Shoppinglist program, structs, malloc() and functions - c

Question

I started with an assignment which should include a program that can add remove print, edit, save list.
I am stuck on the first function that should add an item to my grocery list. As you can see, this function (and all other functions) receives a pointer to a shopping list. This is a pointer to the shopping list defined in main(), and my functions should make changes directly to the shopping list that the argument list is pointing to.
The function should ask the user for a name, amount and unit of an item. It should then place it last in the shopping list. The “length” field should always be containing the index to the last position of the array, so this is where the item should be placed. For instance, length is zero when the list is empty, so the first time this function is called, the item should be placed at index zero in list->itemArray.
This function is also responsible for increasing the length of the list. Since we just added one item, the list is now one item longer. Just remember that it should not be possible to add more than 5 items to the list.
If the user enters a non-positive number for amount, the program should tell the user that the input is invalid and repeat the question until a correct answer has been given.
How should I limit the size list to just 5 products?
#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include "ShoppingList.h"
int main(void)
{
struct ShoppingList shoppingList;
shoppingList.length = 0; // The shopping list is empty at the start
int option;
do
{
printf("\n\nWelcome to the shopping list manager!\n");
printf("=====================================\n\n");
printf("1. Add an item\n");
printf("2. Display the shopping list\n");
printf("3. Remove an item\n");
printf("4. Change an item\n");
printf("5. Save list\n");
printf("6. Load list\n");
printf("7. Exit\n");
printf("What do you want to do? ");
scanf("%d", &option);
switch (option)
{
case 1: addItem(&shoppingList); break;
case 2: printList(&shoppingList); break;
case 3: removeItem(&shoppingList); break;
case 4: editItem(&shoppingList); break;
case 5: saveList(&shoppingList); break;
case 6: loadList(&shoppingList); break;
case 7: break;
default:
printf("Please enter a number between 1 and 7");
}
} while (option != 7);
return 0;
}
#define _CRT_SECURE_NO_WARNINGS
#include"ShoppingList.h"
#include<stdio.h>
#include<stdlib.h> // For malloc() and free()
void addItem(struct ShoppingList* list)
{
list = (struct ShoppingList*)malloc(sizeof(struct ShoppingList) * 5);
printf("Name for product: ");
scanf("%s", list->itemList[list->length].productName);
do
{
printf("Enter the amount: ");
scanf("%f", &list->itemList[list->length].amount);
if (list->itemList[list->length].amount <= 0.0)
{
printf("Input is invalid.\n");
}
} while (list->itemList[list->length].amount <= 0.0);
printf("Enter unit of item: ");
scanf("%s", list->itemList[list->length].unit);
list->length++;
}
void printList(struct ShoppingList *list)
{
int i;
printf("\nName:\tAmount:\tUnit:\n\n");
for (i = 0; i < list->length; i++) {
printf("%s\t%d\t%s\n", list->itemList[i].productName, list->itemList[i].amount, list->itemList[i].unit);
}
printf("\n\n");
}
void editItem(struct ShoppingList *list)
{
}
void removeItem(struct ShoppingList *list)
{
}
void saveList(struct ShoppingList *list)
{
}
void loadList(struct ShoppingList* list)
{
}
#ifndef SHOPPING_LIST_H
#define SHOPPING_LIST_H
// Struct definitions
struct GroceryItem
{
char productName[20];
float amount;
char unit[10];
};
struct ShoppingList
{
int length;
struct GroceryItem itemList[5];
};
// Function declarations
void addItem(struct ShoppingList *list);
void printList(struct ShoppingList *list);
void editItem(struct ShoppingList *list);
void removeItem(struct ShoppingList *list);
void saveList(struct ShoppingList *list);
void loadList(struct ShoppingList* list);
#endif