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From: DEDOUREK@unb.ca
Newsgroups: comp.os.minix
Subject: Re: observations-possible bug in minix
Message-ID: <20489@nigel.udel.EDU>
Date: 29 May 90 17:19:11 GMT
Article-I.D.: nigel.20489
Sender: mmdf@udel.EDU
Lines: 40

On  Tue, 29 May 90 08:25:21 EDT  Bill Powers <@VM1.NoDak.
EDU:powers@ASDS.ENET.DEC.COM> writes:

> After doing some investigation, it seems that
> that write reads in the utmp?? records and compares the users listed
> in there to the one enterd at the command line.  Except the size of
> the field for the userid  part of the utmp structure is only 8
> characters. There was no nul terminator on the string so it bled in
> with the other records in the file (ie write tried comparing
> "userid01" with "userid01tty1tty1") something like that which made it
> fail).

This is a well known problem in Unix to which I am very sensitive.
(Count the characters in "dedourek" :-)  An 8-character logon id
is legal according to most documentation.  Only 8 characters are
allotted to the user id in many Unix structures.  The documentation,
in the "fine print," points out that 8-character id's will NOT
BE NULL TERMINATED.  It is the responsibility of an application
to move the user id to a 9-character array and add a safety null
BEFORE USING ANY OF THE STANDARD STRING OPERATIONS on the user id.

If a utility in Minix has failed to do this, that is a bug.  Minix
is, however, in good company.  A recent test of one of the beta
releases of IBM's new AIX 3.0 had "who" reporting me as "dedoure".

I hope that this reminder to the Minix community from one of us
"eight characters" is accepted in the good spirit that it is
offered, and that it will help make Minix one of the leaders in
erradicating this problem.

John DeDourek, Professor
School of Computer Science
University of New Brunswick
Fredericton, N. B. CANADA
E3B 5A3

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