BSIT3201-Finals

1. Which of the following best explains why using #!/bin/bash at the beginning of a script is important?

• It makes the script executable.

• It defines the location of the shell to execute the script.

• It comments out the second and last line of the executable script

• It sets the default permissions of the file in bash scriptng

2. You are writing a script to check disk space. Which command combination is most effective for storing and analyzing the used disk percentage?

• ls | grep

• df -h | awk '{print $5}'

• du -h | head -1

• ps aux | sort

3. Which statement is true regarding variables in shell scripting?

• All variables must be declared with var int.

• Variables are declared with a dollar sign $ prefix.

• Variable values are assigned using = without spaces.

• All variables are automatically global.

Answer explanation

Shell variable syntax requires no space before or after the =.

4. What will the following script output?
   bash

5. x=5
   y=10

   echo $((x+y))

• x+y

• 15

• 5+10

• Error

Answer explanation

The $(( )) evaluates arithmetic expressions.

5. Why is chmod +x script.sh necessary before executing a script directly?

• It changes the owner of the script.

• It adds write permissions to the script.

• It allows the script to be executed.

• It creates a backup of the script.

Answer explanation

The +x flag gives execute permission.

A system admin wants to create a backup script that copies all .conf files from /etc to /backup and logs the time of backup.
Which of the following commands is most appropriate in the script?

• cp /etc/*.conf /backup && date >> log.txt

• mv /etc/*.conf /backup && time >> log.txt

• cat /etc/*.conf > /backup && echo $date >> log.txt

• ls /etc/*.conf | cp /backup && echo date >> log.txt

Answer explanation

This line copies .conf files and logs the date after a successful operation.

7. You wrote a script with this snippet:

What would happen if the user entered a non-numeric input like "abc"?

• The script prints "Low".

• It compares text and prints "High".

• It shows a syntax error.

• It crashes with an error message.

Answer explanation

Non-numeric input will cause [ $num -gt 10 ] to fail, leading to an error

8. A user complains that their script doesn’t respond to keyboard interrupts (Ctrl+C) during a loop. What is the best way to handle this in the script?

• Add trap 'exit' INT at the beginning.

• Use kill -9 $$ inside the loop.

• Add continue to the loop.

• Use echo off to ignore input.

Answer explanation

trap is used to catch and handle signals like SIGINT (Ctrl+C).

9. You want to display all files modified in the last 24 hours using a script. Which command best fits?

• ls -lt

• find . -mtime -1

• grep "today" *

• history | tail

Answer explanation

find with -mtime -1 finds files modified within the last 24 hours.

Your script processes user data from a file line by line. Which loop is best suited for this task?

• for user in file; do ...

• while read user; do ... done < file

• until read user; do ... done < file

• if read user; then ... fi

Answer explanation

The while read loop is reliable for reading file lines in bash.