Creating a group and becoming a member without logout/login

Yesterday, I started playing with an USB-to-serial adapter. As it turned
out, my user was not allowed to access /dev/ttyUSB0, because the user
was not part of the uucp group. Adding a user to a group is easy on
Arch/Manjaro:

    $ gpasswd -a [user] [group]
    or in my case:
    $ gpasswd -a jans uucp

But to become a member of the group without having to logout and login a
neat utility exists. Say hello to newgrp.

    $ groups
    sys network power docker lp wheel jans
    $ newgrp uucp
    $ groups
    uucp sys network power docker lp wheel jans

Never heard of this tool, but changing group memberships is not what I
tend to do once my system is configured. See man newgrp(1) for details.