Which function in which file processes registration?

We would like to add a function to the name variable when the user registers. Does anyone know where this is?

Check out these files:

  1. in “core/fn.users.php” check out this hook (around line 338 ):

fn_set_hook('fill_user_fields', $exclude);

This is the hook right before the user field is populated.

There’s a hook when users are updated (around line 1088 ):

fn_set_hook('update_profile', $action, $user_data, $current_user_data);