[R] Error when calling (R 4.0.x on Windows) from Python

[Duncan Murdoch]

On 27/01/2021 3:40 p.m., Bill Dunlap wrote:
> I believe the problem is from svn 77925 in gnuwin/front-ends/rcmdfn.c,
> which was committed a few days after 3.6.3 was released.  Rterm used
> to put double quotes around a command line argument only if it
> contained a space, now it double quotes all arguments.  It sees shell
> constructs like "1>" and the following file name as arguments and
> double quoting them hides them from the shell, leading to this
> problem.  I think we may have to rely on the user supplying quotes as
> needed instead of blindly adding them.

Okay, now I see what you mean.

If you invoke R using R.exe, it asks cmd.exe to run Rterm.exe, so it is 
possible that redirection would be handled.

If you invoke R directly using Rterm.exe, then my description down below 
would be correct.

Duncan Murdoch


> 
> -Bill
> 
> On Wed, Jan 27, 2021 at 12:28 PM Duncan Murdoch
> <murdoch.duncan using gmail.com> wrote:
>>
>> On 27/01/2021 3:17 p.m., Duncan Murdoch wrote:
>>> On 27/01/2021 3:38 a.m., Martin Maechler wrote:
>>>>>>>>> Martin Maechler
>>>>>>>>>        on Tue, 26 Jan 2021 12:37:58 +0100 writes:
>>>>
>>>>>>>>> Marcel Baumgartner
>>>>>>>>>        on Tue, 26 Jan 2021 08:55:48 +0100 writes:
>>>>
>>>>        >> Dear all, my colleague posted our issue on stackoverflow:
>>>>
>>>>        >> Calling R script from Python does not save log file in
>>>>        >> version 4 - Stack Overflow
>>>>        >> [https://stackoverflow.com/questions/65887485/calling-r-script-from-python-does-not-save-log-file-in-version-4]
>>>>
>>>>        >> It is about this kind of call to R:
>>>>
>>>>        >> R.exe -f code.R --args "~/file.txt" 1> "~/log.txt" 2>&1".
>>>>
>>>>        >> The issue is that the log.txt file is not created when
>>>>        >> running R 4.x.x. The same code works perfectly fine with
>>>>        >> R 3.6.x.
>>>>
>>>>        >> Any idea what's going wrong as of version 4? Regards
>>>>        >> Marcel
>>>>
>>>>        > Dear Marcel, I think the solution is embarrassingly
>>>>        > simple:
>>>>
>>>>        >> From the SO post, where she showed a bit more detail than you
>>>>        > show here, it's clear you have confused 'R.exe' and
>>>>        > 'Rscript.exe' and what you say above is not true:
>>>>
>>>>        > 'R.exe' was used for R 3.6.0 but for R 4.0.3, you/she used
>>>>        > 'Rscript.exe' instead.
>>>>
>>>>
>>>>        > ... as you've noticed now, they do behave differently,
>>>>        > indeed!
>>>>
>>>> Well, this was not the solution to their -- Windows-only -- problem.
>>>> The problem *is* indeed visible if they only use  R.exe  (also
>>>> for R 4.0.3).
>>>>
>>>> I've commented more on the SO issue (see above),
>>>> notably asking for a *minimal* repr.ex. (reproducible example),
>>>> and one *not* using "<YOUR PATH>" and setwd() ..
>>>>
>>>
>>> Isn't this purely a Python or user problem?  R shouldn't process
>>> redirection directives like
>>>
>>>      1> "~/log.txt" 2>&1
>>>
>>> because it's the shell's job to process those. If Python is acting as
>>> the shell, it needs to handle those things.  If R was handling the
>>> command via
>>
>> Oops, sent before finishing:
>>
>> If R was handling the command via system() or system2(), it would handle
>> redirection itself. If it was using the Windows-only shell(), it would
>> call cmd.exe (by default) to handle redirection.  (This is a difference
>> between R on Windows and R in Unix:  in Unix a shell is always used.)
>>
>> Duncan Murdoch
>>
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