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UNIX COMMANDS INTERVIEW QUESTIONS AND ANSWERS PDF

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UNIX command Questions Answers asked in Interview. UNIX or Linux operating system has become default Server operating system and for whichever. Unix Commands Interview Questions – Subscribe to FREE & Exclusive UNIX Commands Interview. Questions. Check for your FREE Bonuses at the end of this eBook . FREE Bonus #1 – + Technical Interview Questions with Answers. Here I have collected UNIX interview questions with their answers for your reference. If you require download UNIX Faqs in PDF format. An archive can be created in UNIX or Linux by using the tar command you can also create a.


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Unix and Linux Command Interview Questions and Answers .. Can you please shared pdf download link for these UNIX and Linux questions. what is unix, unix shell, steps UNIX shell follows while processing a command, cmp & diff in UNIX, grep command, cat & more UNIX prompts. Unix Interview Questions You Should Be Ready For. What command can you use to display the first 3 lines of text from a file and how In order to successfully pass this part of the interview, make sure you formulate your answers as clear.

What is ephemeral port in UNIX?

Ephemeral ports are port used by Operating system for client sockets. There is a specific range on which OS can open any port specified by ephemeral port range.

If one process is inserting data into your MySQL database? How will you check how many rows inserted into every second? Purpose of this Unix Command Interview is asking about "watch" command in UNIX which is repeatedly execute command provided with specified delay. You have a tab separated file which contains Name, Address and Phone Number, list down all Phone Number without there name and Addresses? CUT use tab as default separator so you can use cut -f3 filename. Your application home directory is full?

How will you find which directory is taking how much space?

By using disk usage DU command in Unix for example du —sh. How do you find for how many days your Server is up?

By using uptime command in UNIX You have an IP address in your network how will you find hostname and vice versa? This is a standard UNIX command interview question asked by everybody and I guess everybody knows its answer as well.

These are very basic unix commands and you must know these commands if you are going to appear in a unix interview. I have listed down 31 unix interview questions with answers which cover basic unix commands like ls, banner, cat, date, tee, who, man, head, pg, cmp, diff, grep, kill, echo, su etc.

So lets have a look on following unix interview questions and commands. Construct pipes to execute the following jobs. Output of who should be displayed on the screen with value of total number of users who have logged in displayed at the bottom of the list. Contents of file1 and file2 should be displayed on the screen and this output should be appended in a file. Name of cities should be accepted from the keyboard. This list should be combined with the list present in a file.

Explain the following commands. It reads the standard input and sends it to the standard output while redirecting a copy of what it has read to the file specified by the user.

The input from a pipe can be combined with the input from a file. In the above command the output from who becomes the std input to sort , meanwhile sort opens the file logfile, the contents of this file is sorted together with the output of who rep by the hyphen and the sorted output is redirected to the file newfile.

Which of the following commands is not a filter man , b cat , c pg , d head Ans: Explain the steps that a shell follows while processing a command.

After the command line is terminated by the key, the shell goes ahead with processing the command line in one or more passes. The sequence is well defined and assumes the following order. The shell first breaks up the command line into words, using spaces and the delimiters, unless quoted. All consecutive occurrences of a space or tab are replaced here with a single space. Variable evaluation: Command substitution: Any command surrounded by backquotes is executed by the shell which then replaces the standard output of the command into the command line.

Wild-card interpretation: Any word containing a wild-card is replaced by a sorted list of filenames that match the pattern. The list of these filenames then forms the arguments to the command.

PATH evaluation: It finally looks for the PATH variable to determine the sequence of directories it has to search in order to hunt for the command. What difference between cmp and diff commands? It searches for the pattern, specified in the command line with appropriate option, in a file s.

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What is the difference between cat and more command? Cat displays file contents. If the file is large the contents scroll off the screen before we view it. So command 'more' is like a pager which displays the contents page by page. Write a command to kill the last background job?

Which command is used to delete all files in the current directory and all its sub-directories? What will the following command do? Is it possible to create new a file system in UNIX? Is it possible to restrict incoming message? What is the use of the command "ls -x chapter[]" ls stands for list; so it displays the list of the files that starts with 'chapter' with suffix '1' to '5', chapter1, chapter2, and so on. If so, what is its use?

With the help of this command you can find the disk capacity and free space of the disk. Is it possible to count number char, line in a file; if so, How? Yes, wc-stands for word count. Name the data structure used to maintain file identification? How many prompts are available in a UNIX system?

How does the kernel differentiate device files and ordinary files?

Kernel checks 'type' field in the file's inode structure. How to switch to a super user status to gain privileges? The system asks for password and when valid entry is made the user gains super user admin privileges.

What are shell variables? Shell variables are special variables, a name-value pair created and maintained by the shell. What is redirection? Directing the flow of data to the file or from the file for input or output. How to terminate a process which is running and the specialty on command kill 0?

With the help of kill command we can terminate the process. What is a pipe and give an example? A pipe is two or more commands separated by pipe char ' '. That tells the shell to arrange for the output of the preceding command to be passed as input to the following command.

When a sequence of commands are combined using pipe, then it is called pipeline. Explain kill and its possible return values. There are four possible results from this call: This implies that a process exists with the given PID, and the system would allow you to send signals to it. It is system-dependent whether the process could be a zombie. On some systems, the process could be a zombie. This means that either the process exists again, it could be a zombie or draconian security enhancements are present e.

What is relative path and absolute path. Absolute path: Exact path from root directory. Relative path: Relative to the current path. How are devices represented in UNIX? 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.

A 'block special file' represents a device with characteristics similar to a disk data transfer in terms of blocks. A 'character special file' represents a device with characteristics similar to a keyboard data transfer is by stream of bits in sequential order.

What is 'inode'? All UNIX files have its description stored in a structure called 'inode'. The inode contains info about the file-size, its location, time of last access, time of last modification, permission and so on. Directories are also represented as files and have an associated inode.

In addition to descriptions about the file, the inode contains pointers to the data blocks of the file. If the file is large, inode has indirect pointer to a block of pointers to additional data blocks this further aggregates for larger files. A block is typically 8k. Inode consists of the following fields: File owner identifier File type File access permissions File access times Number of links File size Location of the file data Brief about the directory representation in UNIX A Unix directory is a file containing a correspondence between filenames and inodes.

A directory is a special file that the kernel maintains. Only kernel modifies directories, but processes can read directories. The contents of a directory are a list of filename and inode number pairs.

When new directories are created, kernel makes two entries named '. System call for creating directory is mkdir pathname, mode. How do you change File Access Permissions? Every file has following attributes: Example 1: To change mode of myfile to 'rw-rw-r--' ie. Example 2: To change mode of myfile to 'rwxr--r--' we give the args as: What are links and symbolic links in UNIX file system?

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

Symbolic link 'is' a file that only contains the name of another file. Operation on the symbolic link is directed to the file pointed by the it.

Both the limitations of links are eliminated in symbolic links. Commands for linking files are: FIFO are otherwise called as 'named pipes'.

FIFO first-in-first-out is a special file which is said to be data transient. Once data is read from named pipe, it cannot be read again. Also, data can be read only in the order written.

Standard Input could be text typed on the keyboard, input from other file or output of other file serving as input. Standard output is y default the display screen.

The most popular example of Unix filter id grep command. This program look for a certain pattern in a file or list of files and only those lines are displayed on the output screen which contains the given pattern. Q 49 Write a command to erase all files in the current directory including all its subdirectories. Q 50 What do understand by Kernel? Unix operating system is basically divided into three parts, namely, the kernel, the shell and the commands and utilities.

Kernel serves as the heart of the Unix operating system which does not deal directly with the user but rather act as a separate interactive program for users logged in.

It performs the following functions: a Interacts with the hardware b Perform tasks like memory management, file management and task scheduling. Q 51 Describe key features of Bourne shell.

Bourne shell is referred to as the standard shell. Q 52 Enlist the key features of Korn Shell.

General UNIX interview questions with answers

The Korn shell is the most advanced as well as an extension to the Bourne Shell which is backward- compatible. Some of the features of Korn shell are listed below: a Perform command line editing.

Q 53 What do you understand by shell variables? A variable is defined as a character string to which a value is assigned, where values could be the number, text, filename, etc. The shell maintains the set of internal variables as well as enables deletion, assignment, and the creation of variables. Thus the shell variables are a combination of identifiers and assigned values that exist within the shell.

These variables are local to the shell in which they are defined as well as they work in a particular way. They may have default value or values can be assigned manually by using appropriate assignment command. Q 54 Describe responsibilities of Shell in brief. Apart from analyzing the input line as well as initiating the execution of the program entered by the user, Shell also serves various responsibilities. Find below a brief description: a The shell is responsible for the execution of all the programs by analyzing the line and determining the steps to be performed and then initiate the execution of the selected program.

It also performs Filename substitution. This file system consists of the files that are organized into a multi-level hierarchy called a directory tree. Command substitution is the method which is performed every time the commands that are enclosed in backquotes are processed y the shell.

Create a read-only file in your home directory? This is a simple UNIX command interview questions where you need to create a file and change its parameter to read- only by using chmod command you can also change your umask to create read only file. How will you find which operating system your system is running on in UNIX? By using command "uname -a" in UNIX 4. How will you run a process in background? How will you bring that into foreground and how will you kill that process?

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 questions because many of programmer not familiar with background process in UNIX. How do you know if a remote host is alive or not?

You can check these by using either ping or telnet command in UNIX. This question is most asked in various Unix command Interview because its most basic networking test anybody wants to do it.

How do you see command line history in UNIX? Very useful indeed, use history command along with grep command in unix to find any relevant command you have already executed. How do you copy file from one host to other? Many options but you can say by using "scp" command. You can also use rsync command to answer this UNIX interview question or even sftp would be ok. How do you find which process is taking how much CPU?

By using "top" command in UNIX, there could be multiple follow-up UNIX command interview questions based upon response of this because TOP command has various interactive options to sort result based upon various parameter. How do you check how much space left in current drive? By using "df" command in UNIX. For example "df -h. This is part of anyone day to day activity so I think this Unix Interview question will be to check anyone who claims to working in UNIX but not really working on it.

TOP 70+ Best UNIX Interview Questions with Answers

What is the difference between Swapping and Paging? Whole process is moved from the swap device to the main memory for execution. Process size must be less than or equal to the available main memory.

It is easier to implementation and overhead to the system. Swapping systems does not handle the memory more flexibly as compared to the paging systems.Which command is used to delete all files in the current directory and all its sub-directories? Apart from analyzing the input line as well as initiating the execution of the program entered by the user, Shell also serves various responsibilities.

An UNIX process started with nohup will not stop even if the user who has stared log off from system. Download The E-book. What is piping? With the help of this command you can find the disk capacity and free space of the disk.

UNIX interview questions and answers For anyone preparing to attend a UNIX interview, here are some of the few questions you may likely be asked: How do you find a process and kill that? 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. Process before swapping is residing in the primary memory in its original form. So command 'more' is like a pager which displays the contents page by page.

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