://$username@vcs.cs.unb.ca/git/cs2613-$username
               e7e5311..f1ae959  main -> main
  

Git Tutorial Continued

Making Changes in git

Change to the root of your git repository (~/cs2613). Start by finding the right files to edit with

$ git grep hello

git grep is a very useful (and fast!) tool to find occurrences of strings in your git repository. Notice in the output there are some Binary files created by racket; we will clean those up later.

Edit the non-binary (source code) file, and change the output message.

Use git add to stage your changes:

$ git add file1 

(replace file1 with the actual file you modified). You are now ready to commit. You can see what is about to be committed using git diff with the --cached option:

$ git diff --cached

or $ git diff --cached --stat

To undo the effect of a git add command, run git reset.

(Without --cached, git diff will show you any changes that you’ve made but not yet added to the index.) You can also get a brief summary of the situation with git status:

$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#       modified:   file1
#       modified:   file2
#       modified:   file3
#

If you need to make any further adjustments, do so now, and then add any newly modified content to the index. Finally, commit your changes with:

$ git commit

This will again prompt you for a message describing the change, and then record a new version of the project.

Alternatively, instead of running git add beforehand, you can use

$ git commit -a

which will automatically notice any modified (but not new) files, add them to the index, and commit, all in one step. Keep in mind that you will be marked on the logical structure of your git commits, so you are better off using git add to explicitely choose what changes to commit.

Cleaning up generated files

A common phenomenon in software development is the existence of generated files. These files are created by some tool, typically based on some source files. In general it is a bad idea to track generated files in version control because they introduce spurious changes into history. We'll look at this more later, but for now let's try to clean up. We can often find what files are generated by re-running the build process. In our case

$ cd ~/cs2613/labs/L01
$ raco make hello.rkt

To find out what changed, run

$ git diff --stat

All going well, you will two modified files. You can delete them using git rm. As with with other changes, you can preview your changes with git diff and git status.

When you are satisfied with the changes, run git commit.

Before next lab