Longest and Shortest word in a file C programming - c

Question

Hello and good evening,
So i'm writing a program in C, that will accept a file.txt as an input and read the text. The program should read the text file, find the longest and shortest word within the file, and print them out when it reaches the end.
I'm REALLY close but i'm getting a seg fault and, not only do I not know why, but i'm at a loss as to how to fix it.
Here's the code:
#include <stdio.h>
#include <string.h>
FILE *fp;
char str[60];
char *largest;
char *smallest;
char *word;
int i, j;
int main (int argc, char **argv) {
// check that there are only two arguments
if (argc == 2) {
fp = fopen(argv[1], "r");
}
// if not throw this error
else {
perror("Argument error.");
return (-1);
}
// check if the file exists
if (fp == NULL) {
perror("Error opening file.");
return (-1);
}
// set largest to first string and smallest to second
largest = strcpy(largest, strtok(str, " "));
smallest = strcpy(smallest, strtok(NULL, " "));
word = strcpy(word, strtok(str, " "));
// while we get lines of the file
while (fgets (str, 60, fp) != NULL) {
// while the token string isn't empty
while (word != NULL) {
if (strlen(largest) > strlen(word)) {
strcpy(word, largest);
}
if (strlen(smallest) < strlen(word)) {
strcpy(word, smallest);
}
}
}
printf("The largest word in the file is: %s", largest);
printf("The smallest word in the file is: %s", smallest);
fclose(fp);
return 0;
}
I'm pretty sure it's the second while loop...I don't want to use it anyway, but i've been hacking at this for so long it's all my logic can think of.
Any help would be appreciated. This IS homework, though only a small part of it, and i'm not asking for helping solving the entire problem.
Also, there is a Makefile involved...I don't think it's important post but feel free to ask me and i'll update.
As I built this I can confirm that the file is able to read and I can print, put, and do all kinds of cool things. It only broke when I tried to implement my logic for longest/shortest word.
Thanks!

Answer 1

There are some problems with your logic. Try the below code
Few assumptions I made are,
Maximum word length is 20 characters. You can change it by MAX_WORD_LENGTH macro.
Words in file are space separated
Max line length is 60 characters
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#define MAX_WORD_LENGTH 20
int main (int argc, char **argv)
{
FILE *fp;
char str[60];
char *largest = (char*) malloc (MAX_WORD_LENGTH);
char *smallest = (char*) malloc (MAX_WORD_LENGTH);
int smallest_len = MAX_WORD_LENGTH, largest_len = 0;
if (argc == 2)
{
fp = fopen(argv[1], "r");
}
else
{
printf("Argument error.");
return (-1);
}
if (fp == NULL)
{
printf("Error opening file.");
return (-1);
}
while (fgets (str, 60, fp) != NULL)
{
char *temp = strtok(str, " ");
while (temp != NULL)
{
if (strlen(temp) > largest_len)
{
strcpy(largest, temp);
largest_len = strlen(largest);
}
if (strlen(temp) < smallest_len)
{
strcpy(smallest, temp);
smallest_len = strlen(smallest);
}
temp = strtok(NULL, " ");
}
}
printf("The largest word in the file is: %s\n", largest);
printf("The smallest word in the file is: %s\n", smallest);
fclose(fp);
return 0;
}

Answer 2

Adopt it for your needs with argv[2]
and enjoy
#include <stdio.h>
#include <string.h>
int main() {
const int max_word_length = 60;
char longest[max_word_length];
char shortest[max_word_length];
char current[max_word_length];
size_t longest_length = 0;
size_t shortest_length = max_word_length;
size_t current_length = 0;
freopen("input", "r", stdin);
freopen("output", "w", stdout);
while (scanf("%s", current) > 0) {
current_length = strlen(current);
if ( current_length > longest_length) {
longest_length = current_length;
strcpy(longest, current);
}
if (current_length < shortest_length) {
shortest_length = current_length;
strcpy(shortest, current);
}
}
printf("%s %s", shortest, longest);
return 0;
}

Answer 3

So I just ran this online and it looks like the seg fault is caused by the line
largest = strcpy(largest, strtok(str, " "));
This is because largest is the destination of the string copy in the call
strcpy(largest, strtok(str, " "));
but it's a pointer that points to nothing. It should be declared as an actual array like this:
char largest[60];
Also, you shouldn't be calling strtok on a str when it hasn't been initialized to anything. It's not even a proper string so there's no way strtok is going to do anything useful at that point.