osslip9

/*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 : 2, 4, 5, 6, 9, 4, 7, 3, 4, 5, 6, 7, 2, 4, 7, 1
*/

#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 programto implement the shell. It should display the command prompt
“myshell$”. Tokenize the command line and execute the given command by creating the child process. Additionally it should interpret the following commands. myshell$ search f filename pattern :- To display first occurrence of
pattern in the file.
myshell$ search a filename pattern :- To search all the occurrence of
pattern in the file.
*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<unistd.h>
#include<string.h>
#include<fcntl.h> // open,read(),close() : file related function
void search(char *p1,char pat,charfname)
{
int handle,i=0,cnt=0;
char ch,data[100],*ptr;

handle=open(fname,O_RDONLY);

if(handle==-1)
{
	printf("\n File %s Not Found....",fname);
}
else
{
	if(strcmp(p1,"F")==0)
	{	
		i=0;
		while(read(handle,&ch,1))			//on failure read() function returns 0
		{
			data[i]=ch;
			i++;
			if(ch=='\n')
			{
				data[i]='\0';
				if(strstr(data,pat)!=NULL)
				{
					printf("\nFIRST OCCURANCE OF PATTERN IN LINE IS GIVEN BELOW\n");
					puts(data);
					break;
				}
				i=0;
			}
		}
		close(handle);
	}
	else if(strcmp(p1,"C")==0)
	{
		cnt=0;
		i=0;
                    while(read(handle,&ch,1))                       //on failure read() function returns 0
                    {
                            data[i]=ch;
                            i++;
                            if(ch=='\n')
                            {
                                    data[i]='\0';
                                    ptr=data;
                                    while((ptr=strstr(ptr,pat))!=NULL)
                                    {
				                     	cnt++;
					                    ptr++;
                                    }

				                    i=0;
                            }
                    }
		printf("\nNo of occurances of '%s' = %d",pat,cnt);
                    close(handle);
	}
	else if(strcmp(p1,"A")==0)
	{
		 printf("\nDispaying All Occurances of '%s'\n",pat);
                    i=0;
                    while(read(handle,&ch,1))                       //on failure read() function returns 0
                    {
                            data[i]=ch;
                            i++;
                            if(ch=='\n')
                            {
                                    data[i]='\0';

                                    if((ptr=strstr(data,pat))!=NULL)
                                    {
                                            puts(data);

                                    }
				i=0;
                            }
                    }
	}

}//else

}
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(fork()==0)
                            {
                                   	execlp(tok1,tok1,tok2,tok3,NULL);
                            }
                            wait(0);
                            break;
                    case 4 :
			if(strcmp(tok1,"search")==0)
			{
				search(tok2,tok3,tok4);
			}
			else
			{
                            	if(fork()==0)
                            	{
                                    	execlp(tok1,tok1,tok2,tok3,tok4,NULL);
                            	}
                            	wait(0);
			}
                            break;

            }
    }

}