Subject: Re: getenv() can't differentiate "defined but empty" and "undefined"
From: Prof Brian D Ripley (email@example.com)
Date: Thu 30 Sep 1999 - 00:52:35 EST
On Wed, 29 Sep 1999, Martin Maechler wrote:
> getenv(<varname>) currently returns ""
> if the <varname> is undefined.
> However, if <varname> is defined but empty,
> getenv(<varname>) still only returns "".
> I think this is quite unfortunate
> but consistent with the prototype.
> I'd propose to change the current behavior.
> Something which should be pretty back compatible would
> for the first case (undefined environment variable)
> to return "" with an attribute "defined" set to FALSE
> i.e. return(structure("", defined = FALSE))
> Does anyone see a problem with this approach ?
I think it should really be NULL if undefined: attributes which may or may
not be there are a nuisance. The only problem I can see is in
system.gnw.r, whihc doe use nchar on getenv.
Small point: when do you want to change this? It is platform-specific code.
-- Brian D. Ripley, firstname.lastname@example.org Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ University of Oxford, Tel: +44 1865 272861 (self) 1 South Parks Road, +44 1865 272860 (secr) Oxford OX1 3TG, UK Fax: +44 1865 272595
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