Unix System : Practice Questions and Answers

Browse topic-based Unix System practice sets.

73 practice sets · Page 1 of 4

Unix SystemHardOperating System Unix System

Which of the following commands is used to remove files from the user file system, with a confirmation prompt, if they have neither been accessed nor modified in the last one year?

find /user/* (-mtime +365 -a -atime +365) -ok rm {} ;

grep (/usr/*) -mtime +365 | -ok rm

find -mtime +365 | rm

find -name -mtime +365 / -ok rm

View Answer

Correct Answer: A — find /user/* (-mtime +365 -a -atime +365) -ok rm {} ;

Explanation:

The find command with -mtime and -atime flags locates files based on modification and access times, and -ok rm {} \; prompts for confirmation before deleting.

Unix SystemMediumOperating System Unix System

Which of the following commands is used to summarize the disk usage?

fdisk

chkdsk

disk

View Answer

Correct Answer: C — du

Explanation:

The du (disk usage) command in UNIX/Linux is used to estimate and summarize file and directory space usage.

Unix SystemMediumOperating System Unix System

Which command is used to sort the lines of data in a file in alphabetical order?

sort

sort -r

View Answer

Correct Answer: C — sort

Explanation:

The sort command arranges the lines of text in alphabetical or numerical order by default.

Unix SystemMediumOperating System Unix System

If a file has read and write permissions for the owner, then the octal representation of the permissions will be

View Answer

Correct Answer: B — 6

Explanation:

In octal permission representation, read is 4 and write is 2, making the combined read and write permission equal to 6.

Unix SystemMediumOperating System Unix System

Which command is used to copy a file named 'wb' from the 'programs' directory to the 'misc' directory while retaining its name?

copy a:programs/wb b:misc/wb

tar programs/wb misc/wb

copy programs/wb misc/wb

cp programs/wb misc

View Answer

Correct Answer: D — cp programs/wb misc

Explanation:

The cp command is used in UNIX/Linux to copy files, and specifying the destination directory (misc) copies the file with the same name.

Unix SystemHardOperating System Unix System

Which is the earliest and most widely used shell that came with the UNIX system?

C shell

Korn shell

Bourne shell

Smith shell

View Answer

Correct Answer: C — Bourne shell

Explanation:

The Bourne shell (sh) is the original and earliest standard shell developed for the UNIX operating system by Stephen Bourne.

Unix SystemMediumOperating System Unix System

What does the seventh field of the /etc/passwd file represent?

home

password

shell

View Answer

Correct Answer: D — shell

Explanation:

The seventh and final field in the /etc/passwd file specifies the default login shell for the user.

Unix SystemHardOperating System Unix System

Which command is used to display the end of the file?

bof

head -r

tail

eof

View Answer

Correct Answer: C — tail

Explanation:

The tail command outputs the last part (end) of files by default.

Unix SystemMediumOperating System Unix System

Which command is used to create a directory?

mkdir

crdir

View Answer

Correct Answer: B — mkdir

Explanation:

The mkdir (make directory) command is used in UNIX-like systems to create new directories.

Unix SystemEasyBasics

10.

Which statement is not correct about the “init” process in Unix?

It is the first process in the system.

It has PID 1.

It is generally the parent of the login shell.

Init forks and execs a ‘getty’ process at every port connected to a terminal.

View Answer

Correct Answer: A — It is the first process in the system.

Explanation:

While init is the first user-level process with PID 1, it is technically preceded by the swapper/sched process (PID 0) which is created by the kernel during boot.

Unix SystemMediumBasics

11.

Unix command to change the case of first three lines of file “shortlist” from lower to upper

$ tr shortlist head -3 '[a-z]' '[A-Z]'

$ head -3 shortlist | tr '[a-z]' '[A-Z]'

$ tr head -3 shortlist '[A-Z]' '[a-z]'

$ tr '[a-z]' '[A-Z]' shortlist | head -3

View Answer

Correct Answer: B — $ head -3 shortlist | tr '[a-z]' '[A-Z]'

Explanation:

The head -3 command extracts the first three lines of the file, which are then piped into the tr command to translate lowercase characters to uppercase.

Unix SystemMediumBasics

12.

Match the following vi commands in Unix:

List-I	List-II
(a) :w	(i) Saves the file and quits editing mode
(b) :x	(ii) Quits without saving
(c) :q	(iii) Saves the file
(d) :q!	(iv) Quits the editor

(a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)

(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

(a)-(ii), (b)-(iii), (c)-(i), (d)-(iv)

(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)

View Answer

Correct Answer: A — (a)-(iii), (b)-(i), (c)-(iv), (d)-(ii)

Explanation:

In the vi text editor, :w writes (saves) the file, :x saves and quits, :q quits the editor, and :q! quits without saving.

Unix SystemEasyBasics

13.

The Unix Operating System Kernel maintains two key data structures related to processes: the process table and the user structure. Consider the following statements:

Statement I: The process table is resident all the time and contains information needed for all processes, even those that are not currently in memory.

Statement II: The user structure is swapped or paged out when its associated process is not in memory, in order not to waste memory on information that is not needed.

Which of the statements given above is/are correct?

Both Statement I and Statement II are correct

Both Statement I and Statement II are incorrect

Only Statement I is correct

Only Statement II is correct

View Answer

Correct Answer: A — Both Statement I and Statement II are correct

Explanation:

The process table resides in memory permanently for process tracking, while the user structure can be swapped out to save memory when a process is not executing.

Unix SystemMediumBasics

14.

Consider the following operations to be performed in Unix:

“The pipe sorts all files in the current directory modified in the month of June by order of size and prints them to the terminal screen. The sort option skips ten fields then sorts the lines in numeric order.”

ls -l | grep "June" | sort +10r

ls -l | grep -n "June" | sort +10x

ls -l | grep -v "June" | sort +10n

ls -l | grep "June" | sort +10n

View Answer

Correct Answer: D — ls -l | grep "June" | sort +10n

Explanation:

The pipeline ls -l | grep "June" | sort +10n lists files, filters for "June", and skips 10 fields to sort numerically by size.

Unix SystemMediumBasics

15.

Consider the following statements regarding the 'nice' command of UNIX:

Statement I: It is used to set or change the priority of a process.

Statement II: A process's nice value can be set at the time of creation.

Statement III: Only the superuser can specify a negative nice value to increase process priority.

Which of the statements given above is/are correct?

Statement II and Statement III only

Statement I and Statement III only

Statement I and Statement II only

Statement I, Statement II, and Statement III

View Answer

Correct Answer: D — Statement I, Statement II, and Statement III

Explanation:

The nice command changes a process's scheduling priority. Users can launch processes with lower priority, but only root (superuser) can assign negative values for higher priority.

Unix SystemMediumBasics

16.

In UNIX, processes that have finished execution but have not yet had their status collected are known as ________.

Zombie Processes

Stopped Processes

Sleeping processes

Orphan Processes

View Answer

Correct Answer: A — Zombie Processes

Explanation:

A zombie process is one that has completed execution but still has an entry in the process table because the parent has not yet read its exit status.

Unix SystemEasyBasics

17.

In UNIX operating system, when a process creates a new process using the fork() system call, which of the following state is shared between the parent process and child process?

Both Heap and Stack

Stack

Heap

Shared memory segments

View Answer

Correct Answer: D — Shared memory segments

Explanation:

While fork() creates a separate address space copying the heap and stack, shared memory segments remain shared between the parent and child processes.

Unix SystemHardBasics

18.

Which of the following information about the UNIX file system is not correct?

Each i-node is 256-bytes long

All the files and directories are stored in data blocks

An i-node contains accounting information as well as enough information to locate all the disk blocks that holds the file’s data.

Super block contains the number of i-nodes, the number of disk blocks, and the start of the list of free disk blocks.

View Answer

Correct Answer: A — Each i-node is 256-bytes long

Explanation:

Traditional UNIX i-nodes are typically 64 or 128 bytes long, not fixed at 256 bytes in all historical implementations.

Unix SystemMediumBasics

19.

Which of the following option with reference to UNIX operating system is not correct?

QUIT is similar to TERM, except that it defaults to producing a core dump if not caught.

KILL is a blockable signal.

INT signal is sent by the terminal driver when one types < Control-C > and it is a request to terminate the current operation.

TERM is a request to terminate execution completely. The receiving process will clean up its state and exit.

View Answer

Correct Answer: B — KILL is a blockable signal.

Explanation:

The SIGKILL (KILL) signal cannot be caught, blocked, or ignored by a process.

Unix SystemMediumBasics

20.

What is the function of following UNIX command?

wc -l < a > b &

It runs the word count program to count the number of lines in its input, a, writing the result to b, as a foreground process.

It runs the word count program to count the number of lines in its input, a, writing the result to b, but does it in the background.

It counts the errors during the execution of a process, a, and puts the result in process b.

It copies the ‘ l ’ numbers of lines of program from file, a, and stores in file b.

View Answer

Correct Answer: B — It runs the word count program to count the number of lines in its input, a, writing the result to b, but does it in the background.

Explanation:

The command wc -l counts the number of lines from input file 'a', redirects the output to file 'b', and the & symbol runs it as a background process.

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List-I

List-II

(a) :w

(i) Saves the file and quits editing mode

(b) :x

(ii) Quits without saving

(iii) Saves the file

(d) :q!

(iv) Quits the editor