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Date:         Thu, 22 May 2014 21:40:49 +0100
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From: Joseph Wright <joseph.wright@MORNINGSTAR2.CO.UK>
Subject: Re: Reading from the system (pipe input)
To: LATEX-L@LISTSERV.UNI-HEIDELBERG.DE
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Status: R

On 22/05/2014 20:42, David Carlisle wrote:
> On 22/05/2014 17:09, Joseph Wright wrote:
>> Hello all,
>>
>> Currently, we have \ior_open:Nn for reading from a file, but no defined
>> interface for using the 'pipe' shell escape provided by pdfTeX. As we
>> forbid spaces in file names,
> 
> why do we do that? Spaces in filenames always seem like an abomination
> to me.
> But that seems to be a relic on the 1970s I've noticed that people who
> started using
> computers this century don't seem to think anything of using a
> descriptive phrase
> as a filename...

The logic here was that, at least as I understand it, there are some
places where you can't just 'wrap up spaces' and have them work. In
particular, there are some comments about dvips and included graphics
which suggest that space behaviour is hard-coded in that case and can't
be changed. (MiKTeX also does some 'interesting' things with BibTeX
input names containing spaces.) I may have this wrong: can other more
knowledgeable people comment?

This can of course be changes if required.

> Shouldn't we just allow spaces (and leading | or any other system
> dependent special
> syntax) just surrounding any user supplied name by " " to keep it together?

Space behaviour notwithstanding, I think the point here is that the pipe
input approach is sufficiently different from a 'real' file to deserve a
separate interface.
-- 
Joseph Wright