Printing Structs inside Structs

Question

I want to print a structure of structures. My code currently looks like this: (I haven't pasted it here, but Shelf is just a typedef of struct shelf).

struct shelf {
    struct book *books;
    struct shelf *next;
};

struct book {
    int text;
    int image;
    struct book *next;
};

Shelf create_shelf(void) {
    Shelf new_shelf = malloc(sizeof (struct shelf));
    new_shelf->next = NULL;
    new_shelf->books = NULL;
    return new_shelf;
}

I now want to print my shelves, the books inside them and each image and text in each of these books like this:

Output: , , ... and so on, where text1 and image1 refers to book1.

I've started to try to code this, but I cannot understand what is wrong with my print function below. How would I approach printing everything while only allowing the input "Shelf shelf" as the argument in my function?

void print_everything (Shelf shelf) {
    while (shelf != NULL) {
        printf("%d, %d", shelf->books->text, shelf->books->image);
    }
}

Thanks!

Make your `print_everything` follow the `next` pointers until it reaches the end of the list. Right now it's an infinite loop when you pass it a non-null argument. — Gereon, Apr 17 '21 at 13:09
Are you sure the text and image are supposed to be just numbers? — Emanuel P, Apr 17 '21 at 15:51

Linux Geek · Answer 1 · 2021-04-17T13:40:10.977

1

Considering Shelf is typedef of struct shelf * and not struct shelf.

  void print_everything (Shelf shelf) {
        while (shelf != NULL) {
            printf("%d, %d", shelf->books->text, shelf->books->image);
            shelf = shelf -> next; // Add this line
        }
    }

edited Apr 17 '21 at 13:40

answered Apr 17 '21 at 13:33

Linux Geek

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[Don't cast the return value of `malloc`](https://stackoverflow.com/questions/605845/do-i-cast-the-result-of-malloc). – dbush Apr 17 '21 at 13:35
3

Oops, `sizeof(Shelf)` would just be the size of a pointer. – David Grayson Apr 17 '21 at 13:36
1

How about quotes around the format specifier string? – Paul Ogilvie Apr 17 '21 at 13:39
1

Considering _never_ to hide pointers in typedefs? – Paul Ogilvie Apr 17 '21 at 13:40
@PaulOgilviet My bad, I just copied the code and added the last line without checking the code. – Linux Geek Apr 17 '21 at 13:41
@PaulOgilvie I said that because his code wouldn't run if he didn't `typedef` it to `struct shelf *` – Linux Geek Apr 17 '21 at 13:44

Printing Structs inside Structs

1 Answers1