Oracle Unix Interview Questions and Answers

1. What is UNIX?
Answer: It is a portable operating system that is designed for both efficient multi-tasking and multi-user functions. Its portability allows it to run on different hardware platforms. It was written in C and lets the user do processing and control under a shell. (oracle unix interview questions)

2. What is a Wild-Card Interpretation?
Answer: A command-line includes wild-card characters such as ‘*’ or ‘?’. They are substituted by the shell with an organized list of files whose pattern matches the input command. Wild-card fonts set up a list of files for processing instead of having it stipulated one at a time.

3. What are the main features of UNIX?

  • Machine independent
  • Portability
  • Multi-user operations
  • Unix Shells
  • Hierarchical file system
  • Pipes and filters
  • Background processors
  • Utilities
  • Development tools.

4. Describe links and symbolic links in UNIX?
Answer: The second name for a file called a Link. It is used to assign more than one name for a file. It is not valid to assign more than one name to a directory or to link filenames on different computers.

General command ‘– ln filename1 filename2’

A symbolic link is the files that use to contain only the name of other files included in it. Directed to the files pointed by it is the operation of the symbolic link.

General command ‘– ln -s filename1 filename2’.

5. What is the best way of viewing this course?
Answer: You have to just watch the course from beginning to end. Once you go through all the videos, try to answer the questions in your own words. Also, mark the questions that you could not answer by yourself. Then, in the second pass go through only the difficult questions. After going through this course 2-3 times, you will be well prepared to face a technical interview in the Unix topic.

6. What is a Kernel?
Answer: The kernel is the UNIX operating system master program that controls the computer’s resources assigning them to different users and carrying out different tasks. However, the Kernel doesn’t have direct dealings with a user. It begins a separate interactive program called a shell for each user when they log on.

7. How do you find which processes are using a particular file?
Answer: By using the soft command in UNIX. It will list down PID of all the process which is using a particular file.

8. How are devices represented in UNIX?
Answer: All devices are represented by files called special files that are located in/dev directory. Thus, device files and other files are named and accessed in the same way. A ‘regular file’ is just an ordinary data file in the disk.

9. How will you run a process in the background? How will you bring that into the foreground and how will you kill that process?
Answer: For running a process in background use “&” in the command line. For bringing it back in foreground use command “FG jobid” and for getting job id you use command jobs, for killing that process find PID and use kill -9 PID command. This is indeed a good Unix Command interview question because many programmers not familiar with the background process in UNIX.

10. You have an IP address in your network how will you find hostname and vice versa?
Answer: This is a standard UNIX command interview question asked by everybody and I guess everybody knows its answer as well. By using the nslookup command in UNIX, you can read more about converting IP Address to the hostname in Unix here. (e learning)
I hope these UNIX command interview questions and answers would be useful for a quick glance before going for any UNIX or Java job interview. Please share any interesting UNIX command interview you have come across and I will add into this list. If you are going for any Unix interview on brokerage firm or stock trading company or any Investment bank you can have a quick look here, though most of the questions you might already know its good to review it.

11. What is the description for Kernel?
Answer: Kernel is the master program with a UNIX operating system that controls the resources of the computer. The resource allocation to different users and tasks handled by this section. The kernel does not have direct communication with the user and it starts separate interactive program call shell to each user when login to the system.

12. What is mean by Super User?
Answer: The user with access to all files and commands within the system is called a superuser. Generally, the superuser login is to root and the login is secured with the root password.

13. What is the process group?
Answer: A collection of one or more processes is called a process group. There is a unique process id for each process group. The function “getpgrp” returns the process group ID for the calling process.

14. Describe the fork() system call?
Answer: The command used to create a new process from an existing process is called fork().The main process is called the parent process and the new process id called child process. The parent gets the child process id returned and the child gets 0. The returned values are used to check which process which code executed.

The returned values are used to check which process which code executed.

15. What are the Filters?
Answer: A Filter refers to a program that can get input from typical input, perform an operation on the output and write results to standard output. A Filter is also any program that can be used between two other programs in a pipeline.

16. What is not up in UNIX?
Answer: Nohup is a special command which is used to run the process in the background, but it is slightly different than & which is normally used for putting a process in the background. A UNIX process started with nohup will not stop even if the user who has stared log off from the system. While the background process started with & it will stop as soon as the user logs off.

17. How do you check if a particular process is listening on a particular port on the remote host?

Answer: By using telnet command for example “telnet hostname port”, if it can successfully connect then some process is listening on that port. To read more about telnet read networking command in UNIX.

18. What is the difference between HardLink and SoftLink in UNIX?
Answer: I have discussed this Unix Command Interview questions in my blog post difference between Soft link and Hard link in Unix.

19. How do you find which process is taking how much CPU?
Answer: By using the “top” command in UNIX, there could be multiple follow-up UNIX command interview questions based upon the response of this because the “TOP” command has various interactive options to sort results based upon a various parameter.

20. What is the Zombie process in UNIX? How do you find a Zombie process in UNIX?
Answer: When a program forks and the child finishes before the parent, the kernel still keeps some of its information about the child in case the parent might need it – for example, the parent may need to check the child’s exit status. To be able to get this information, the parent calls ‘wait()’; In the interval between the child terminating and the parent calling ‘wait()’, the child is said to be a ‘zombie’ (If you do ‘ps’, the child will have a ‘Z’ in its status field to indicate this.)
Zombie: The process is dead but has not been removed from the process table.

21. What is an ephemeral port in UNIX?
Answer: Ephemeral ports are port used by the Operating system for client sockets. There is a specific range on which OS can open any port specified by the ephemeral port range.

22. What are Key Features of the Korn Shell?
Answer: The features are:

• Job control
• Arrays.
• Command Aliasing.
• String manipulation capabilities.
• Built-in Integer Arithmetic.
• History mechanism with a built-in editor that copies emacs or VI.

23. What are the topics covered in this course?
Answer: We cover a wide range of topics in this course. We have questions on Unix commands, concepts, etc.

24. What is a single-user system?
Answer: A personal computer with an operating system that was designed to operate by a single user at a given time. Single user systems become more popular since low-cost hardware and availability of a wide range of software to perform different tasks.

25. Explain the following sentence?
Answer: It is not advisable to use root as the default login.

The root account is very important and it can leads to system damage easily with abusive usage. So that the securities that normally apply to user accounts do not apply to the root account.

26. What is FIFO?
Answer: FIFO (First In First Out) is also called named pipes and it is a special file for date transient. Data is read-only in the written order. This is used to inter-process communications, where data write to one end and reads from another end of the pipe.

27. What is the utilization of interfaces?
Answer: An interface takes after a class in which none of the strategies have been executed—the system marks are there, yet the body of each methodology is void. To use an interface, another class must realize it by giving a body to most of the procedures contained in the interface. Interfaces can give a layer of reflection to your code. They isolate the specific execution of a system from the declaration for that procedure. In this manner, you can have unmistakable use of a methodology in perspective of your particular application.

28. What are the responsibilities of a shell?

  • Program Execution
  • Input/output redirection
  • Filename and variable substitution
  • Pipeline hookup
  • Environment control
  • Integrated programming language.

29. What is the UNIX command to list files/folders in alphabetical order?
Answer: The ‘ls –l’ command is used to list down files and folders in alphabetical order. When you use ‘ls –lt’ is list down files /folders sorted with modified time.

30. What are the different file types available with UNIX?

  • Regular files
  • Directory files
  • Character special files
  • Block special files
  • FIFO
  • Symbolic links
  • Socket

31. Describe the term directory in UNIX?
Answer: A specialized form of a file that maintains a list of all the files which include in it is called a directory. Each file assigns to a directory.

32. What is called Shell?
Answer: The interface between user and system called a shell. Shell accepts commands and set them to execute for user operations. 

33. What is the level of questions in this course?
Answer: This course contains questions that are good for a Fresher to an Architect level. The difficulty level of question varies in the course from a Fresher to an Experienced professional.

34. How do I separate development from the production environment?
Answer: Depending on requirements for the availability of the application, the size of the user population and other factors you can decide how to divide the development environment from the production environment.
For certain applications, it is acceptable to combine the development server with the deployment server, as long as the end users understand that sometimes the application is not available.
Other applications may require two (development and production) or even three (development, test, and production) servers.
In Application Express applications can be moved from environment to environment using an export and import facility for application definitions.
With one server available to run the database and Application Express, you can still separate the development version of an application from its production version by using two workspaces accessing separate schemas.
In this case, one workspace will be used by developers and the other will be the workspace in which the application is deployed in production.

35. What is Inode?
Answer: An inode is an entry on a section of the disk set which is set aside for a file system. The inode holds nearly all the information about a file. It includes:

• The place on the disk where the file starts.
• Who owns the file.
• The size of the file.
• When the file was last used.
• When the file was last changed.
• What the various read, write and execute permissions are.

An Online Course in UNIX Fundamentals.

Online IT Courses offers a course in UNIX fundamentals. You will get technical knowledge on how to organize, install and manage UNIX. You will learn to:

• Organize UNIX
• Configure and manage devices.
• Make use of the command line.
• Add groups and users.
• Set up a firewall.

  • A Prerequisite – having technical knowledge of operating systems is a bonus.
  • Target Audience – System Administrator.
  • Bonuses –Limitless access to their IT professionals’ community.

Available consultants to advise you about the study and career options.
Certified teachers with profound knowledge.
Access to the platform.
When you feel confident enough to start a career in the field put together your resume and prepare for the interview by studying the UNIX interview questions. You are also able to get qualifications. UNIX is quite logical, so knowledge of basic commands and a little imagination will get you through the interview. Hopefully, this will lead to a rewarding career.

36. Is it Possible to See Information About a Process While it is Being Executed?
Answer: Every process is uniquely recognized by a process identifier. It is possible to view details and status concerning a process by using the ‘ps’ command. 

37. What is the different type of variables used in a Shell Script?
In a shell script we can use two types of variables:

System-defined variables
User-defined variables
System-defined variables are defined or created by Operating System(Linux) itself. These variables are generally defined in Capital Letters and can be viewed by “set” command.

38. What is the session?
Answer: A Session is a collection of one or more process groups. A process establishes a new session by calling setsid function. This function return process groupid ok.

39. If one process is inserting data into your MySQL database? How will you check how many rows inserted into every second?
Answer: The purpose of this Unix Command Interview is asking about watch command in UNIX which repeatedly executes command provided with specified delay.

40. What is ‘ps’ command for?
Answer: The ps command prints the process status for some or all of the running processes. The information given is the process identification number (PID), the amount of time that the process has taken to execute so far, etc.

41. What is RAW datatype?
Answer: The RAW data type is used in storing values in binary data format. The maximum size of a RAW in a table is 32767 bytes. 

42. Do you have a tab-separated file that contains Name, Address and Phone Number, list down all Phone Number without there name and Addresses?
Answer: To answer this Unix Command Interview question you can either you AWK or CUT command here. CUT use tab as default separator so you can use
cut -f3 filename.

43. What is the “chmod” command?
Answer: chmod command is used to change the permission of a file or directory in UNIX. The line you see shows the permission for three different sets of people: user, group and others. User is the currently logged in user, while the group is for all other members which are part of a certain group and others mean anyone other than user and group member. Each group has three permissions rwx stands for reading, write and execute and they are written as user_group_others. So in the above line, the user has only read permission, group members have to write permissions and other people have only executed permission. If it is a directory then you need to execute permission to go inside that directory.

44. How do you check how much space left in the current drive?
Answer: By using the “df” command in UNIX. For example “df -h .” will list how full your current drive is. This is part of anyone day to day activity so I think this Unix Interview question will be to check anyone who claims to work in UNIX but not working on it.

45. What is the kernel in UNIX?
Answer: The kernel is the name of the Operating System in UNIX. It is the kernel Job to keep each process and user separate and to regulate to access the system hardware

46. Write a command to list all the links from a directory?
Answer: In this UNIX command interview questions interviewer is generally checking whether the user knows the basic use of “ls” “grep” and regular expression etc. You can write the command like ls -lrt | grep “^l”

47. What is the fastest query method to fetch data from the table?
You can use ROWID to fetch Row from the table. The use of ROW ID is the fastest query method for fetching data from the table.

48. How do you see command line history in UNIX?
Answer: Very useful indeed, use history command along with a grepping command in UNIX to find any relevant command you have already executed. Purpose of this Unix Command Interview Questions is probably to check how familiar candidate is from available tools in the UNIX operating system.

49. What is the difference between ps -ef and ps -auxwww?
UNIX interview questions answers, UNIX Linux questions this is indeed a good Unix Interview Command Question and I have faced this issue while ago where one culprit process was not visible by executing ps –ef command and we are wondering which process is holding the file.
ps -ef will omit process with very long command line while ps -auxwww will list those processes as well.

50. How will this course help me?
Answer: By attending this course, you do not have to spend time searching the Internet for Unix interview questions. We have already compiled the list of the most popular and the latest Unix Interview questions.

51. What type of buffer is supported by Unix?

Fully Buffered.
Line Buffered.

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