osslip3

/*Q.1 Write the simulation program to implement demand paging and show the page
scheduling and total number of page faults according to the LRU (using
counter method) page replacement algorithm. Assume the memory of n
frames.
Reference String : 3,5,7,2,5,1,2,3,1,3,5,3,1,6,2 */
//C program for LRU replacement algorithm implementation

#include <stdio.h>

//user-defined function
int findLRU(int time[], int n)
{
int i, minimum = time[0], pos = 0;

for (i = 1; i < n; ++i)
{
if (time[i] < minimum)
{
minimum = time[i];
pos = i;
}
}

return pos;
}

//main function
int main()
{
int no_of_frames, no_of_pages, frames[10], pages[30], counter = 0, time[10], flag1, flag2, i, j, pos, faults = 0;
printf("Enter number of frames: ");
scanf("%d", &no_of_frames);

printf("Enter number of pages: ");
scanf("%d", &no_of_pages);

printf("Enter reference string: ");

for (i = 0; i < no_of_pages; ++i)
{
scanf("%d", &pages[i]);
}

for (i = 0; i < no_of_frames; ++i)
{
frames[i] = -1;
}

for (i = 0; i < no_of_pages; ++i)
{
flag1 = flag2 = 0;

  for (j = 0; j < no_of_frames; ++j)
  {
     if (frames[j] == pages[i])
     {
        counter++;
        time[j] = counter;
        flag1 = flag2 = 1;
        break;
     }
  }

  if (flag1 == 0)
  {
     for (j = 0; j < no_of_frames; ++j)
     {
        if (frames[j] == -1)
        {
           counter++;
           faults++;
           frames[j] = pages[i];
           time[j] = counter;
           flag2 = 1;
           break;
        }
     }
  }

  if (flag2 == 0)
  {
     pos = findLRU(time, no_of_frames);
     counter++;
     faults++;
     frames[pos] = pages[i];
     time[pos] = counter;
  }

  printf("\n");

  for (j = 0; j < no_of_frames; ++j)
  {
     printf("%d\t", frames[j]);
  }

}

printf("\nTotal Page Faults = %d", faults);

return 0;
}

/*Write a programto implement the toy shell. It should display the command
prompt “myshell$”. Tokenize the command line and execute the given
command by creating the child process. Additionally it should interpret the
following commands.
count c filename :- To print number of characters in the file.
count w filename :- To print number of words in the file.
count l filename :- To print number of lines in the file. */

#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<string.h>
#include<fcntl.h> // open,read(),close() : file related function
void count(char p1,charfname)
{
int handle,ccnt=0,wcnt=0,lcnt=0;
char ch;

handle=open(fname,O_RDONLY);

if(handle==-1)
{
	printf("\n File %s Not Found....",fname);
}
else
{
	while(read(handle,&ch,1))			//on failure read() function returns 0
	{
		if(ch==' '||ch=='\t')
			wcnt++;
		else if(ch=='\n')
		{
			lcnt++;
			wcnt++;
		}
		ccnt++;
	}

	close(handle);

	if(strcmp(p1,"C")==0)
	{
		printf("\nTotal No. of character in file = %d",ccnt);

	}
	else if(strcmp(p1,"W")==0)
	{
		printf("\nTotal No. of words in file = %d",wcnt);
	}
	else if(strcmp(p1,"L")==0)
	{
		printf("\nTotal No. of Lines in file = %d",lcnt);

	}
	else
	{
		printf("\nInvalid Option......\n");
	}
}

}
int main()
{
char cmd[80],tok1[10],tok2[10],tok3[10],tok4[10];
int n;
while(1)
{
printf("\nMYSHELL $]");

            fgets(cmd,80,stdin);

            n=sscanf(cmd,"%s%s%s%s",tok1,tok2,tok3,tok4);   //n=no of tokens are formed from given command

            switch(n)
            {
                    case 1:

                            if(fork()==0)
                            {
                                    execlp(tok1,tok1,NULL); //paramenters- nameOfProcess,parametersOfProcess        
                            }
                            wait(0);
                            break;
                    case 2 :
                            if(fork()==0)
                            {
                                    execlp(tok1,tok1,tok2,NULL);
                            }
                            wait(0);
                            break;
                    case 3:
							if(strcmp(tok1,"count")==0)
							{
								count(tok2,tok3);
							}
							else
							{
                            	if(fork()==0)
                            	{
                                    	execlp(tok1,tok1,tok2,tok3,NULL);
                            	}
                            	wait(0);
							}
                            break;
                    case 4 :
                            if(fork()==0)
                            {
                                    execlp(tok1,tok1,tok2,tok3,tok4,NULL);
                            }
                            wait(0);
                            break;

            }
    }

}