Top 24 Shell Script Interview Questions and Answers Every Linux Engineer Should Know

Although Python is widely used in operations, many companies still ask shell script questions when hiring Linux cloud engineers. Below are common shell script interview questions and answers.

Q1: What is a shell script and is it necessary?

A shell script is a text file containing one or more commands. System administrators often combine multiple commands into a single script to automate routine tasks.

Q2: What is the default login shell and how to change a user's login shell?

The default login shell is /bin/bash. Use chsh to change it, e.g.:

# chsh <username> -s <new_shell>
# chsh linuxtechi -s /bin/sh

Q3: What types of variables can be used in shell scripts?

System-defined variables (usually uppercase, viewable with set)

User-defined variables (accessed with $VAR_NAME)

Q4: How to redirect both standard output and error to the same location?

Method 1: 2>&1 # ls /usr/share/doc > out.txt 2>&1 Method 2: &> # ls /usr/share/doc &> out.txt Q5: How to nest "if" statements in a shell script?

if [ condition ]
then
    # commands
else
    if [ condition ]
    then
        # commands
    else
        # commands
    fi
fi

Q6: What is the purpose of the $? variable? $? holds the exit status of the previous command; 0 means success.

# ls /usr/bin/shar
# echo $?
0

Q7: How to compare two numbers in a shell script?

#!/bin/bash
x=10
y=20
if [ $x -gt $y ]
then
    echo "x is greater than y"
else
    echo "y is greater than x"
fi

Q8: What does the break command do?

It exits the current loop (e.g., while or until).

Q9: What does the continue command do?

It skips the remainder of the current loop iteration and proceeds with the next iteration.

Q10: What is the syntax of a case statement?

case variable in
    value1)
        # commands
        ;;
    value2)
        # commands
        ;;
esac

Q11: What is the syntax of a while loop?

while [ condition ]
do
    # commands
 done

Q12: How to make a script executable? # chmod a+x myscript.sh Q13: What is the purpose of #!/bin/bash ?

It is the shebang line that tells the system to execute the script using /bin/bash.

Q14: What is the syntax of a for loop?

for variable in list
do
    # commands
 done

Q15: How to debug a shell script?

Use the -x option ( sh -x myscript.sh) or -nv ( sh -nv myscript.sh).

Q16: How to compare strings in a shell script?

Use the test command or [ ] with string operators.

Q17: What special variables does Bourne shell (bash) provide?

$0   script name
$1   first argument
$2   second argument
...  
$#   number of arguments
$*   all arguments as a single word

Q18: How to test files in a shell script?

-d file   # true if directory
-e file   # true if exists
-f file   # true if regular file
-r file   # true if readable
-s file   # true if non‑empty
-w file   # true if writable
-x file   # true if executable

Q19: How to write comments in a shell script? # This is a comment Q20: How to read input from the terminal?

#!/bin/bash
echo "Please enter your name"
read name
echo "My Name is $name"

Q21: How to unset a variable? # unset <variable_name> Q22: How to perform arithmetic operations?

Method 1: expr 5 + 2 Method 2: result=$[16 + 4] Q23: What is the basic format of a do‑while loop?

do {
    # commands
} while (condition)

Q24: How to define a function in a shell script?

myfunc () {
    # commands
}