Author	: Chirag R. Agarwal
ID		: chirag.agarwalr@gmail.com
Problem	: Wanna be hacker
Site	: http://agarwalchirag.wordpress.com

FILES IN MY FOLDER :

I have two separate folders. One for the program excuted using 'dup' command only and one for the 'pipe' command.

==> Folder 1) dup/ :
	1) dup_main.c :
		It is the main driver file. It further forks all other processes.
	
	2) hack_dup.c :
		It is the implementation file. It has the recursive function 'hack()' that does all the hacking you want.
	
	3) HEADER_DUP.h :
		It is the header file that contains all the variable and function declarations.

	4) check.c :
		It has a function named 'check()' that does the 'ls' and 'grep' executions for every process. It creates two processes, one each for ls and grep. It creates two files 'ls_op.txt' and 'grep_op.txt'. Once the job is done, care has been taken to delete these files without leaving a single trace.
	
	5) Makefile :
		The Makefile.

==> Folder 2) pipes/ :
	1) pipe_main.c :
		It is the main driver file. It further forks all other processes.
	
	2) hack_pipe.c :
		It is the implementation file. It has the recursive function 'hack()' that does all the hacking you want.
	
	3) HEADER_PIPE.h :
		It is the header file that contains all the variable and function declarations.

	5) Makefile :
		The Makefile.

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HOW TO EXECUTE MY PROGRAM ?

1) dup/ :
	Simply in the dup/ folder, type 'make'
	This will compile the process and create and executable named 'dup'

	Now type './dup OS_Marks.txt 2009B4A7606G 42' to execute the program.
	Above, I have mentioned a specific input. You can enter any filename, id and marks as required. 
	Just make sure that the file you want to change exists in the 'Evaluator/' folder in the '/home/USER/' directory

2) pipes/ :
	Simply in the dup/ folder, type 'make'
	This will compile the process and create and executable named 'pipe'

	Now type './pipe OS_Marks.txt 2009B4A7606G 42' to execute the program.
	Above, I have mentioned a specific input. You can enter any filename, id and marks as required. 
	Just make sure that the file you want to change exists in the 'Evaluator/' folder in the '/home/USER/' directory

If you do not enter the arguments, an appropriate error message is displayed on the terminal before exiting.
Nothing is displayed on the terminal on execution as expected. The file to be modified can be check after execution to see the change.

To clean all the extra files created by the program type "make clean" on the terminal.

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STRUCTURE :

I have assumed that your machine has a '/home/USER/' directory which contains contains the user Student and the group 'Evaluator/'.
Thus, I begin my execution from '/home/USER/Evaluator/'directory.

You can change the 'USER' to 'user' if required in the main program. You can search for the line "strcpy(path,"/home/USER/Evaluator/");"

Before executing the hack() function, I initialize the shared memory with a string "start".
Every process will now check if the shared memory variable is "start" or not. If yes, then the required file is not found.
If no, then it doesn't fork any other process and quits.

If a process finds the required file, it appends the Current Path to the shared memory variable and exits.
The main process then reads the path from the shared memory and makes changes to the file as desired.

For pipe :
I have created 3 pipes. 
One to perform 'ls' and pipe to 'grep'.
Other to pipe 'grep' output and read it.
If 'grep' doesn't find the file, another pipe is used to perform 'ls' again and then call the function again for the sub-directories.

NO FILES have been created when using 'pipes' unlike 'dup', as expected.