Get user_id by using client_id in Twitch Tv

Twitch Tv documentation gives example of finding user_id

curl -H 'Accept: application/vnd.twitchtv.v5+json' \
-H 'Client-ID: uo6dggojyb8d6soh92zknwmi5ej1q2' \
-H 'Authorization: OAuth cfabdegwdoklmawdzdo98xt2fo512y' \
-X GET 'https://api.twitch.tv/kraken/user'

but I just want to use the client_id …
How to get the user_id with only client_id?

i really scanner the whole documentation, there is no sign of possibility or impossibility! So I kinda felt lost. :worried: