Unix Interview Question

A list of top frequently asked Unix interview questions and answers are given below.

1) What is Unix?

UNIX is a portable operating system that is designed for efficient multi-tasking and multi-user functions. Since it is a portable operating system, it can run on different hardware platforms.

It is written in C language.

2) What is a UNIX shell?

The UNIX shell is a program which is used as an interface between the user and the UNIX operating system. It is not a part of the kernel but it can communicate directly with the server.

3) What is filter?

A filter is a program that takes input from standard inputs and performs some operation on that input to produce a result as standard output.

4) What are the devices represented in UNIX?

All devices in UNIX are represented by special files that are located in /dev directory.

5) Is there any method to erase all files in the current directory, along with its all sub-directories, by using only one command?

Yes, you should use "rm-r*" command for this purpose.

Here the "rm" command is used for deleting files, the ?r option will erase directories and sub directories with their internal files and * is used for selecting all entries.

6) What is necessary before you can run a shell script from the command line prompt?

You must make the shell script executable by using the UNIX "chmod" command.

7) How to terminate a shell script if statement?

A shell script if statement can be terminated by using "fi".

8) Write down some common shells with their indicators?

• sh - Bourne shell
• csh - C SHell
• bash - Bourne Again Shell
• tcsh - enhanced C Shell
• zsh - Z SHell
• ksh - Korn SHell

9) What are the main features of Korn Shell?

• Arrays
• Job control
• Command Aliasing
• String manipulation ability
• Built-in integer arithmetic

10) What is the difference between cat and more command?

The cat command is used to display the file contents. If the file is large and you have to scroll off the screen before you view it so command more is like a pager which displays the screen page by page.

11) Which command is used to restrict incoming messages?

The "mesg" command is used to restrict incoming messages.

12) Which command is used to kill the last background job?

The "kill $!" Command is used to kill the last background job.

13) Which data structure is used to maintain the file identification?

The "inode" data structure is used to maintain the file identification. Each file has a separate inode and a unique inode number.

14) What is pipe?

A pipe is a two or more commands separated by pipe "I" character. It is used to tell the shell to arrange for output of the preceding command.

15) What are the links and symbolic links in a UNIX file system?

A link is a second name for a file. Links are used to assign more than one name to a file, but cannot be used to assign a directory more than one name or link file names on different computers.

Symbolic links are the files that only contain the name of another file. The operations on the symbolic link are directed to the file pointed by it. Both the limitations of links are eliminated in symbolic links.