Homework 3

Due: November 8, 2019
Points: 100

UNIX/Linux Questions

Please put the answers to these two questions in a text file called linux.txt or a PDF file called linux.pdf.

1. (10 points) What Linux program could I use to generate a random number?
2. (10 points) What is the name of the process with PID 4?

C Programming

3. (30 points) Write a program to search for words in a file. Your program is to work like this.

   First, read in a file of no more than 1000 words (called a dictionary), and store them in a list. This is to be a list of character pointers, each pointing to a word. You will have to use malloc(3), which allocates space dynamically. Each line, including the last, will be ended with a newline, and no line will be over 1024 characters.

   Then, read a second file. This file is also a list of words. Search your list for each word, and for each word print the number of words checked before you either get a match or find it is not in the list. For letters, the case must match (so “N” does not match “n”). Also, after you have finished searching for the words, print the average number of words checked.

   The two files are given as command-line arguments to your program. The first argument is the dictionary, and the second is the list of words to be found.

   To turn in: Put this program into a file called lookup.c; turn it in as directed below.

4. (30 points) Now we will do the next step in the Game of Life program we began in Homework 2. For reference, the program life.c in the directory /home/bishop/hw3-programs draws a board. You can use that, or the one you did for homework 2.

   The next step is to load a predefined pattern onto the board for the game. The predefined pattern is in a file. That file contains rows of “X”s and “O”s (the characters “X” and “O”). The “X” corresponds to a populated cell and the “O” to an unpopulated one. Each line in that file should have the same number of columns. Your program is to read the file, load the configuration into memory, and print it out, properly framed by the board, and stop.

   Your program will take the file with the predetermined pattern as its only argument. It is to print out the board. Note your program will have to count the rows and columns as these will not be given. Report any errors such as a line too long or too short.

   As an example, the inmput file

   XOXXOOXOX
   OOOXXXOOO
   OXOXOXOXO
   XOXOXOXOX
   

   defines a board of 4 rows and 9 columns. It is a valid board. But the board

   OXOXO
   XXXX
   OOOOOO
   

   is not valid as the rows are of different lengths, and the board

   XOXXOOXOX
   OOOXYXOOO
   OXOXOXOXO
   XOXYXOXOX
   

   is not valid because there is a character other than X, O, and newline in the file (specifically, two instances of “Y”). Your program is to report errors in these cases, and then terminate.

   The board dimensions will never be more than 100 rows and 100 columns.

   To turn in: Put this program into a file called life2.c; turn it in as directed below. If you want to submit two files, that is, have this in a separate file, call the main one life2.c and the other file(s) initn.c, where n is a single digit (for example, init0.c). Turn it in as described below.

C Program Debugging

5. (20 points) The program revfile.c, available at /home/bishop/hw3-programs on the CSIF, is to read in up to 1023 lines of input, the maximum input line length being 1023 characters. It will then print the lines in reverse order. But it doesn’t; it crashes. Please identify the problem, and say how to fix it. Give the specific line(s) where the problem arises, and the code that you would fix it with.

   To turn in: Fix the bug and say what you did in a comment at the beginning of the file. Turn in the fixed file as described below.

Extra Credit

6. (10 points) Take the program you wrote for problem 3. Once you have read in the word list from the dictionary, sort the words (you an do this yourself or use the library function qsort(3). Then proceed as in problem 3. So, you will read a second file, search the list for each word in the file, and for each word print the number of words checked before you either get a match or find it is not in the list. Also, after you have finished searching for the words, print the average number of words checked.

   To turn in: Put this program into a file called lookups.c; turn it in as described below.

Turning In Your Homework

For this assignment, you are to create a tar(1) archive and a Makefile.

The Makefile is to have 3 or 4 targets: lookup, life2, revfile, and (if you do the extra credit) lookups. So, when I type make lookup, the Makefile will execute the command to compile your lookup.c program, and save the executable as lookup.

Put the answers to the Linux questions (in a text or PDF file), the Makefile and the programs you wrote into a directory called hw3-ans. Next, create a tar archive:

tar cvf hw3-ans.tar hw3-ans

Matt Bishop Office: 2209 Watershed Sciences Phone: +1 (530) 752-8060 Email: mabishop@ucdavis.edu

ECS 36A, Programming and Problem Solving Version of October 30, 2019 at 8:18PM

You can also obtain a PDF version of this.