In Ubercart Which Hook is reponsible for adding product to the cart page(On clicking add-cart-button)? In ubercart,While buyer sees a product and clicks on add-to-cart button for buying that product, i want to know which action is responsible for that product being added in to the cart? 

I want to edit the sell price, so that only this question.
Already tried this hook, but it was not printing anything,

    mymodulename_uc_add_to_cart($nid, $qty, $data) {
    print "&lt;pre&gt;";print_r($data);print "&lt;/pre&gt;";exit;

    if ($qty &gt; 1) {
        $result[] = array(
                'success' =&gt; FALSE,
                'message' =&gt; t('Sorry, you can only add one of those at a time.'),
        );
    }
    return $result;
}


Which of these hooks 

hook_uc_add_to_cart
hook_uc_add_to_cart_data
hook_uc_cart_checkout_start
hook_uc_cart_display
hook_uc_cart_item_delete
hook_uc_cart_item_insert
hook_uc_cart_item_presave
hook_uc_cart_item_update
hook_uc_cart_pane
hook_uc_cart_pane_alter
hook_uc_checkout_complete
hook_uc_checkout_pane
hook_uc_checkout_pane_alter
hook_uc_update_cart_item
uc_checkout_pane_callback

is responsible for adding quantity and price to cart in the cart page.Or is there any other hook which is doing it ?

Any ideas? Thanks in advance
If you want to alter the cart item, then you can use hook_uc_cart_alter of ubercart. 

This hook is not in documentation of ubercart 7 but its still working for Ubercart 7. 


  This is called every time the cart is rebuild (e.g. when products are
  added), so it's a good place to alter the cart item.


I have checked uc_coupon module and hook hook_uc_cart_alter is implemented into that module. So, you can try this hook.

Edit:
Code snippets to modify the price of item 

/**
 * Implements uc_cart_alter.
 */
function mymodule_uc_cart_alter(&amp;$items ) {

  foreach ($items as $index =&gt; $item) {

   //you can add condition for your bid product

    $items[$index]-&gt;price = 100;
  }
}


For reference:

http://www.ubercart.org/docs/api/hook_uc_cart_alter