Unix Interview Questions and Answers

This section covers frequently asked Unix interview questions.

1. What is Unix?

Unix is a portable, multitasking, multi-user operating system. It's known for its efficiency and flexibility.

2. Unix Distributions.

(This section would list various Unix distributions, such as Solaris, AIX, HP-UX, BSD, etc.)

3. Features of Unix.

• Multi-user capabilities
• Multitasking

4. Core Concepts of Unix.

• Kernel: The core of the operating system, managing hardware and processes.
• Shell: A command-line interpreter.
• Commands and Utilities: Built-in tools for various tasks.
• Directories: Organize files in a hierarchical structure.

5. What is a Unix Shell?

A shell is a command-line interpreter that allows users to interact with the Unix operating system.

6. What is a Filter?

A filter is a program that takes input, processes it, and outputs the result.

7. Device Representation in Unix.

Devices are represented as files in the /dev directory.

8. Deleting Files and Subdirectories.

Use the command rm -r * (use with caution!).

9. Making a Shell Script Executable.

Use the chmod command (e.g., chmod +x myscript.sh).

10. Terminating an if Statement.

Use fi.

11. Common Unix Shells.

(This section lists common Unix shells and their names, such as Bourne shell (sh), C shell (csh), Bash (bash), etc.)

12. Features of Korn Shell (ksh).

• Arrays
• Job control
• Command aliasing
• String manipulation
• Built-in arithmetic

13. cat vs. more Commands.

cat displays the entire file content. more displays page by page.

14. Restricting Incoming Messages.

Use the mesg command.

15. Killing the Last Background Job.

Use the command kill $!.

16. File Identification Data Structure.

Inode.

17. Pipes in Unix.

Pipes (|) connect the output of one command to the input of another.

18. Links and Symbolic Links.

A hard link is an additional name for an existing file. A symbolic link (symlink) is a pointer to a file.

19. Unix System Bootup.

(This section would detail the typical boot process in a Unix-like system, involving BIOS/UEFI, bootloader, kernel initialization, and the launching of the init process.)

20. Changing Your Password.

Use the passwd command.

21. Listing Directories.

(This section would list various options with the `ls` command for controlling output.)

22. Displaying the Date.

Use the date command.

23. Logging Out.

Use the logout command.

24. System Shutdown Commands.

(This section lists common commands for shutting down a Unix-like system: `halt`, `init 0`, `init 6`, `poweroff`, `reboot`, `shutdown`.)

25. Types of Unix Files.

• Regular files
• Directories
• Special files (devices)

26. Hidden Files.

Files whose names begin with a dot (.) are hidden files.

27. Single Dot (.) vs. Double Dot (..).

• .: Current directory
• ..: Parent directory

28. Creating Files.

Use a text editor (like vi) or the touch command.

29. Displaying File Contents.

Use the cat command (and options like -b for line numbers).

30. Counting Words in a File.

Use the wc command (e.g., wc -w filename).

31. Creating a Blank File.

Use the touch command.

32. Finding the Present Working Directory.

Use the pwd command.

33. Getting File Information.

Use the file command.

34. Changing the Directory.

Use the cd command.

35. Moving Files.

Use the mv command.

36. Copying Files.

Use the cp command (e.g., cp -r source destination for recursive copying).

37. Removing Files in Unix.

Use the rm command. The -r option removes directories and their contents recursively (use with caution!).

rm filename  #Removes a single file
rm -r directory_name #Removes a directory and its contents recursively

38. Creating a Directory.

Use the mkdir command.

mkdir directory_name

39. Removing a Directory.

Use the rmdir command (to remove an empty directory) or `rm -r` (to remove a directory and its contents).

rmdir directory_name  #Removes an empty directory
rm -r directory_name #Removes a directory and its contents recursively