Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!quintus!ok
From: ok@quintus.UUCP (Richard A. O'Keefe)
Newsgroups: comp.unix.wizards
Subject: Re: access(2) (was: Writing to A NON-Existing File in "C")
Message-ID: <899@cresswell.quintus.UUCP>
Date: 25 Apr 88 06:54:24 GMT
References: <975@unmvax.unm.edu> <2089@munnari.oz>
Organization: Quintus Computer Systems, Mountain View, CA
Lines: 13
Summary: egg on my face

I just said that "Them's the facts" about su(1) not changing the real
uid and gid, and exhibited a wee transcript to prove it.  I should read
the manual more closely, I really should.  The 'wmi' command reports
the effective and _LOGIN_ uid&gid, not the effective and _real_ uid&gid.

There are three things:
    -	the effective uid and gid (geteuid(), getegid())
    -	the real uid and gid (getuid(), getgid())
    -	who you logged in as (getlogin(), followed by getpwnam())
and all of them are discoverable.  su changes the first two but not the
third.

If I learn from my mistakes, pretty soon I'll know everything.