Description

COMP2113 Programming Technologies
Module 2 Checkpoint Exercise

Instructions:
For each single question or each group of questions in the Checkpoint exercise, please type your answer right after the question in this Word document. Please refer to the example below.
Checkpoint 0:

Checkpoint 2.1 (Please answer in this document and submit to Moodle)
What is the output of the following shell script? Please explain your answer.
#!/bin/bash a=100 b=99 if [ $a > $b ] then echo “$a is larger” else echo “$b is larger” fi if [ $a -gt $b ] then echo “$a is larger” else echo “$b is larger” fi

Solution
99 is larger
100 is larger
We get this output because 100 is sorted before 99 so $a /> $b evaluates to False, hence the commands in the else clause are executed (1 is sorted before a 9). Whereas the -gt command compares the numeric magnitude of $a and $b, and since 100 is larger in magnitude than 99 we get the result in the second line of the output.
Checkpoint 2.2: Shell Script to mark all assignments (Please submit and evaluate your answer in VPL) Let’s upload the module2 files to the Linux server and browse to Assignments/
$ cd Module2/
$ cd Assignments/
$ ls
2012111111 2012222222 2012333333 input.txt correct.txt mark.sh

Let’s write a script to mark all the assignments in a class!
2. In this example, we have three students with UID 2012111111, 2012222222 and 2012333333.
3. The test cases input.txt and correct.txt are located in the Assignments directory.
4. The shell script mark.sh is under the Assignments directory, to be updated by you.
5. Evaluate your answer on Moodle. Test case files and student submissions are included in the evaluation environment. You only need to submit your updated mark.sh.
6. When locating a file or directory in mark.sh, use the relative path instead of the full path.

Consider the unfinished shell script mark.sh
#!/bin/bash
allStudents= Q1
for student in $allStudents
do
if Q2
then
cd $student
if Q3
then
g++ assign.cpp -o assign.o 2>error.txt
if Q4
then
./assign.o < ../input.txt > output.txt result=`diff output.txt ../correct.txt`
if Q5
then
echo “$student: Wrong answer.” else echo “$student: Correct!” fi else echo “$student: Cannot be compiled.” fi fi cd ..
fi done

Question1:
• What should be the code in Q1? (Reminder, spacing is critical!)
• Hints: First we need to get the names of the files and directories under our current directory, what is the command to do this? How we can execute shell command in shell script and store the result in the variable allStudents?

Question 2:
• However, the command in Q1 also returns files under the Assignments directory, such as the test case files input.txt and correct.txt, as well as the shell script mark.sh.
• We need an if statement, what should be the condition in Q2?
• Hints: How can we check if $student is a directory?

Question 3:
• After we have identified the student’s directories and browse into them one by one using the cd $student command, we need to check if the student has submitted assign.cpp or not.
• What is the condition to be filled in Q3?

Question 4:
• If the student has submitted assign.cpp, we then need to compile the assign.cpp, and report on screen if it cannot be compiled.
• We need to check if assign.cpp can be compiled or not.
• What is the condition to be filled in Q4?
• Hints: if the compilation is successful, what file will be created after executing the line
g++ assign.cpp -o assign.o 2> error.txt ?

Question 5:
• If the student has submitted assign.cpp, and assign.cpp can be compiled, we then need to check if the output file output.txt is the same as the test case correct.txt or not.
• The result=`diff output.txt ../correct.txt` command will store some value in the variable
$result if output.txt is different from correct.txt.
• Therefore, if the length of the string $result is NOT EQUAL to 0, then there is something output by the diff command, that means assign.o returns wrong answer.
• What is the condition to be filled in Q5?

Upload your mark.sh to the Moodle page “Checkpoint 2.2: Shell Script to mark all assignments” under Module 2 and evaluate it.

You can refer to “Quick VPL Guide” on Moodle if you don’t know how to use the evaluation system.

Checkpoint 2.3: Shell Script to analyze web log (Please submit and evaluate your answer in VPL)
Suppose the web server of your company website that produces a log file which captures every page access in the following format:
ip_address date_YYYY/mm/dd time_HH:MM:SS page_accessed Here is a sample content of such file:
192.168.83.173 2014-09-04 10:05:17 /products.html
192.168.130.175 2014-09-04 10:09:13 /products/296.html
192.168.130.175 2014-09-04 10:25:01 /index.html 192.168.138.244 2014-09-04 10:29:37 /products.html …

You are asked to write a shell script, getProductAccess.sh, which captures the product pages under /products/ accessed by each IP address. The script takes one command line argument, which is the filename of a log file. It will read the content of the log file specified, find and print the product pages each IP address accessed. The output should be sorted by IP address and then by the product page.
• Sorting is done alphabetically, ascendingly for both IP address and product page, i.e., 192.168.0.11 will be ordered before 192.168.0.2.
• Only pages starting with /products/ should be printed.
• You can assume that the input file will strictly follow the above format. I.e.:
o The values will not consist of spaces or tabs.
• The script does not need to handle cases where the input file is empty, or if there is not enough argument specified.
Sample Run
Assume we have access-2014-09-04.log in the current directory, with the following content:
192.168.83.173 2014-09-04 10:05:17 /products.html
192.168.130.175 2014-09-04 10:09:13 /products/296.html
192.168.130.175 2014-09-04 10:25:01 /index.html
192.168.138.244 2014-09-04 10:29:37 /products.html
192.168.83.173 2014-09-04 11:00:00 /products/004.html
192.168.130.175 2014-09-04 11:01:20 /products/296.html
192.168.138.244 2014-09-04 11:22:49 /products.html
192.168.138.244 2014-09-04 11:23:00 /index.html
192.168.83.173 2014-09-04 12:19:55 /products/560.html
192.168.130.175 2014-09-04 12:24:24 /products/004.html

If we run the script like this:
$ ./getProductAccess.sh access-2014-09-04.log

The script will print:
192.168.130.175 /products/004.html
192.168.130.175 /products/296.html
192.168.83.173 /products/004.html
192.168.83.173 /products/560.html

Note that IP 192.168.130.175 accessed /products/296.html multiple times, but there should only be one corresponding line in the output.

Hints:

Upload your answer to the Moodle page “Checkpoint 2.3: Shell Script to analyze web” under Module 2 and evaluate it.

Checkpoint 2.4: Working with Git and GitHub
GitHub is an online service where you can store your projects and share your code with others easily. Later, we plan to request students commit their code and changes to GitHub mandatorily for the course project. Study the steps below to learn how to work with your local git repository with GitHub.
Create a GitHub account
1. Go to https://github.com/ to create a personal user account.
Create a personal access token
You should create a personal access token (PAT) to use in place of a password with the command line. When Git prompts you for your password, enter your personal access token instead of your password.
For example, you can do something like this with your token when working with GitHub:
$ git clone https://github.com/username/repo
Username: your_username Password: your_token

To create a personal access token, go to https://docs.github.com/en/github/authenticating-to-github/keeping-youraccount-and-data-secure/creating-a-personal-access-token and follow its procedures.
Note:
• In step 6, give your token a name whatever you like.
• In step 8, select all scopes and permissions if you are not sure what they are. (Less security but more convenience)
• Treat your token as like password and keep it secret!
Create a new repository on GitHub
Go to https://docs.github.com/en/get-started/quickstart/create-a-repo#create-a-repository and follow its procedure to create a repository in “GitHub.com”.
After the creation of a new repository, your browser will be directed to the main page of your new repository, which the URL has the formal of https://github.com/<username>/<repo>, where <username> is the name of your GitHub account and <repo> is the name of your new repository.
The screenshot below shows the main page of a new repository (Initialized with adding a README.md)

Push your files to GitHub
There are two main ways to connect your local git repository to GitHub.
Option 1: If you are starting from scratch and do not have a local repo, clone your GitHub repository to your local computer from the command line.
$ git clone https://github.com/username/repo
$ cd repo
• Replace the URL and directory name with your repository URL and name. Then work on the project and finally push it to GitHub
$ git add .
$ git commit -m “first commit”
$ git push

Option 2: If you have already created a repository locally, push your existing repository from the command line:
$ git remote add origin https://github.com/username/repo
$ git branch -M main
$ git push -u origin main
• Replace the URL with your repository URL.

Upon success, you will see your project files on GitHub.
Note: There is no need to submit anything for this checkpoint.
Checkpoint 2.5: GitHub Education
To join GitHub Education, you must have a personal GitHub account at https://github.com/ first.
Here are some steps to join the GitHub Education (For reference only):
1. Sign in to https://education.github.com and click “Get benefits”. In the application form, specify you are a student and creating an individual account.

2. Add your HKU email address and then click “Add”. A verification email will be sent to your HKU mailbox. Click the link in the email to verify your identity. Then click “Submit request”

3. You will receive your application result within certain days.

Note: There is no need to submit anything for this checkpoint.

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