Essential Linux Shell Interview Questions and Practical Answers

Linux offers a vast landscape for developers, and mastering common shell tasks is valuable for both career growth and knowledge expansion. Below are practical interview‑style questions with clear answers and command examples.

1. How to abort a shell script before it finishes?

Use the exit command. Exiting with a non‑zero status (e.g., exit -1) causes the script to terminate with an error. Example script:

#!/bin/bash
 echo "Hello"
 exit -1
 echo "bye"

Running it yields:

# sh linuxmi.sh
 Hello
 linuxmi.sh: line 3: exit-1: command not found
 bye

2. How to remove the header line of a file?

The sed command can delete specific lines. To delete the first line: sed '1 d' file.txt With the -i option you can edit the file in place:

sed -i '1 d' file.txt

3. How to check the length of a specific line in a text file?

Combine sed to select the line and pipe to wc -c to count characters. Example for the fifth line:

sed -n '5 p' linuxmi.txt | wc -c

4. How to display all non‑printable characters in a file?

Open the file in vi, enter command mode with :, and run: set list This shows characters such as ^M.

5. How to create a shared directory where members can create files but only owners can delete them?

Use the sticky bit:

# mkdir dir_xyz
# chmod g+wx dir_xyz
# chmod +t dir_xyz

The +t (sticky) bit ensures only the file owner, directory owner, or root can delete files.

6. What are the main lifecycle stages of a Linux process?

Waiting – the process is waiting for resources.

Running – the process is actively executing.

Stopped – the process has finished or received a termination signal.

Zombie – the process has terminated but remains in the process table.

7. How to use the cut command?

cut

extracts sections of each line of a file. Examples:

# cut -c1-10 txt_linuxmi        # first 10 characters
# cut -d';' -f2 -f5 -f7 txt_linuxmi  # fields 2, 5, and 7 using ';' as delimiter

8. Difference between cmp and diff ?

cmp

compares two files byte‑by‑byte and reports the first mismatch. diff shows the changes needed to make the files identical, providing a more readable diff output.

9. Can echo replace ls ?

Yes, echo * lists the same filenames as ls in the current directory, though formatting differs.

10. What is an inode?

An inode is a data structure on Linux/Unix file systems that stores metadata about a file, including its unique inode number.