Search fuction

Sorry new to word press coding / php

I have a website which has a search function in the header which searches the whole site however I want to add a search function in a category page which only searches in that category.

Can i use the current search function but say if in category (directory) only show results for that category?

This is what calls the current search function <?php get_search_form() ;?>
could I add something in here or do I need to write a whole new search function.

Help much appreciated…