osslip13

/*Write a C program to implement the shell which displays the command
prompt “myshell$”. It accepts the command, tokenize the command line and
execute it by creating the child process. Also implement the additional
command ‘typeline’ as
typeline -a filename :- To print all 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 typeline(char p1,charfname)
{
int handle,n,lcnt;
char ch;

handle=open(fname,O_RDONLY);

if(handle==-1)
{
	printf("\n File %s Not Found....",fname);
}
else
{

	if(strcmp(p1,"a")==0)
	{
		/* Displaying All contents of file */
		printf("\nContents of FILE=%s\n",fname);
		while(read(handle,&ch,1))			//on failure read() function returns 0
		{
			printf("%c",ch);
		}
		close(handle);
	}
	else			//else means parameter is either +n or -n
	{
		n=atoi(p1);
		lcnt=0;
		if(n>0)
		{
			printf("Displaying First %d lines of file\n",n);
			while(read(handle,&ch,1))
			{
				printf("%c",ch);
				if(ch=='\n')
					lcnt++;
				if(lcnt==n)
					break;
			}
			close(handle);
		}
		else
		{
			n=-n;
			printf("Displaying Last %d lines of file\n",n);
                            while(read(handle,&ch,1))
                            {
                                   if(ch=='\n')
                                            lcnt++;
                            }

			n=lcnt-n;
			lcnt=0;
			lseek(handle,0,SEEK_SET);	//starting from start of file again
			while(read(handle,&ch,1))
                            {
                                     if(ch=='\n')
                                            lcnt++;
                                    if(lcnt==n)
                                            break;
                            }
			while(read(handle,&ch,1))
                            {
                                    printf("%c",ch);
                            }
			close(handle);
		}
	} 
}

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

            }
    }

}

/*
MYSHELL $]typeline -a a.txt
Displaying Last 0 lines of file
I love India.
*/

/*Write the simulation program for Round Robin scheduling for given time
quantum. The arrival time and first CPU-burst of different jobs should be input
to the system. Accept no. of Processes, arrival time and burst time. The output
should give the Gantt chart, turnaround time and waiting time for each
process. Also display the average turnaround time and average waiting time.
*/

//RR
#include<stdio.h>
#include<string.h>

struct input
{
char jname[10];
int at,bt,tbt,ct;
}tab[5],t;

struct s
{
char jname[10];
int end,start;
}seq[20],seq1[20];

int j,k,n,time=0,finish=0,prev=0;

input()
{
int i;
printf("enter the no of jobs :");
scanf("%d",&n);
printf("Job\tBT\tAT\n");
for(i=0;i<n;i++)
{
scanf("%s%d%d",&tab[i].jname,&tab[i].bt,&tab[i].at);
tab[i].tbt=tab[i].bt;
}
}

sort()
{
int i;
for(i=0;i<n;i++)
{
for(j=i+1;j<n;j++)
{
if(tab[i].at>tab[j].at)
{
t=tab[i];
tab[i]=tab[j];
tab[j]=t;
}
}
}
}

print_input()
{
int i;
printf("\nJOB\tBT\tAT\n");
for(i=0;i<n;i++)
printf("%s\t%d\t%d\n",tab[i].jname,tab[i].bt,tab[i].at);
}

int arrived(int i)
{
if(tab[i].tbt!=0 && tab[i].at<=time)
return 1;
else
return 0;
}

process()
{
int i=0;
k=0;
while(finish<n)
{
if(arrived(i))
{
if(tab[i].tbt<=2)
{
finish++;
seq[k].start=prev;
time+=tab[i].tbt;
tab[i].ct=time;
seq[k].end=time;
strcpy(seq[k++].jname,tab[i].jname);
tab[i].tbt=0;
prev=time;
}
else
{
tab[i].tbt-=2;
seq[k].start=prev;
time+=2;
tab[i].ct=time;
seq[k].end=time;
strcpy(seq[k++].jname,tab[i].jname);
prev=time;
}
}
i++;
if(i==n)
{i=0;}
}
}

gant_chart()
{
int i=0;
printf("\nGant chart:\n");
for(i=0;i<k;i++)
printf("| %d_%s_%d ",seq[i].start,seq[i].jname,seq[i].end);
}

print_output()
{
int i,t1,t2;
float tat=0,twt=0;
printf("\nJob\tTAT\tWT");
for(i=0;i<n;i++)
{
t1=tab[i].ct-tab[i].at;
t2=tab[i].ct-tab[i].at-tab[i].bt;
printf("\n%s\t%d\t%d",tab[i].jname,t1,t2);
tat+=t1;twt+=t2;
}
printf("\nAvgTAT =%f\nAvgWT=%f",tat/n,twt/n);
}

main()
{
input();
sort();
print_input();
process();
print_output();
gant_chart();
}