Prepare for your next Shell Scripting interview with this comprehensive guide featuring 30 essential questions. Covering basic concepts to advanced scenarios, these questions help freshers, candidates with 1-3 years experience, and professionals with 3-6 years prepare effectively. All examples use pure Shell Scripting techniques.
Basic Shell Scripting Interview Questions (1-10)
1. What is a shell script?
A shell script is a text file containing a sequence of shell commands executed by the shell interpreter to automate repetitive tasks.[1][3]
2. What is the purpose of the shebang (#!) line in a shell script?
The shebang line specifies the shell interpreter to execute the script, such as #!/bin/bash for Bash or #!/bin/sh for POSIX shell.[4]
3. How do you run a shell script in the background?
Add & at the end of the command: ./script.sh &[1]
4. What does the $? variable represent?
$? returns the exit status of the last executed command (0 for success, non-zero for failure).[1]
5. How do you add comments in a shell script?
Use the # symbol. Everything after # on a line is ignored by the shell.
#!/bin/bash
# This is a comment
echo "Hello World"[3]
6. What is the difference between $ and $$?
$ references a variable value, while $$ represents the Process ID (PID) of the current shell.[3]
7. How do you make a shell script executable?
Use chmod +x script.sh to add execute permission.[2]
8. What are positional parameters in shell scripting?
Positional parameters ($1, $2, etc.) represent command-line arguments passed to the script.[4]
9. What does $0 represent?
$0 contains the name of the script itself.[4]
10. How do you print the current working directory in a script?
Use the pwd command: echo $(pwd)[2]
Intermediate Shell Scripting Interview Questions (11-20)
11. What are the different types of shell variables?
Local variables (script-specific), environment variables (exported with export), and special variables like $@, $#.[5]
12. How do you check if a file exists in a shell script?
Use [ -f filename ] for regular files or [ -e filename ] for any file type.
if [ -f /etc/passwd ]; then
echo "File exists"
fi[2]
13. Explain the use of > and >> operators.
> redirects output and overwrites the file, while >> appends to the file.[1]
14. How do you read user input in a shell script?
Use the read command: read username[3]
15. Write a script to check if a number is positive, negative, or zero.
#!/bin/bash
echo "Enter a number:"
read num
if [ $num -gt 0 ]; then
echo "Positive"
elif [ $num -lt 0 ]; then
echo "Negative"
else
echo "Zero"
fi[3]
16. What is the difference between [ ] and [[ ]]?
[ ] is POSIX test command; [[ ]] is Bash keyword with better string handling and no word splitting.[2]
17. How do you loop through all files in a directory?
Use for loop:
for file in *; do
echo "$file"
done[1]
18. What does $# represent?
$# gives the number of positional parameters (arguments) passed to the script.[4]
19. How do you substitute the value of a variable in a string?
Use double quotes: name="John"; echo "Hello $name"[3]
20. At Zoho, how would you create a script to backup log files daily?
#!/bin/bash
tar -czf /backup/logs_$(date +%Y%m%d).tar.gz /var/log/*.log[1]
Advanced Shell Scripting Interview Questions (21-30)
21. Explain the three file permissions in shell scripting.
Read (r), Write (w), and Execute (x) permissions control access for owner, group, and others.[2]
22. How do you handle signals in shell scripts?
Use trap command: trap 'echo "Script interrupted"' INT[5]
23. Write a script to find and print numbers divisible by both 3 and 5 up to 100.
#!/bin/bash
for i in {1..100}; do
if [ $((i%3)) -eq 0 ] && [ $((i%5)) -eq 0 ]; then
echo $i
fi
done[6]
24. What is the purpose of set -e?
set -e exits the script immediately if any command returns a non-zero status.[5]
25. How do you parse command-line arguments in a script?
Use while case with shift:
while [ $# -gt 0 ]; do
case $1 in
-f) shift; file=$1 ;;
esac
shift
done[4]
26. For Atlassian tools monitoring, write a script to check disk usage and alert if over 80%.
#!/bin/bash
usage=$(df / | grep / | awk '{print $5}' | sed 's/%//g')
if [ $usage -gt 80 ]; then
echo "Disk usage critical: $usage%"
fi[3]
27. Explain awk field separators with an example.
$1, $2 represent first and second fields: awk '{print $1}' file.txt prints first column.[1]
28. How do you create a function in shell scripting?
myfunc() {
echo "Function called"
}
myfunc[5]
29. At Salesforce, how would you write a script to rotate logs older than 7 days?
#!/bin/bash
find /var/log -name "*.log" -mtime +7 -exec rm {} \;[1]
30. What is array handling in Bash, and provide an example?
Bash supports arrays:
fruits=("apple" "banana" "orange")
echo ${fruits[1]} # banana
echo ${fruits[@]} # all elements[4]
