OS-(I) Assignment 1: Set A- 2)

(2) Write a program that demonstrates the use of nice() system call. After a child process is started using fork(), assign higher priority to the child using nice() system call.

Using nice() system call, we can change the priority of the process in multi-tasking system. The new priority number is added to the already existing value.

int nice(int inc);

nice() adds inc to the nice value. A higher nice value means a lower priority. The range of the nice value is +19 (low priority) to -20 (high priority).

Solution:

#include<stdio.h>

#include<sys/types.h>

void main()

{

    int pid,retnice;

    pid=fork();

    for(i=0;i<5;i++)

           {

        if(pid==0)

        {

            retnice=nice(-5);

      printf("Child gets higher CPU priority %d \n",retnice);

            sleep(1);

        }

        else

        {

            retnice=nice(4);

       printf("Parent gets lower CPU priority %d \n",retnice);

            sleep(1);

        }

    }

}