Re: [Rd] Spurious output white line in R script (PR#8631)

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Thu 23 Feb 2006 - 16:53:19 GMT

On Thu, 23 Feb 2006, Thomas Lumley wrote:

> On Thu, 23 Feb 2006, Prof Brian Ripley wrote:
>
>> On Wed, 22 Feb 2006, François Pinard wrote:
> [...]
>>>
>>> So, I was not expecting R, running with that option activated, to
>>> "volunteer" white lines. :-)
>>
>> But Simon said `with the documentation'. Not doing what you expected is
>> not a bug. Can you please point us to documentation which says that
>> end-of-file produces no output?
>>
>> This does appear to be deliberate behaviour from
>>
>> void end_Rmainloop(void)
>> {
>> Rprintf("\n");
>> /* run the .Last function. If it gives an error, will drop back to main
>> loop. */
>> R_CleanUp(SA_DEFAULT, 0, 1);
>> }
>>
>> and I think it is necessary, as R might well have a partial line of output
>> queued up for the console. So this is probably `as quietly as possible'.
>
> (While agreeing entirely on the "bug" issue), couldn't we have fflush()
> instead of sending a newline?

Well, we might not be outputting to a file ... (I did say console), and .Last() might well produce output so we need to leave the console in a suitable state. I do think we need a \n unless we can be sure that we are currently at the left margin of the console (and I am not sure we can be unless we assume all output went through R[E]printf, and even in that case we do not currently collect the information).

Consider the script

gannet% cat foo
#!/bin/sh
R --slave --vanilla <<EOF

.Last <- function() cat("goodbye\n")
cat("Hello")
EOF which produces

gannet% foo.R
Hello
goodbye
gannet%

We do not want

gannet% foo.R
Hellogoodbye
gannet%

or at least, I do not want that.

Beyond that, there must be hundreds or more reference results of test runs against which comparisons are made, and this might well affect a lot of testing code, although perhaps we could conditionalize on --slave.

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
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 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595


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Received on Fri Feb 24 05:30:14 2006

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