Top 10 Linux Shell Interview Questions and Practical Answers

1. How to abort a shell script?

Use exit with a non‑zero status, e.g., exit -1. When a script encounters a non‑zero exit code it terminates.

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

Running the script shows that execution stops before the second echo.

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

Use sed to delete the first line: sed '1d' file.txt. With the -i option you can edit the file in place: sed -i '1d' file.txt.

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

Combine sed to print the desired line and pipe to wc -c to count bytes, e.g.:

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

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

In vi (or vim) enable the list option: press Esc, type :set list and press Enter. This shows characters such as ^M.

5. How to create a shared directory where only the file creator can delete files?

Use the sticky bit:

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

The +t (sticky) bit allows only the file’s owner, the directory’s owner, or root to delete files.

6. What are the four main states of a Linux process?

Waiting – the process is waiting for resources.

Running – the process is currently executing.

Stopped – the process has been stopped by a signal or after completion.

Zombie – the process has terminated but still has an entry in the process table.

7. How to use the cut command?

cut

extracts selected columns or fields. Examples:

# cut -c1-10 txt_linuxmi          # first 10 characters of each line
# cut -d';' -f2,5,7 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 produces a line‑by‑line description of changes needed to make the files identical.

9. Can echo replace ls ?

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

10. What is an inode?

An inode is a data structure that stores metadata about a file in Unix‑like systems; each file has a unique inode number.