From: Francis Cianfrocca
>
> > On 4/22/07, Bill Kelly <billk cts.com> wrote:
> >
> > I don't understand why it would require any
changes to EM's
> > core to treat the pipe returned by popen as 'just
another
> > eventable file descriptor'? Looking at em.cpp, we
already
> > have the beginnings of event support on
nonblocking file
> > descriptors with _OpenFileForWriting. Why
couldn't the pipe
> > returned by popen be wrapped in a
FileStreamDescriptor in
> > the same manner?
> >
> > Rather than requiring changes to EM's core, it
seems like it
> > would fit in quite naturally. Am I missing
something?
>
> You're probably right. I'm going to try to get to this
today.
> To add a bit to the point about signals: EM should
completely
> hide them (and the parallel mechanism on Windows) from
user code.
> I think with Twisted you get an event (which is
triggered by a
> signal under the covers) that tells you the fork child
has ended,
> which is all you really care about, of course.
Hi Francis,
Any progress on the eventable popen?
I'm thinking of trying to add this to EM, myself, so I was
wondering if you may have already made a start on it?
And/or, any thoughts on what the API might look like? One
of the things I like about popen() in Ruby and Perl, is
that
you can get the PID of the child process.
Looking at Ruby's popen() implementation in io.c, I see
that
they're not using the popen() library call at all; but
instead
are using a custom implementation using fork/exec in order
to obtain the PID (I presume.)
Let's say we added something to the EM 'C' API, like:
const char *evma_popen (const char *command, const char
*mode);
This would return a binding, and EM would fire the usual
EM_CONNECTION_COMPLETED, _READ, _UNBOUND events. (Assuming
mode "r" for CONNECTION_READ... If mode were
"w", then presumably
one could use evma_send_data_to_connection() to write to the
pipe.
As far as signals like EPIPE, I figure they should just be
converted to CONNECTION_UNBOUND...?)
And then, in terms of the API, how to ask for the PID? I
guess,
in keeping with API calls we already have, like
evma_get_peername()
we could add one like:
int evma_get_pid (const char *binding);
...something like that?
Does this seem reasonable?
I'd really like to have an eventable popen(), and I may give
this a shot when I have time. (BTW, I don't know how to
make
it work on Windows, since their pipes don't work with
select.)
Regards,
Bill
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