Re: [PATCH] tee: Add --pipe-check to allow instantly detecting closed outputs

[Carl Edquist]

On Mon, 12 Dec 2022, Arsen Arsenović wrote:

> Hi Carl,
>
> Carl Edquist <edquist@cs.wisc.edu> writes:
>
> > [2. text/x-diff; 0001-tee-only-fstat-outputs-if-pipe_check-is-active.patch]...
> >
> > [3. text/x-diff; 
> > 0002-tee-skip-pipe-checks-if-input-is-always-ready-for-re.patch]...
>
> Thanks for writing these, and the other patches.  I've once again been 
> stripped of time, but I think we've nailed the concept down for the most 
> part.  I think we should wait for Pádraig to voice his opinion at this 
> point.  Details can be ironed out later, and pretty easily too.

Sure...  Sorry for throwing so many patches at the list  :)

I did have in mind also to send a summarized patch series in a single 
email to make reviewing everything a bit easier.  Pádraig is the 
gatekeeper here, in any case.

The main question on my mind currently is still what's the best way to do 
the platform preprocessor logic for poll vs select ... (assuming 
HAVE_INOTIFY is only in tail.c for "tail -f" mode)

And, i don't know if this would help "sell" it or not, but locally i have 
separated out the iopoll implementation to a separate iopoll.c/.h, and as 
an example successfully added a --pipe-check option to cat and tr.  (Not 
to pressure anyone to take it, but, sometimes it's easier to tell if you 
like an idea or not when you have a patch to look at...)

Personally, i see this broken-pipe detection being useful in tee, cat, 
sed, and grep for starters.  (Though i know sed and grep live outside 
coreutils.)

In some ways i feel like tee is actually the most immediate use case 
though.

cat and sed mostly came into play for me as a way to type commands into a 
socket; though as it seems to me now, "broken-pipe" detection for a socket 
may not even be possible.


All for now.

Have a good one,

Carl