Need info on fetching effective and other user ids of a process

[Engg-blogger]

Hi Team - I am trying to fetch ruid, euid and fsuid along with gid for a process, similar to https://github.com/bpftrace/bpftrace/blob/master/tools/setuids.bt
I was able to fetch the uid.
Could you point me to the documentation where I can get some information on how to write this tooling. Thanks.