Thread: Modifying multiple link lists (from main) in a function

Is it possible to modify a link list created in the main function in another function without using a return. I'm asking because in my assignment I want to modify 3 link lists in the function and as far as I know it's only possible to return one modified link list. I figured out how to modify a simple int variable that way and a char array, but can't seem to figure out the proper syntax for the link lists.

For the int variable:

Code:

#include <stdio.h>

void changeVar(int *x);

int main(void){

   int x=0;
   
   changeVar(&x);
   
   printf("x = %d\n\n", x);

   system("PAUSE");
   return 0;
}

void changeVar(int *x){
      
   *x=2;
}

For the array:

Code:

void changeArray(char *arr);

int main(void){

   char array[10];
   
   array[0]='d';
   changeArray(array);
   
   printf("array[0] = %c\n\n", array[0]);

   system("PAUSE");
   return 0;
}

void changeArray(char *arr){
      
   arr[0]='a';
}

Here is what I have for the link list (I've tried different *, **, and & configs) :

Code:

// Link List Struct
typedef struct KnightsMartRestockProduct {
   int itemNum;
   struct KnightsMartRestockProduct *next;
} KMRestockProduct;

// Function Header
void customer(KMRestockProduct *restockList);


int main(void){

   KMRestockProduct* KMRestockList=(KMRestockProduct *)malloc(sizeof(KMRestockProduct));

      
   customer(KMRestockList);      // Call to function
   
   printf("itemNum = %d\n\n", KMRestockList->itemNum);

   system("PAUSE");
   return 0;
}

void customer(KMRestockProduct *restockList){
   
   KMRestockProduct* help_ptr=restockList;
   KMRestockProduct* pNewRestock=(KMRestockProduct *)malloc(sizeof(KMRestockProduct));
   
   pNewRestock->itemNum = 2;
   pNewRestock->next = NULL;
   
   if(restockList==NULL){
      pNewRestock->next=restockList;
      restockList=pNewRestock;
   }
   
   while(help_ptr->next != NULL && help_ptr->next->itemNum < pNewRestock->itemNum)
         help_ptr=help_ptr->next;
   
   pNewRestock->next=help_ptr->next;
   help_ptr->next=pNewRestock;
}

I'm just trying to modify the itemNum field of the link list from inside the function without having to use return.

Hmmmm...sorry about the lack of white space in the customer function