[Haskell-cafe] Fwd: Default stdout buffering of child processofcreateProcess

Brandon Allbery allbery.b at gmail.com
Mon Aug 4 04:53:53 UTC 2014

On Mon, Aug 4, 2014 at 12:25 AM, Donn Cave <donn at avvanta.com> wrote:

> To address J.K.'s (lest I misspell) probably ironic question seriously,
> why I certainly say Haskell should strive to be as compatible as possible
> with ANSI C, whatever Mr. Allbery may think.  Gratuitous difference in
> functionality that's clearly based on C I/O would benefit no one.

I *don't* fully agree with this, just because ANSI C is partly in the
business of ensuring that ancient programs still behave to some extent, and
ancient programs often use buffered I/O in situations where it isn't ideal
but was typically better than unbuffered on ancient PDP11s, or vice versa.
:) (And often don't use line buffering, as --- if the program is old enough
--- it may predate it.)

That said, on many platforms pipes kinda give you a taste of that
environment; as IPC goes, they're fairly slow, so buffered I/O is often a
visibly faster option. (Which is why there are lighter but more complex or
less documented / characterized IPC mechanisms around on various Unix-like
systems.) And I do mean "visibly"; it's still, even on modern hardware, not
*that* difficult to end up with programs where you can see visible pauses
between emitted characters if you disable buffering completely, whereas
even with line buffering the program both loses the pauses and takes less
time to run.

But in any case, my main grump here is that anything that makes it harder
(or non-viably slower) to interface Haskell with other programs makes it
harder to use Haskell in practice. Stringing together programs with pipes
is still common in the unix world (despite the efforts of e.g. the Gnome
devs...) and Haskell defaulting to unbuffered (or line buffered, in the
case of short lines) I/O on pipes would be unfortunate.

brandon s allbery kf8nh                               sine nomine associates
allbery.b at gmail.com                                  ballbery at sinenomine.net
unix, openafs, kerberos, infrastructure, xmonad        http://sinenomine.net
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