My c program keeps crashing on as it's starting

Question

I'm making a c program for a simple library but for some reason the program keeps crashing right on startup. Like there's a menu that is displayed but it doesn't even appear it just crashes. can any one help me?

struct library
{
    char name[50];
    int id;
    int qty;
}books[50],copy[50],delet[50],sort[50];
int i=0;
FILE *mybooks;

int main()
{
    int choice; char ans;
    int id;
    int qty;
    int s,o=0,j=0;
    char name[50];
    mybooks=fopen("D:\\mybooks.txt","r");
    if (mybooks == NULL) printf("Error. File not found.");
    else
    {
        while(!feof(mybooks))
        {
            fscanf(mybooks,"%[^\n] %d %d",books[i].name,&books[i].id,&books[i].qty);
            strcpy(copy[i].name,books[i].name);
            copy[i].id=books[i].id;
            copy[i].qty=books[i].qty;
            i++;
        }
        fclose(mybooks);
    }
    printf("Welcome to the Library.\n");
    do
    {

        printf("Please choose an option:\n");
        printf("1.Insert a book\n");
        printf("2.Delete a book\n");
        printf("3.Search a book by ID\n");
        printf("4.Search a book by name\n");
        printf("5.Display all books (sorted by name)\n");
        printf("6.Display all books (unsorted)\n");
        scanf("%d",&choice);
        switch (choice){
        case 1:
            printf("You will need to enter a name, ID, and quantity of the book.\n");
            printf("please enter book name:");
            fflush(stdin);
            fgets(name,sizeof name,stdin);
            printf("please enter book ID:");
            scanf("%d",&id);
            printf("please enter book quantity:");
            scanf("%d",&qty);
            InsertBook(name,id,qty);
            printf("your book has been added successfully\n");
            break;
        case 2:
            printf("Please enter book ID:");
            scanf("%d",&id);
            DeleteBook(id);
            printf("book successfully deleted.\n");
            break;
        case 3:
            printf("Please enter ID of Book:");
            scanf("%d",&id);
            s=LinearSearch(id,j);
            if (s>=0)
            {
                printf("Book Found.\n");
                printf("Name:%s",books[s].name);
                printf("ID:%d\n",books[s].id);
                printf("Quantity:%d\n",books[s].qty);
            }
            else
                printf("Sorry, the book doesn't exist.\n");
            break;
        case 4:
            printf("Please enter name of book:");
            fflush(stdin);
            gets(name);
            sorting();
            s=BinarySearch(name,0,i);
            printf("Book Found.\n");
            printf("ID:%d\n",sort[s].id);
            printf("Quantity:%d\n",sort[s].qty);
            break;
        case 5:
            sorting();
            while (o<i);
            {
                printf("%s\n",sort[o].name);
                o++;
            }
            printf("\n");
            break;
        case 6:
            while(o<i)
            {
                printf("%s",books[o].name);
                o++;
            }
            break;
        default:
            printf("Invalid Choice. Please try again.\n");
            break;
        }
        printf("do you want to choose another option?(y/n)  ");
        scanf(" %c",&ans);
    }while(ans == 'y');
}

(I'm using functions for the library but I don't think they are causing any problem since i didn't call them yet.) edited the question to add the structure

Answer 1

You have tested an end of file condition before performing any i/o on the input file. And then, when you perform the i/o with fscanf(), you did not test the result to see if the variables were successfully read.

What is happening is that scanf() is probably failing and you do not reach the end of the loop, i.e., the EOF condition. You get stuck in there until one of your assignments (strcpy(copy[i].name,books[i].name);, copy[i].id=books[i].id; or copy[i].qty=books[i].qty;) will finally cause an overflow.

To verify this, run the code in a debugger.

Using fscanf() is very tricky, always test it thoroughly.