Programming Course Homework 1

Hi folks! Ok, here is your first homework.

Logistics

• You have time until March 3rd 2026
• You must do the homework in teams of 2 or 3 students

Submitting via Pull Request (PR)

Now you are real github pros 👷🏻‍♀️👷🏾‍♂️👩🏽‍💻👨🏻‍💻 so you will submit this via pull request. Let me take you through it.

Setting up your copy of this repo: Create a Fork

1. Towards the top right of this page, search for the Fork button.
2. Click it. This will setup a copy of this repo on your own user space. Wait a moment. We will end up on your github user space, at YOUR_USERNAME/introprogHW. Stay there.
3. Let's get this repo onto your computer. Click the green button (<> Code) and copy the Https URL (i.e. something like https://github.com/YOUR_USERNAME/introprogHW.git)
4. open the terminal on your computer. where you type bash commands.
5. choose a suitable location for this homework. I'll assume you choose to put it into ~/CCA-computing. execute this:

   mkdir -p ~/CCA-computing  # make that directory
   cd ~/CCA-computing # go there
   git clone https://github.com/YOUR_USERNAME/introprogHW.git 

after this step you will have the content of this repo on your computer at ~/CCA-computing/introprogHW. Cool, right?

Notice that the location of this repo on your computer and where you will download data in the below exercise is different

Do The Job 💪🏽

• Ok great, good to go.

• Start the VSCode editor and open the local repo. If you were following along, that means opening ~/CCA-computing/introprogHW in VSCode (do that from withing VSCode, not on the command line)

• Open the script.sh file. You need to fill in some bits and pieces, and run it frequently to check that it does what you want.

• Remember that if there is a script run.sh located in a certain directory dir, you can execute it via ./dir/run.sh. If you are inside dir, that of course becomes ./run.sh. (the leading . is important!)

• I would recommend that you open the terminal inside VScode (in top menu, Terminal > New Terminal), edit the script.sh file, and then repeatedly execute it in the terminal.

• Like, if you do that now, you will see this:

  welcome to this homework script!
  ================================
  
  You should run this until you see:
  correct! :-)
  
  as the final output in your terminal.
  
  How do you run a script? Just do ./script.sh on your command line!
  
  START HOMEWORK SCRIPT
  ---------------------
  
  student 1
  student 2
  directory created successfully
  /opt/homebrew/bin/wget
  
  File not found!
  will download now to current directory now\n
  
  --2026-02-24 12:29:49--  https://raw.githubusercontent.com/sidooms/MovieTweetings/44c525d0c766944910686c60697203cda39305d6/snapshots/10K/movies.dat
  Resolving raw.githubusercontent.com (raw.githubusercontent.com)... 185.199.108.133, 185.199.111.133, 185.199.109.133, ...
  Connecting to raw.githubusercontent.com (raw.githubusercontent.com)|185.199.108.133|:443... connected.
  HTTP request sent, awaiting response... 200 OK
  Length: 162905 (159K) [text/plain]
  Saving to: ‘./movies.dat’
  
  ./movies.dat         100%[======================>] 159.09K  --.-KB/s    in 0.02s   
  
  2026-02-24 12:29:49 (7.67 MB/s) - ‘./movies.dat’ saved [162905/162905]
  
  File first4.txt not found! Error.

• ... informing us, the currently this script is producing the wrong result 😉. Over to you now!

Submit your PR

1. After you are happy with your script, time to submit it.
2. prepare a commit of your script to the local repository.
3. git add script.sh, git commit -m 'your message', just like you know how to do. 😀
4. No need to add a remote, the initial git clone command took care of that.
5. So, only thing left is to git push. Do it! 🚀
6. Final step: back on https://github.com/YOUR_USERNAME/introprogHW, click on new pull request on the top right of the code box. Looks like this:
7. After you created the PR, you can check whether my test script thinks you got the correct result but looking out for the green check mark ✅
8. If you made a mistake you'll see a red cross instead ❌. you can look at the output of the testing server, fix your mistake (if any), prepare a new commit, and push again, exactly like before. For me it's failing right now:

Tasks from script

Below is the content of your script. No need to do anything with that, just putting it here in case you prefer reading through it before doing anything. You will see I am only asking for very basic stuff.

#!/bin/bash
set -e


# Hi! Please do not modify the above lines.
# 
echo "welcome to this homework script!"
echo "================================"
echo ""
echo "You should run this until you see:"
echo "correct! :-)"
echo ""
echo "as the final output in your terminal."
echo ""
echo "How do you run a script? Just do ./script.sh on your command line!"
echo ""
echo "START HOMEWORK SCRIPT"
echo "---------------------"
echo ""


# 0. Tell me who worked on this together
echo "student 1"   # please fill in names here
echo "student 2"

# here is a list of tasks for you.
# whenever a line says "don't touch" then you are not supposed to touch what comes below.
# all lines where you need to take action are numbered.

# 1. Go to your home directory:


# 2. from your home, creating a directory structure: new folder `programming-hw`, and inside that folder create folder `hw1`

# 3. go into that new directory, i.e. into ~/programming-hw/hw1

# checking the folder exists now
# don't touch
[ -d ~/programming-hw/hw1 ] && echo "directory created successfully" || exit 1

# download with wget if file does not exist yet
# if wget does not work for you, manually download from the below URL and place into `~/programming-hw/hw1` as `movies.dat`
# first let me check whether you have wget installed and install it otherwise for you:
# don't touch
command -v wget || { [[ "$OSTYPE" == "darwin"* ]] && brew install wget || sudo apt-get install -y wget; }
echo ""
# don't touch
if [ ! -f  movies.dat ]; then
    echo "File not found!"
    echo "will download now to current directory now\n"
    echo ""
    wget https://raw.githubusercontent.com/sidooms/MovieTweetings/44c525d0c766944910686c60697203cda39305d6/snapshots/10K/movies.dat -O./movies.dat
fi

# check file exists now
# don't touch
if [ ! -f  movies.dat ]; then
    echo "File not found! Error."
    exit 1
fi

# 4. look at first 4 rows of downloaded data in `movies.dat`. look at this output and try to understand how it is structured. the file ending is `dat`. however, how could you also denominate such a file?


# 5. look at first 4 rows of downloaded data in `movies.dat` redirect to a file called `first4.txt`


# don't touch
if [ ! -f  first4.txt ]; then
    echo "File first4.txt not found! Error."
    exit 1
fi
# check whether file is correct:
res=$(awk -F '::' '{print $1}' first4.txt )
echo ""
[ "$res" = "$(printf '0002844\n0007264\n0008133\n0012349')" ] && echo "first4.txt correct" || exit 1
echo ""

# actual analysis task: A pipeline
# we want to know how many genres each movie is classified into
# `genre1|genre2` means it's in genre1 and genre2: we would count `2` for such an entry
# the end product of our pipeline is a contingency table, informing us
# about how many movies are part of how many genres. it would look similar to
#  2 0
#  5 1
# 10 2
# meaning we have 2 movies without any genre, 5 movies with 1, 10 with 2, etc
 
# I want you to construct a pipeline. let's build it up from the start

# 6. use the `awk` command to separt each row at the `::` delimters
# fill in for _filename_ the correct file you want to operate on. 
# then remove the # character from the start of the line and look at the result

# awk -F '::' '{print $3}' _filename_

# 7. observe that the `{print $3}` part prints the third field. that looks like: genre1|genre2
# that is, there is *another* separator in this column, `|`. Let's separate again. copy your command from above and 
# add a pipe as follows. here, the second statement will split at `|` and print into *how many parts* it has split.
# i.e. it will tell us *how many genres* that movie belonged to. No need to understand the `awk` part.
# again, remove the # below, fill in for _filename_ and run

# awk -F '::' '{print $3}' _filename_ | awk '{print split($0, a, "\\|")}'


# 8. finish the pipeline by adding 2 commands, exactly like in class, that will produce a contingency table
# we want to know how many movies belong to 0,1,2,... etc genres. 

# awk -F '::' '{print $3}' _filename_ | awk '{print split($0, a, "\\|")}' | sort | uniq -c

# 9. redirect (>) the output of your pipeline to a file `outtable.txt` in the current directory


# dont touch
echo ""   # leave this untouched
echo "here is my table:"   # this as well

# 10. Print your table to screen



#### End of your tasks
# please do not modify the below lines
echo ""
echo ""
echo "checking results...."
res=$(tail -n 1 outtable.txt | awk -F ' ' '{print $1}')
if [ ${res} == 5 ] 
then
    echo "correct! :-)"
    exit 0
else
    echo ""
    echo "wrong result :-("
    exit 1
fi