DM Revision

You need to list all files in the current directory including hidden files, sorted by size in human-readable format. Which command achieves this?

• ls -lSah

• ls -aSlh

• ls -lsha

• ls -lahS

Answer explanation

These commands will all produce the same result: listing all files in the current directory, including hidden files, sorted by size, in a human-readable format.

So, any of the provided options will work correctly. However, typically the order -aSlh (or any permutation of these options) is preferred for readability.

What will be the result of the following command sequence in UNIX?

grep "error" log.txt | sort | uniq -c | tee error_summary.txt | head -5

• Finds the first 5 unique error messages in log.txt and saves the output to error_summary.txt

• Counts and lists the first 5 unique lines containing "error" from log.txt and saves the output to error_summary.txt

• Displays the first 5 unique error messages from log.txt and does not save the output

• Finds, counts, sorts unique error messages from log.txt, saves the output to error_summary.txt, and displays the first 5 lines

You have a directory named project with multiple files. How would you recursively change the permissions so that the owner can read, write, and execute, and everyone else can only read and execute?

• chmod -R 755 project

• chmod -R 744 project

• chmod -R 751 project

• chmod -R 711 project

Given the following tables:

• Employees(emp_id, emp_name, dept_id)

• Departments(dept_id, dept_name)

• Salaries(emp_id, salary)

• Which SQL query retrieves the department name and the total salary for each department?

• SELECT d.dept_name, SUM(s.salary) FROM Departments d INNER JOIN Employees e ON d.dept_id = e.dept_id INNER JOIN Salaries s ON e.emp_id = s.emp_id GROUP BY d.dept_name

• SELECT dept_name, SUM(salary) FROM Employees e INNER JOIN Departments d ON e.dept_id = d.dept_id INNER JOIN Salaries s ON e.emp_id = s.emp_id

• SELECT d.dept_name, s.salary FROM Departments d JOIN Employees e ON d.dept_id = e.dept_id JOIN Salaries s ON e.emp_id = s.emp_id

• SELECT d.dept_name, SUM(s.salary) FROM Departments d, Employees e, Salaries s WHERE d.dept_id = e.dept_id AND e.emp_id = s.emp_id GROUP BY d.dept_name

Which XPath expression selects the titles of all books?

• //book/title

• //library/book[@title]

• //book[@title]

• //library//title

In a database, a relation R(A, B, C, D) is in 3NF if it meets which of the following criteria?

(choose up to 2 answers)

• For every non-trivial functional dependency A -> B, A is a superkey

• • There are no transitive dependencies in the relation

• Every attribute is functionally dependent on the primary key

Which of the following statements about CAP theorem in NoSQL databases is true?

• It is possible to achieve all three: Consistency, Availability, and Partition Tolerance simultaneously

• In the presence of a network partition, one has to choose between consistency and availability

• CAP theorem applies only to SQL databases

• CAP theorem ensures that a distributed database is always consistent

What does the following grep command do?

grep -E '^(ab|cd)' file.txt

• Matches lines in file.txt that start with 'ab' or 'cd'

• • Matches lines in file.txt that contain 'ab' or 'cd'

• Matches lines in file.txt that end with 'ab' or 'cd'

• Matches lines in file.txt that have 'ab' followed by 'cd'

Which XPath expression retrieves the names of all products priced above $30?

• //product[price > 30]/name

• //product[price>30.00]/name

• //product[price>30]/name

• //product[price > 30.00]/name

Which command sequence will find all .txt files in the current directory and its subdirectories, sort them by modification date, and display the 5 most recently modified ones?

• find . -name "*.txt" | xargs ls -lt | head -5

• find . -type f -name "*.txt" -exec ls -lt {} + | head -5

• find . -type f -name "*.txt" | xargs ls -lt | head -n 5

• find . -name "*.txt" -exec ls -lt {} \; | head -5