Exercise 3 Linked Lists, File I/O and More

NWEN 241 Exercise 3
Linked Lists, File I/O and More

Objective:
The objective of this exercise is to write and debug programs using linked lists, file stream
input/output, and command-line arguments.
At the end of this exercise, you should submit the required files to the Assessment System
(https://apps.ecs.vuw.ac.nz/submit/NWEN241/Exercise_3) on or before the
submission deadline. You may submit as many times as you like in order to improve your
mark before the final deadline. Submissions beyond the deadline will not be marked and
will receive 0 marks.
Exercise Requirements
For NWEN 241, it is highly recommended that you undertake all development using the
computers in CO246. The computers in this lab use the Linux operating system. This
guide is written with the assumption that you are in CO246 lab.
If you are not able to go the lab, you can remotely access similar computers via secure
shell (ssh). Consult one of the remote study guides (see https://ecs.wgtn.ac.nz/
Courses/NWEN241_2023T1/RemoteStudyGuides) and follow one that suits you the
most.
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NWEN 241 2023-T1 Linked Lists, File I/O and More Exercise 3
Exercises
You may download a copy of the base source files used in the activities from
https://ecs.wgtn.ac.nz/foswiki/pub/Courses/NWEN241_2023T1/
Exercises/nwen241_exercise3_files.zip.
Activity 1: Linked List [30 Marks]
Copy and paste the following C program1
to your favorite text editor:
1 #include <stdio.h>
2
3 // (1) Complete linked list node declaration below.
4 // Do not change the name of the structure.
5 struct node {
6
7 };
8
9 int main(void)
10 {
11 struct node *head = NULL; // head points to the head of list
12 struct node *tmp;
13
14 // This for-loop will build a list
15 for(int i = 0; i < 10; i++) {
16 // (2) Use malloc() or calloc() to allocate memory for one node
17 // and let tmp point the the allocated memory.
18
19 // (3) Assign 100*(i+1) to data and let next point to NULL.
20
21 // (4) Append tmp to the list pointed by head
22 }
23
24 struct node *rover = head;
25 while(rover) {
26 printf("%d ", rover->data);
27 rover = rover->next;
28 }
29 printf("\n");
30
31 return 0;
32 }
1You can extract a copy of this file from https://ecs.wgtn.ac.nz/foswiki/pub/Courses/
NWEN241_2023T1/Exercises/nwen241_exercise3_files.zip.
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NWEN 241 2023-T1 Linked Lists, File I/O and More Exercise 3
Save the file as activity1.c. Study the source file and do the following within the file:
1. Define a structure named node to represent a singly linked list node. The structure
should have two parameters
• data: an integer
• next: pointer to next node in the list
2. Use either malloc() or calloc() to allocate memory for one node and let tmp
point the the allocated memory.
3. Assign 100*(i+1) to the data member of the node and let the next member point
to NULL.
4. Append the newly created node pointed by tmp to the list pointed by head.
(Append means insert after the current last element in the list.)
Your program should not output anything aside from the output generated by printf()
in lines 26 and 29.
Compile and run the program. If you are happy with the program, submit it to the
Assessment System for marking.
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NWEN 241 2023-T1 Linked Lists, File I/O and More Exercise 3
Activity 2: Text File Processing 2 [30 Marks]
In this activity, you will perform simple text file processing using file stream I/O. Suppose
you are given a text file named raw.txt which contains 2 decimal numbers per line:
12 134
100 94
23 324
10 45
Copy and paste the following C program2
to your favorite text editor:
1 #include <stdio.h>
2
3 int main(void)
4 {
5 int a, b;
6 FILE *in; // use for handling input file
7 FILE *out; // use for handling output file
8
9 // Open raw.txt for reading
10
11 // Open processed.txt for writing
12
13 // Go thru raw.txt file and generate processed.txt file accordingly
14
15 return 0;
16 }
Save the file as activity2.c. Use activity2.c as a starting point to write a program
that will add the numbers in every line of raw.txt and output the numbers together
with the sum to a file named processed.txt. The contents of processed.txt should
look like this:
12 134 146
100 94 194
23 324 347
10 45 55
You can use the file raw.txt included in the archive
https://ecs.wgtn.ac.nz/foswiki/pub/Courses/NWEN241_2023T1/
Exercises/nwen241_exercise3_files.zip to test your code. If you are happy
with the program, submit it to the Assessment System for marking.
[Hint: If you are using fscanf() to scan the contents of the file, you may want to pay
close attention to its return value.]
2You can extract a copy of this file from https://ecs.wgtn.ac.nz/foswiki/pub/Courses/
NWEN241_2023T1/Exercises/nwen241_exercise3_files.zip.
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NWEN 241 2023-T1 Linked Lists, File I/O and More Exercise 3
Activity 3: Command-Line Arguments [40 Marks]
In this activity, you will write a C program that accepts an arbitrary number of command
line arguments. The program should treat every command line argument (excluding the
program name itself) as an integer. The program should add all the integers and print the
sum to the display. For instance, suppose you compile the program into an executable file
named activity3, then if the program is executed as
./activity3 1 2 3 4 5 6
the output should be
21
If the program is executed as
./activity3
the output should be
0
Save the program as activity3.c. To have an easier time with the auto-marking script,
make sure that the output only consists of the sum followed by a newline character.
If you are happy with the program, submit it to the Assessment System for marking.
[Hint: You may use sscanf() to convert a string to an integer.]
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