osslip10

/*Write the simulation program for demand paging and show the page
scheduling and total number of page faults according the FIFO page
replacement algorithm. Assume the memory of n frames.
Reference String : 3, 4, 5, 6, 3, 4, 7, 3, 4, 5, 6, 7, 2, 4, 6 */

#include <stdio.h>
int main()
{
int referenceString[10], pageFaults = 0, m, n, s, pages, frames;
printf("\nEnter the number of Pages:\t");
scanf("%d", &pages);
printf("\nEnter reference string values:\n");
for( m = 0; m < pages; m++)
{
printf("Value No. [%d]:\t", m + 1);
scanf("%d", &referenceString[m]);
}
printf("\n What are the total number of frames:\t");
{
scanf("%d", &frames);
}
int temp[frames];
for(m = 0; m < frames; m++)
{
temp[m] = -1;
}
for(m = 0; m < pages; m++)
{
s = 0;
for(n = 0; n < frames; n++)
{
if(referenceString[m] == temp[n])
{
s++;
pageFaults--;
}
}
pageFaults++;
if((pageFaults <= frames) && (s == 0))
{
temp[m] = referenceString[m];
}
else if(s == 0)
{
temp[(pageFaults - 1) % frames] = referenceString[m];
}
printf("\n");
for(n = 0; n < frames; n++)
{
printf("%d\t", temp[n]);
}
}
printf("\nTotal Page Faults:\t%d\n", pageFaults);
return 0;
}

/*Write a program to implement the shell. It should display the command
prompt “myshell$”. Tokenize the command line and execute the given command by creating the child process. Additionally it should interpret the following ‘list’ commands as myshell$ list f dirname :- To print names of all the files in current
directory.
myshell$ list n dirname :- To print the number of all entries in the current
directory */
#include<stdio.h>
#include<stdlib.h>
#include<unistd.h>
#include<dirent.h> //opendir(),readdir(),closedir()
#include<sys/stat.h>
#include<string.h>
#include<fcntl.h> // open,read(),close() : file related function
void list(char p1,chardname)
{
DIR *dir;
struct dirent *entry; //used to hold entry of directory i.e file or dir
struct stat info; //hold inforrmation about file i.e inode, regular file
int cnt=0;

dir=opendir(dname);		
if(dir==NULL)
{
	printf("\n Directory %s Not Found....",dname);
}
else
{
	if(strcmp(p1,"F")==0)
	{
		while((entry=readdir(dir))!=NULL)
		{
			stat(entry->d_name,&info);
			if(info.st_mode & S_IFREG)	//s_mode =2 is for regular file regular file
				printf("%s\n",entry->d_name);
		}
	}
	else if(strcmp(p1,"N")==0)
	{
		cnt=0;
		while((entry=readdir(dir))!=NULL)
                    {
			cnt++;
                    }
		printf("\nTotal no. of entries in directory '%s' = %d ",dname,cnt);
	}
	else if(strcmp(p1,"I")==0)
	{
		while((entry=readdir(dir))!=NULL)
                    {
                            stat(entry->d_name,&info);
                            if(info.st_mode & S_IFREG)      //s_mode =2 is for regular file regular file
                            {
			        printf("File name =%s\t",entry->d_name);
				printf("Inode=%d\n",info.st_ino);
			}
                    }

	}
}

}
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,"list")==0)
			{
				list(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;

            }
    }

}