How to get the created Authentication Token ID using API? or How to create login with authentication token?

How to get the created Authentication Token ID using API? or How to create login with authentication token?

Hi,

I have to create login access with new Rest API version, on my older version i have generated dynamic & unlimited tickets with credentials.

But in new we have to create authentication token and this tokens are seems to be limited. So please help on this.

      1. How to get already available authentication token?
                                    or
      2. How to create login for new API access?


Thanks in Advance,
Prakash Kannan K