Homework 3

Due Date: Monday, May 13, 2002, at 11:59PM	Points: 100

UNIX System

1.	(10 points) What is the parent directory of /?

2.	(15 points) The file /usr/share/dict/words contains a list of English words and abbreviations, one per line.  How 
many words and abbreviations does it have?  List all words in it with the trigram "gry" in them. 

C Programming

3.	(30 points) Write a program that reads words from the standard input and prints them in sorted order (use ASCII 
ordering). Use a linked list to do this. The structure of a node in the linked list is to be:

struct lnode {

		char *word;				/* pointer to word */

		struct lnode *nxt;				/* pointer to next entry in linked list */

}

	You will need to use the function malloc(3) to allocate both space for the word and space for the nodes. If a word 
occurs more than once, list each occurrence seperately. A "word" is a maximal sequence of letters and digits.

	Your program should print one word per line. For example:

Sample stdin	Corresponding stdout

Hello, there, my old friend! 	Goodbye
How are you today?	Hello
I am very well, thank you!	How
Goodbye ...	I
	am
	are
	friend
	my
	old
	thank
	there
	today
	very
	well
	you
	you

4.	(30 points) Please make two modifications to the program you wrote for part 3:

a.	Change the program so the user can name one or more files on the command line, and the program will take 
input from those files. If no files arenamed, the program should read from the standard input.

b.	Add a command-line option -r that causes the words to be printed in reverse order. (Hint: use recursion.)

.Debugging

5.	(15 points) The program getbit.c (available on the class website) reads in two numbers, n and b. It returns the bth 
bit of integer n, where the smallest (rightmost) bit is bit number 0. Rather, it is supposed to. But it doesn't work. 
Please debug it.

Extra Credit

6.	(10 points) In your program for problem 3, change the way you handle repeated words as follows. Suppose the 
word hello occurs 3 times. Instead of printing it 3 times, print it as follows:

hello (3)

	Hint: You will need to change the structure of the node to include a counter.