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From: rjd@tiger.UUCP
Newsgroups: comp.unix.wizards
Subject: Re: Built-in login command (/bin/lo
Message-ID: <142700007@tiger.UUCP>
Date: Tue, 23-Jun-87 10:11:00 EDT
Article-I.D.: tiger.142700007
Posted: Tue Jun 23 10:11:00 1987
Date-Received: Fri, 26-Jun-87 06:31:24 EDT
References: <91@decvax.UUCP>
Lines: 26
Nf-ID: #R:decvax.UUCP:-9100:tiger.UUCP:142700007:000:1021
Nf-From: tiger.UUCP!rjd    Jun 23 09:11:00 1987


> >> 	Then (I don't know if it is true anymore) mail used
> >> 	to use the /etc/utmp entry (given by: who am i)
> >> 	instead of by uid (given by: whoami).
> >
> >   Interesting, AT&T Sys V, release 2.0 and 3.0 's mail command uses your
> >LOGNAME variable as a first choice as your ID when sending mail.  (Probably
> >and unimportant bug...)
> >
> >rjd
> 
> Actually the LOGNAME bug was fairly serious.  LOGNAME is a shell 
> variable which can normally be changed by a user.  A user could chang
> their LOGNAME variable and then send mail as someone else.  On Sys V
> if you look at /etc/profile you will notice that in many cases
> after LOGNAME is set it is made into a readonly variable.  There are ways
> around this too, but enough said.
> 
> yoseff

   Even more interesting, as the Unix Sys V /etc/profile on my system did not
come with LOGNAME set to readonly (and I had not thought of it until you
mentioned it).  The only mention of LOGNAME in my /etc/profile is to merely
export it (this will change!).

rjd