Linked list doesn't work - c

Question

I have the following code, when I add nodes why does it reset all nodes to the most recent nodes data? Assuming everything else in the codes works correctly, parsing etc. can anyone identify a problem with the list. See output at the bottom.
typedef char* string;
typedef struct linked_list listType;
typedef struct linked_list* linked_list;
typedef struct node NodeType;
typedef struct node* Node;
typedef enum boolean{
true = 1,
false = 0
}boolean;
struct node{
Node next;//next node in the list
string *transData;//listAdd--->string data[]
};
struct linked_list{
Node head;//first node in the list
int size;//size of list, number of nodes in list
};
boolean add(linked_list list, string *data)
{
boolean retval = false;//default retval is false
Node nod;//node to add
nod = (Node)malloc(sizeof(NodeType));
nod->transData = data;
nod->next = NULL;
//list size is 0
if(list->head == NULL)
{
list->head = nod;
printf("First Node added: '%s'\n", nod->transData[0]);fflush(stdout);
retval = true;
}
//nodes already in list
else
{
printf("List with nodes already\n");
fflush(stdout);
Node node = list->head;
//iterating through nodes
while(node->next != NULL)
{
node = node->next;
}//while
node->next = nod;
printf("Node added: '%s'\n", nod->transData[0]); fflush(stdout);
retval = true;
}
list->size+=1;
return retval;//success
}
/**
* Returns the size of the list.
*/
int listSize(linked_list list)
{
return list->size;
}
/**
*Can only print with 2 or more elements
*/
void printList(linked_list list)
{
int i=0;
Node nod = list->head;
int length = listSize(list);
printf("ListSize:%d\n",listSize(list));
fflush(stdout);
while(nod->next != NULL)
{
printf("Node %d's data: %s\n", i, nod->transData[0]);
fflush(stdout);
nod = nod->next;
i++;
}
}//printlist
Output:
trans 5 5
Argument 1: trans
Argument 2: 5
Argument 3: 5
Last spot(4) is: (null)
name of command: trans
ID 1
First Node added: 'trans'
ListSize:1
>>check 4
Argument 1: check
Argument 2: 4
Last spot(3) is: (null)
name of command: check
ID 2
List with nodes already
Node added: 'check'
ListSize:2
Node 0's data: check
>>trans 4 4
Argument 1: trans
Argument 2: 4
Argument 3: 4
Last spot(4) is: (null)
name of command: trans
ID 3
List with nodes already
Node added: 'trans'
ListSize:3
Node 0's data: trans
Node 1's data: trans
>>check 5
Argument 1: check
Argument 2: 5
Last spot(3) is: (null)
name of command: check
ID 4
List with nodes already
Node added: 'check'
ListSize:4
Node 0's data: check
Node 1's data: check
Node 2's data: check

Answer 1

(The OP tells me that the nodes need to have arrays of strings, so the pointer-to-a-pointer thing is actually correct).
Anyhow, it looks like your problem is that every node has a pointer to the same buffer. You just keep copying different strings into the same buffer, and then you assign the address of a pointer to that buffer to each new node.
First, I'd get rid of those typedefs. I don't know how much clarity they're really adding.
Next, you need to allocate new storage for each string. The standard library strdup() function is a handy way to do that:
// Turns out it's a fixed-size array, so we can blow off some memory
// management complexity.
#define CMDARRAYSIZE 21
struct node {
Node next;
char * transData[ CMDARRAYSIZE ];
};
// Node initialization:
int i = 0;
struct node * nod = (struct node *)malloc( sizeof( struct node ) );
// Initialize alloc'd memory to all zeroes. This sets the next pointer
// to NULL, and all the char *'s as well.
memset( nod, 0, sizeof( struct node ) );
for ( i = 0; i < CMDARRAYSIZE; ++i ) {
if ( NULL != data[ i ] ) {
nod->transData[ i ] = strdup( data[ i ] );
}
}
...but then be sure that when you free each node, you call free( nod->transData[n] ) for every non-NULL string pointer in nod->transData. C is not a labor-saving language.

Answer 2

Your issue is probably due to pointer copying. You are likely referencing the same buffer in all your nodes. Try to make a copy of your string data with strdup for example.

Answer 3

Not the main issue, but your printList won't print out the last element.
Instead of while(nod->next != NULL) use while(nod != NULL)