H
OMEWORK
3 ECS 30-A — S
PRING
2002
Version of April 18, 2002 4:59 pm Page 1 of 2
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
b
th
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.
