18 Nov
2021
18 Nov
'21
6:02 p.m.
Well, I don't remember Ultrix or SunOS doing this when I was one of
Columbia's Unix Systems Programmers.? However, that might mean exactly
nothing more than I don't remember and that they did do it.? I don't
remember it in any daemon that I developed.? Of course, I can barely
remember any daemon I developed...
My dissatisfaction is not with the practice itself so much as what winds
up being called a standard and who says it is.? Until somebody says
different...
On 11/18/21 11:43 AM, Dave McGuire wrote:
? Tom, you're describing "proper 1970s UNIX fashion".? A SIGHUP to
reload/reconfigure a running process has been standard since the
mid/late 1980s, perhaps even earlier.
?????????? -Dave
On 11/18/21 10:50 AM, Thomas DeBellis wrote:
The statement, "Proper Unix fashion",
leaves me somewhat uncomfortable.
Since I'm ancient, my understanding of SIGHUP is to handle a hangup
detected on the controlling terminal or the death of a controlling
process.? A hangup started out meaning dropping carrier on a modem or
DTR on a hardwired line.? It came to include a broken network
terminal connection.
When I think of how to handle a SIGHUP, I usually think of
'gracefully' stopping a process (I.E., saving the user's work instead
of ditching it) and exiting.? If you don't do that, then something
else has to be used to get rid of you, perhaps a SIGTERM.? The
problem is that if somebody wants you gone and you don't go away, you
have a 9 on your hands (SIGKILL).? Now that data is gone.
If you usurp SIGHUP for such use, then things like NOHUP won't do the
expected thing.? There are certainly reasons to be NOHUP'ed.? In your
superior breaks, you might not want to disappear so somebody has a
chance to attach a debugger to you to try to figure out what happened.
I think the better thing to do would be handle a SIGUSR1/SIGUSR2 to
reparse.
Of course, "proper" is a very relative term in Unix.? Things change
and sometimes get used for no readily apparent reason, the result
being that an unspoken 'standard' happens.? It is not uncommon.? For
example, Johnny's DECnet bridge does in fact use SIGUSR1 to display
some information. However, it uses a SIGHUP to do a reparse.? So
maybe that's the best of both worlds...
I've never felt strongly enough about the matter to suggest SIGUSR2
for a reparse, but if you want to be a purist, then it probably should.
> ------------------------------------------------------------------------
>
> On 11/18/21 9:58 AM, Paul Koning wrote:
>
>
> In proper Unix fashion it could be triggered by a SIGHUP signal