Re: [patch] who and stale utmp entries

[Tim Waugh]

On Wed, Mar 23, 2005 at 12:42:10PM -0800, Paul Eggert wrote:

> That patch has a problem when process-IDs are reused.

Agreed: the false positives that would normally be eliminated by the
patch would not be in the case of the process ID having been re-used
(and still being active).

> Can you please explain more what is going on here?  As I understand
> it, "users" and "pinky" do not suffer from the stale-utmp problem.

They do.  I have a stale utmp entry on my machine for 'root' -- what
happened was that I reset the machine during a root login session.
users, pinky, and who all claim that root is still logged in.

All the patch does is claim that a utmp entry referencing a process no
longer running is stale and should not be used.

> Also, does that patch attempt to send signals even when "who" is
> invoked as (say) "who -q file"?  That doesn't sound quite right.

Well, it's kill (..., 0), so it's not really sending any signals
anywhere.

However, perhaps the extra check should be omitted if FILE is
specified.

Tim.
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