script.sh

#!/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