Shell Scripting Interview Questions and Answers – A Beginner’s Guide

If you're preparing for a Linux admin, DevOps, or automation role, shell scripting is often a key skill tested in interviews. This blog covers common shell scripting interview questions with simple, clear answers to help you prepare confidently.

1. Basic Shell Scripting Questions

Q1. What is a shell script?

Answer:
A shell script is a text file containing a series of Linux commands that are executed sequentially. It helps automate repetitive tasks.

Example:

#!/bin/bash
echo "Hello, World!"

Q2. What is the shebang (#!) line?

Answer:
The shebang (#!) tells the system which interpreter (like /bin/bash) should execute the script.

Example:

#!/bin/bash  # Uses Bash shell
#!/bin/sh   # Uses the default shell

Q3. How do you make a script executable?

Answer:
Use chmod +x to give execute permission:

chmod +x script.sh
./script.sh  # Run the script

Q4. How do you add comments in a shell script?

Answer:
Use # for single-line comments:

# This is a comment
echo "Hello"  # Inline comment

2. Variables and Input/Output

Q5. How do you define and use a variable?

Answer:

name="Alice"  # Define
echo "Hello, $name"  # Use (with $)

Q6. How do you take user input in a script?

Answer:
Use read:

echo "Enter your name:"
read username
echo "Hello, $username!"

Q7. What is the difference between $@ and $*?

Answer:

• $@ → Treats each argument as a separate word.
• $* → Treats all arguments as a single string.

Example:

./script.sh arg1 arg2
# $@ = "arg1" "arg2"
# $* = "arg1 arg2"

3. Conditional Statements & Loops

Q8. How do you write an if-else statement?

Answer:

if [ condition ]; then
    # Code
else
    # Code
fi

Example:

if [ -f "file.txt" ]; then
    echo "File exists!"
else
    echo "File not found."
fi

Q9. How do you write a for loop?

Answer:

for i in 1 2 3; do
    echo "Number: $i"
done

Example (Loop through files):

for file in *.txt; do
    echo "Processing $file"
done

Q10. How do you write a while loop?

Answer:

count=1
while [ $count -le 5 ]; do
    echo "Count: $count"
    ((count++))
done

4. Functions & Command-Line Arguments

Q11. How do you define a function?

Answer:

function greet() {
    echo "Hello, $1!"
}
greet "Alice"  # Output: Hello, Alice!

Q12. How do you use command-line arguments?

Answer:

• $0 → Script name
• $1, $2 → First, second argument
• $# → Total arguments

Example:

echo "First argument: $1"
echo "Total arguments: $#"

5. File & Text Processing

Q13. How do you check if a file exists?

Answer:
Use -f:

if [ -f "file.txt" ]; then
    echo "File exists!"
fi

Q14. How do you search for text in a file?

Answer:
Use grep:

grep "error" logfile.txt

Q15. How do you replace text in a file?

Answer:
Use sed:

sed -i 's/old/new/g' file.txt

6. Error Handling & Debugging

Q16. How do you exit a script if a command fails?

Answer:
Use set -e:

#!/bin/bash
set -e  # Exit on error
rm non_existent_file  # Script stops if this fails

Q17. How do you debug a shell script?

Answer:
Run with -x for debugging:

bash -x script.sh

7. Real-World Scenarios

Q18. Write a script to find and delete old log files.

Answer:

#!/bin/bash
find /var/log -name "*.log" -mtime +30 -delete

Q19. Write a script to check disk space and alert if low.

Answer:

#!/bin/bash
threshold=90
usage=$(df / | awk 'NR==2 {print $5}' | tr -d '%')

if [ $usage -gt $threshold ]; then
    echo "Warning: Disk space low!"
fi

8. Best Practices

Q20. What are some shell scripting best practices?

Answer:
✔ Use comments (#) to explain code.
✔ Quote variables ("$var") to avoid errors.
✔ Use [[ ]] instead of [ ] for safer comparisons.
✔ Test scripts in small steps.

Final Tips for Interviews

• Practice writing scripts (file operations, loops, conditionals).
• Understand exit codes (0 = success, non-zero = failure).
• Be ready for real-world problems (log parsing, automation).

Conclusion

Shell scripting is a must-know skill for Linux and DevOps roles. These interview questions and answers cover basics to real-world scenarios.

🚀 Keep practicing, and you’ll ace your interview!

Got more questions? Ask in the comments! 💬🐧