Re: [Rd] Possible changes to connections

From: Prof Brian Ripley <>
Date: Fri, 01 Jun 2007 07:39:07 +0100 (BST)

On Fri, 1 Jun 2007, mel wrote:

> Prof Brian Ripley a écrit :
>>> I use getConnection().
>>> In the context in which I use it, the number of the connection is
>>> known a priori.
>> I don't see how you can know it 'a priori': it is an implementation detail
>> (and since R itself uses connections, those details could easily change).
> (disclaimer : I don't claim its the best way to proceed)
> Before launching my app, the connections context is :
> > showConnections(all=TRUE)
> description class mode text isopen can read can write
> 0 "stdin" "terminal" "r" "text" "opened" "yes" "no"
> 1 "stdout" "terminal" "w" "text" "opened" "no" "yes"
> 2 "stderr" "terminal" "w" "text" "opened" "no" "yes"
> So, the call to socketConnections() creates always (at least
> for all my experiments) a connection with number 3.
> Btw, if (socketConnections(...) != 3) the application simply
> don't launch.
> So, if the application runs, it's sure that this is with a
> connection number==3.
> That's why I say that "the number of the connection is known a priori".

You don't *know* that: it depends on how R internally numbers connections and what the startup code does. That detail will almost certainly change.

> Of course, the connection number could also be retrieved eg using
> the description field.

For now, at least.

Brian D. Ripley,        
Professor of Applied Statistics,
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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