Thread: Problems with Lists

So I'm reading a file line by line and storing it backwards into a list. So if the file has has this format...
1
2
3
4
The code should store each line in a list as such...
4, 3, 2 ,1

Instead the code will store the last variable in all nodes. So the final list will look like this...
4, 4, 4, 4

Here is my code...

Code:

struct node *head = NULL;

int i;

while(read(in, &i, sizeof(int)) != 0) {
    struct node *temp = malloc(sizeof(*temp));
    temp->line = &i;
    temp->next = head;
    head = temp;
}

Anybody have any ideas?

Originally Posted by oogabooga

You're not reading the file "line by line" but "binary integer by binary integer".
If you actually want to read it line by line you need to do it differently.
Is it an ascii file that you can view with "cat" (on unix) or "notepad" (on windows)?

As for what's occurring in the posted snippet:
* Using the ampersand when saving i saves it's address, not it's value.
* Since the address of i is unchanging, you save the same address in every list node.
* Since the last value that i contains is 4, you end up printing all 4's.

How to fix it depends on what you're actually doing which we can only know after you answer the questions above.

No it is not an ascii file. If you run "cat" on this file you will just get a bunch of random characters.

I added a "printf" that prints what is being put into the list durring each loop. This is the output I get.

loop one:
1

loop two:
2 2

loop three:
3 3 3

loop four:
4 4 4 4

Thanks for you help oogabooga. You were right about the "&" I should have known better. It is working fine now. Thanks again.