If I add myself to a group, it applies only to newly launched processes. Actually it's more restricted than that; it seems to apply only to new logins. I'm not sure what the exact mechanism is, but that's not my question (though I'm curious about that too).
My question is this: Is it possible to update my group membership in the current shell process?
I suspect the answer is no.
An example (this is not a direct copy-and-paste):
$ groups ; groups kst kst oldgroup1 oldgroup2 kst : kst oldgroup1 oldgroup2 $ sudo adduser kst newgroup [sudo] password for kst: Adding user `kst' to group `newgroup' ... Adding user kst to group newgroup Done. $ groups ; groups kst kst oldgroup1 oldgroup2 kst : kst oldgroup1 oldgroup2 newgroup $
adduser, my account is a member of
newgroup, but that membership is not reflected in the current shell process.
The obvious solution is to log out and log in again, but that's inconvenient.