Basic CS-Operating System [3i Infotech Placement]: Sample Questions 29 - 30 of 89

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Question 29

Operating System

Question

MCQ▾

The command “grep first second third/usr/you/myfile”

Choices

Choice (4)

a.

prints lines containing the words first, second or third from the file/usr/you/myfile

b.

searches for lines containing the pattern first in the files second, third, and/usr/you/myfile and prints them

c.

replaces the word first with the word second in the files third and/usr/you/myfile

d.

searches the files/usr/you/myfile and third for lines containing the words first or second and prints

Answer

b.

Explanation

  • The command grep first second third/usr/you/myfile searches for lines containing the pattern first in the files second, third, and/usr/you/myfile and prints them.
  • The grep searches a file for a particular pattern of characters and displays all lines that contain that pattern.
  • The pattern searched in the file is referred as the regular expression.
  • Output line longer than terminal width wraps around to the following lines, but this output corresponds to exactly one line in FILE.

Syntax

grep [optionas] pattern [files]

grep [options] [-e pattern |-f file] [file … .]

Question 30

Operating System
Edit

Describe in Detail

Essay▾

What are the possible states a thread can have?

Explanation

A thread can be in one of the following states:

Define Thread State
  • Ready:
    • Waiting to execute.
    • Dispatcher considers only the pool of threads in ready state.
  • Standby:
    • Select to run next on a particular processor.
    • When correct condition exists, the dispatcher performs a context switch to the new thread.
    • Only one thread is in standby state for the processor on the system.
  • Running:
    • Dispatcher performs a context switch to a thread.
    • Thread enters the running state and executes.
    • Pre-empted a higher priority thread.
  • Waiting:
    • Thread waits for some IO, or synchronize event.
    • Thread can wait on environment subsystem or OS can direct the thread to suspend itself.
    • If the waiting event happens, depending on the priority, the waiting thread moves back to the ready state.
  • Transition:
    • A thread enters the transition state when it is ready for execution but kernel stack is paged out of memory.
    • When kernel stack is brought into memory, the thread enters the ready state.
  • Terminated:
    • When a thread finishes executing, it enters the terminated state.

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