TOP 15 Unix Interview Questions and Answers [UPDATED 2024]

Unix Interview Questions and Answers

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Unix interview questions are considered to be some of the most challenging questions in the IT industry.

Unix began as a research project at AT&T Bell Labs in the mid-1960s. It later evolved into a full-fledged operating system intended for both efficient multitasking and multi-user features. It is hardware agnostic. It is built in such a way that users may do processing and gain control through the usage of a shell. The UNIX operating system is extremely customizable and has grown into a highly sophisticated, adaptable, and scalable operating system capable of handling nearly any modern-day user job.

Before we get into the meat of the top Unix interview questions and answers, it is crucial to note that each Unix interview question in this article has been chosen by experienced hiring managers with years of experience in the industry.

15 Unix Interview Questions and Answers in 2024

Another point to take into consideration is the top Unix interview questions included in this article are sufficient, but it wouldn’t hurt to do extra study and get more information.

What are the core components of Unix?

Answer: Unix consists of three parts: the kernel, the shell, and the file programs. They are in detail further below:

  • Kernel: The kernel is the operating system’s lowest layer. The kernel, sometimes known as the core of Unix, interacts directly with the computer hardware. It is in charge of assigning and administering the resources made available to programs. It keeps track of important operations, including memory management, file management, and job scheduling. It also provides an interface for applications to access files, the network, and devices.
  • The shell: refers to a command prompt. It’s in charge of connecting the user to the operating system. The shell converts the user’s input into the language recognized by the command prompt.
  • Programs: Unix provides a wide range of tiny programs to satisfy a variety of purposes. Each Unix application only does one thing. Because of the modular design, tiny program functions may be merged and matched. This provides consumers with flexibility, allowing them to do nearly any work. While programs run on top of the shell, they can also communicate with the kernel directly.

List some features of UNIX.

Answer: UNIX includes the following features, pay an extra attention because this is one of the best and updated, and top Unix interview questions of all time:

Unix Interview Questions
Some of Unix features by

UNIX supports the multiuser system: In UNIX, it is possible for many users to use the system with their separate workspace and logins has full support for the multiuser environment.

UNIX supports the multitasking environment: In UNIX many apps can run at a single instance of time. This is also referring to a multitasking environment.

What is a single-user system?

Unix Interview Questions
A single-user system by

Answer: A single-user system is a personal computer with an operating system designed to be operated by a single user at a given time. These systems have become more popular since low-cost hardware and the availability of a wide range of software to perform different tasks.

What is FIFO?

Answer: FIFO (First In First Out) is a particular file for date transients. It refers to pipes. In the written order, data is only readable. This is useful for inter-process communication when data is on paper at one end of the pipe and read from the other.

Describe fork() system call?

Answer: Fork is the command used to generate a new process from an existing one (). The primary process is referred to as the “parent”, while the new process id is the “child”. The parent process receives the child process id, and the child receives 0. The returned values are useful to validate the process and the code that was running.

What is Super User?

Answer: For this Unix interview question, the answer would be something like this: A superuser is a user who has access to all files and commands in the system. In most cases, the superuser login is to root, and the login is safe with the root password.

Discuss the difference between swapping and paging?


Swapping: The whole process alters the main memory for execution. The process size must be less than the available main memory capacity in order to meet the memory requirement. The implementation is simple, but it adds a burden to the system. Memory management is not more adaptable with swapping systems.

Paging: Only the memory pages that are necessary for execution are transformed into the main memory. The size of the process is irrelevant for execution, and it does not need to be less than the available memory capacity. Let several processes load into the main memory at the same time.

What is the explanation for protection fault?

Answer: Before we get to the meat of this Unix interview answer, I would like to inform you that this is one of the best and updated, top Unix interview questions of all time. A protection fault occurs when the process attempts to visit a page that does not have access authorization. A protection error is also taking place when a process attempts to write on a page whose copy on the write bit was ready during the fork() system function.

What is piping?

Answer: The term “piping” refers to the process of combining two or more instructions. The first command’s output serves as the input for the second command, and so on. The piping symbol (|) is useful to represent the pipe character (|).

What do you understand by UNIX shell?

Unix Interview Questions
UNIX shell by

Answer: The UNIX shell provides an environment in which commands, programs, and shell scripts can take place, as well as an interface between the user and the Unix operating system. Shell’s command prompt is “$,” which reads input and selects which command to run.

What do understand by Kernel?

Answer: The Unix operating system is already divided into three sections: the kernel, the shell, and the commands and tools. Instead of acting as a separate interactive application for those who have signed in, the kernel is the heart of the Unix operating system, and it does not communicate directly with users.

What do you understand by shell variables?

Answer: A variable is the name given to a character string that is useful for storing a value; values might be numbers, text, filenames, and so on. The shell keeps track of the collection of internal variables and allows for variable deletion, assignment, and creation.

As a result, shell variables are a mix of identifiers and values that live within the shell. Local variables are declared in a shell function in a specific fashion. They may have a default value or values can be changed by using the relevant assignment command.

  • This command is useful for defining a shell variable.
  • The ‘unset’ command is useful for removing shell variables

Describe the responsibilities of Shell in brief.

Answer: This is one of the most updated Unix interview questions of all time. The Shell performs a variety of functions, including evaluating the input line and beginning the execution of the program submitted by the user.

The following is a summary of the responsibilities:

  • The shell is in charge of executing all programs by evaluating the line and deciding the actions needed before launching the specified application.
  • When you use variables on the command line, the shell allows you to set values for them. Filename replacement is also in place of support.
  • To deal with input and output redirection.
  • Pipeline hook-up is doing well by connecting the standard output of the command preceding the ‘|’ to the standard input of the command following the ‘|’.
  • It includes commands for customizing and controlling the environment.
  • It has its own built-in integrated programming language, which makes it easy to debug and change.

How is the CMP command different from the diff command?

Answer: The “CMP” command is useful for comparing two files byte by byte to find the first mismatched byte. This command does not utilize the directory name and instead reports the first mismatched byte detected.

The “diff” command, on the other hand, identifies the modifications that must be made to the files in order to make the two files similar. Directory names can be useful in this scenario.

Explain what is Pid?

Answer: A PID is a unique process identifier. It essentially identifies all of the processes running on the Unix system. It makes no difference if the processes are operating in the front end or the back end.

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