How to access structure variable defined in another structure?

Question

I have following structure

typedef struct List_Node {
     struct File_Descriptor *data;
     char *key;
    struct List_Node *next;
}List_Node;

Now I inserted some values into the both the structures and want to access the data of type File_descriptor. How to do this?

I tried this

struct List_Node *ln1;
printf("%s", ln1.File_Descriptor->data);

but it is giving error

error: request for member ‘error: File_Descriptor’ in something not a structure or union`

There is no structure inside the structure; only a pointer. (which could point to an incomplete type) — wildplasser
– wildplasser, Commented Oct 15, 2012 at 21:59

mattjgalloway · Accepted Answer · 2012-10-15 21:43:14Z

2

You just want:

struct List_Node *ln1;
printf("%s", ln1->data);

struct File_Descriptor is the type. data is the struct member name.

Also though the printf format looks entirely wrong. Not sure what you're trying to do there. %s is string, and data certainly doesn't look like a string.

answered Oct 15, 2012 at 21:43

mattjgalloway

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3 Comments

aschepler Over a year ago

It can't be a good idea to use "%s" with an argument of type struct File_Descriptor*

mattjgalloway Over a year ago

@aschepler Indeed. Added that to my answer.

hmjd Over a year ago

I made so many mistakes in my answer which you kindly corrected I just deleted it. +1.

nickolayratchev · Accepted Answer · 2012-10-15 21:45:14Z

1

I believe you are confusing the type name with the variable name. In order to access the data member of the List_Node struct, you use the following:

struct List_Node *ln1; // initialize this
printf("%s", ln1->data);

Don't forget that you first have to initialize the ln1 pointer to point to a valid memory location before dereferencing it.

answered Oct 15, 2012 at 21:45

nickolayratchev

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