I am designing a code that uses that involves a pluggin. I need to extract the current wordpress users username to fetch him special authorities. This extraction of the username is being done in a php file of the pluggin.
This is what you are looking for:
The username will be stored in the global variable $user_identity. If you are adding capabilities (I assume this is what is meant by 'special authorities') then it would make more sense to use the $user_ID global variable.