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

[Bill Dunlap]

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.

-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
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.