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Frequently Asked UNIX interview questions and answers for freshers

(#M40029552) UNIX QUESTION unix Keep an EYE

Q. What are data structures that are used for Demand Paging?

A. Kernel contains 4 data structures for Demand paging. They are,
Page table entries,
Disk block descriptors,
Page frame data table (pfdata),
Swap-use table.

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(#M40029536) UNIX QUESTION unix Keep an EYE

Q. Is the Process before and after the swap are the same? Give reason.

A. Process before swapping is residing in the primary memory in its original form. The regions (text, data and stack) may not be occupied fully by the process, there may be few empty slots in any of the regions and while swapping Kernel do not bother about the empty slots while swapping the process out.
After swapping the process resides in the swap (secondary memory) device. The regions swapped out will be present but only the occupied region slots but not the empty slots that were present before assigning.
While swapping the process once again into the main memory, the Kernel referring to the Process Memory Map, it assigns the main memory accordingly taking care of the empty slots in the regions.

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(#M40029510) UNIX QUESTION unix Keep an EYE

Q. Discuss the mount and unmount system calls

A. The privileged mount system call is used to attach a file system to a directory of another file system; the unmount system call detaches a file system. When you mount another file system on to your directory, you are essentially splicing one directory tree onto a branch in another directory tree. The first argument to mount call is the mount point, that is , a directory in the current file naming system. The second argument is the file system to mount to that point. When you insert a cdrom to your unix system's drive, the file system in the cdrom automatically mounts to /dev/cdrom in your system.

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(#M40029516) UNIX QUESTION unix Keep an EYE

Q. Predict the output of the following program code

A.
main()
{
fork();
printf("Hello World!");
}
Answer:
Hello World!Hello World!
Explanation:
The fork creates a child that is a duplicate of the parent process. The child begins from the fork().All the statements after the call to fork() will be executed twice.(once by the parent process and other by child). The statement before fork() is executed only by the parent process.

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(#M40029517) UNIX QUESTION unix Keep an EYE

Q. How can you get/set an environment variable from a program?

A. Getting the value of an environment variable is done by using `getenv()'.
Setting the value of an environment variable is done by using `putenv()'.

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(#M40156193) UNIX QUESTION user password identification Keep an EYE

how can we see the password of other users in the machine as a root user?
how can we do this

Asked In UNIX vinu (7 years ago)

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(#M40156294) UNIX QUESTION touch command in unix Keep an EYE

Why do we use touch command in UNIX?
[1] to create an empty file
[2] to rename a file
[3] both
[4] none

Asked In UNIX Rishikesh Agrawani (7 years ago)

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(#M40155923) UNIX QUESTION UNIX command : cat Keep an EYE

The cat command in UNIX is used for

[1] displaying the contents of file
[2] concatenate two files
[3] creating a new file
[4] 1 & 3 both
[5] None

Asked In UNIX Rishikesh Agrawani (7 years ago)

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(#M40156293) UNIX QUESTION sed command in unix Keep an EYE

Why do we use sed command in UNIX?
[1] for replacing any text with another text
[2] for deleting file
[3] for creating directory
[4] None of above

Asked In UNIX Rishikesh Agrawani (7 years ago)

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(#M40029566) UNIX QUESTION unix Keep an EYE

Q. At what mode the fault handler executes?

A. At the Kernel Mode.

Asked In UNIX MAN (10 years ago)

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