linked list delete function - c

Question

The following code snippet is not working right.
void deleteNode(list **start, int pos) {
int currentPosition=0;
list *currentNode;
list *nodToDelete;
currentNode = *start;
if (currentNode == NULL) {
printf("Empty List\n");
} else if (pos == 0 ) {
nodToDelete = *start;
*start = nodToDelete->next;
free(nodToDelete);
} else {
while (currentNode->next != NULL) {
if (currentPosition >= pos -1) {
break;
}
currentPosition++;
currentNode = currentNode->next;
}
if (currentPosition < pos -1 || currentNode->next == NULL) {
printf("No node at given position exists\n");
} else {
nodToDelete = currentNode->next;
currentNode = nodToDelete->next;
free(nodToDelete);
nodToDelete = NULL;
}
}
}
void displayList(list *node) {
if (node == NULL) {
printf("Empty List");
}
while (node != NULL) {
printf("%d\t", node->data);
node = node->next;
}
printf("\n");
}
int main()
{
list *start, *node;
start = NULL;
insertNode(&start, 2);
insertNode(&start, 3);
insertNode(&start, 4);
insertNode(&start, 1);
insertNode(&start, 5);
deleteNode(&start, 3);
displayList(start);
}
When executed the output is
Before Deletion 2 3 4 1 5
After Deletion 2 3 4 0 5
It is supposed to delete 1 but it is inserting 0 at its place.

Answer 1

Here is something that might work --
Replace
currentNode = nodToDelete->next;
with
currentNode->next = nodToDelete->next;
You basically need the node before the nodetodelete to have its next to point to the node that nodetodelete used to point to

Answer 2

Once you've found the node you want to take out of the list, you need to actually take it out. =)
...
nodToDelete = currentNode->next;
currentNode->next = nodToDelete->next;
free(nodToDelete);
...

Answer 3

Besides the problem with currentNode->next = nodToDelete->next; and negative positions you are mixing your ui and your logic. As much as possible you should separate the two.
Sending something to the ui is a way of reporting progress; whether the ui is a command line, a browser or a speaker. Within deleteNode, an empty list or a position that is out of bounds, is not progress. Sequentially both are the same as success - you are done. If you want failure to be to be reported, that should be done where it can lead to a separate sequence...i.e the caller. Also, by mixing in ui, you introduce an unnecessary dependency and failure (what if there's a bug in printf, YOUR function will crash when it doesn't doesn't have to). If you're function returns a defined result, the caller can decide if/how to report that result, including success (your function currently doesn't do so, and the caller has no way telling the difference between sucess or failure).