Using fgets and strtok to read in data and create linked list - linked-list

Question

Need some help with reading in lines of data from a text file using the fgets and string tokenization commands, which will then be used to create a linked list. I've followed some examples I've found on Stack Overflow and other tutorial websites, but still cannot get the read function below to work properly in my program, it just causes it to crash. The data file has lines like this:
Zucchini, Squash, pound, 2.19, 45
Yellow, Squash, pound, 1.79, 15
Based on everything I've read, I believe I have the necessary code, but obviously I'm missing something. Also, I commented out one of the fields (the one for float price) as I'm not sure what to use to copy the float value from the data, as I cannot treat it as a string (the integer value right below it seems to let me get away with it in my compiler).
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
// Struct for linked list node
struct produceItem
{
char produce[20];
char type[20];
char soldBy[20];
float price;
int quantityInStock;
struct produceItem *next;
};
// Function to read in data from file to
void read(struct produceItem **head)
{
struct produceItem *temp = NULL;
struct produceItem *right = NULL;
//char ch[3];
char line[50];
char *value;
FILE *data = fopen("RecitationFiveInput.txt", "r");
printf("Trying to open file RecitationFiveInput.txt\n");
if (data == NULL)
{
printf("Could not open file RecitationFiveInput.txt\n");
}
else
{
while(fgets(line, sizeof(line), data))
{
value = strtok(line, ", ");
strcpy(temp->produce, strdup(value));
value = strtok(NULL, ", ");
strcpy(temp->type, strdup(value));
value = strtok(NULL, ", ");
strcpy(temp->soldBy, strdup(value));
//value = strtok(NULL, ", ");
//strcpy(temp->price, strdup(value));
value = strtok(NULL, " \n");
strcpy(temp->quantityInStock, strdup(value));
temp->next = NULL;
if (*head == NULL)
{
*head = temp;
}
else
{
right = *head;
while(right->next != NULL)
{
right = right->next;
}
right->next = temp;
}
}
printf("Successfully opened file RecitationFiveInput.txt\n");
}
fclose(data);
return;
}
// Function to display the nodes of the linked list that contains the data from the data file
void display(struct produceItem *head)
{
int value = 1;
struct produceItem *temp = NULL;
temp = head;
printf("=============================================================================\n");
printf(" Item # Produce Type Sold By Price In Stock\n");
printf("=============================================================================\n");
if(temp == NULL)
{
return;
}
else
{
while(temp != NULL)
{
printf(" %d %s %s %s %lf %d\n", value, temp->produce, temp->type, temp->soldBy, temp->price, temp->quantityInStock);
value++;
temp = temp->next;
if(temp == NULL)
{
break;
}
}
}
return;
}
//Main function
int main()
{
int input = 0;
struct produceItem *head = NULL;
while(1)
{
printf("\nList Operations\n");
printf("=================\n");
printf("1. Stock Produce Department\n");
printf("2. Display Produce Inventory\n");
printf("3. Reverse Order of Produce Inventory\n");
printf("4. Export Produce Inventory\n");
printf("5. Exit Program\n");
printf("Enter your choice: ");
if(scanf("%d", &input) <= 0)
{
printf("Enter only an integer.\n");
exit(0);
}
else
{
switch(input)
{
case 1:
read(&head);
break;
case 2:
display(head);
break;
case 3:
//function
break;
case 4:
//function
break;
case 5:
printf("You have exited the program, Goodbye!\n");
return 0;
break;
default:
printf("Invalid option.\n");
}
}
}
return 0;
}

Answer 1

Never mind everyone, found the issue. The crashes were due to me not allocating memory for the temp pointer in the read me function.