[Rd] Fwd: Using existing envars in Renviron on friendly Windows

[Henrik Bengtsson]

> ... If one still needed backslashes,
> they could then be entered in single quotes, e.g. VAR='c:\users'.

I don't think it matters whether you use single or double quotes -
both will work.  Here's a proof of concept on Linux with R 4.1.1:

$ cat ./.Renviron
A=C:\users
B='C:\users'
C="C:\users"

$ Rscript -e "Sys.getenv(c('A', 'B', 'C'))"
          A           B           C
  "C:users" "C:\\users" "C:\\users"

/Henrik

On Wed, Oct 27, 2021 at 11:45 AM Tomas Kalibera
<tomas.kalibera using gmail.com> wrote:
>
>
> On 10/21/21 5:18 PM, Martin Maechler wrote:
> >>>>>> Michał Bojanowski
> >>>>>>      on Wed, 20 Oct 2021 16:31:08 +0200 writes:
> >      > Hello Tomas,
> >      > Yes, that's accurate although rather terse, which is perhaps the
> >      > reason why I did not realize it applies to my case.
> >
> >      > How about adding something in the direction of:
> >
> >      > 1. Continuing the cited paragraph with:
> >      > In particular, on Windows it may be necessary to quote references to
> >      > existing environment variables, especially those containing file paths
> >      > (which include backslashes). For example: `"${WINVAR}"`.
> >
> >      > 2. Add an example (not run):
> >
> >      > # On Windows do quote references to variables containing paths, e.g.:
> >      > # If APPDATA=C:\Users\foobar\AppData\Roaming
> >      > # to point to a library tree inside APPDATA in .Renviron use
> >      > R_LIBS_USER="${APPDATA}"/R-library
> >
> >      > Incidentally the last example is on backslashes too.
> >
> >
> >      > What do you think?
> >
> > I agree that adding an example really helps a lot in such cases,
> > in my experience, notably if it's precise enough to be used +/- directly.
>
> Yes, I agree as well. I think the Renviron files should be written in a
> way so that they would work the same in a POSIX shell, so e.g.
> VAR="${VAR0}" or VAR="${VAR0}/subdir" are the recommended ways to
> preserve backslashes in VAR0. It is better to use forward slashes in
> string literals, e.g. VAR="c:/users". If one still needed backslashes,
> they could then be entered in single quotes, e.g. VAR='c:\users'.
>
> The currently implemented parsing of Renviron files differs in a number
> of details from POSIX shells, some are documented and some are not.
> Relying only on the documented behavior that is the same as in POSIX
> shells is the best choice for future compatibility.
>
> Tomas
>
> >
> >
> >      > On Mon, Oct 18, 2021 at 5:02 PM Tomas Kalibera <tomas.kalibera using gmail.com> wrote:
> >      >>
> >      >>
> >      >> On 10/15/21 6:44 PM, Michał Bojanowski wrote:
> >      >> > Perhaps a small update to ?.Renviron would be in order to mention that...
> >      >>
> >      >> Would you have a more specific suggestion how to update the
> >      >> documentation? Please note that it already says
> >      >>
> >      >> "‘value’ is then processed in a similar way to a Unix shell: in
> >      >> particular the outermost level of (single or double) quotes is stripped,
> >      >> and backslashes are removed except inside quotes."
> >      >>
> >      >> Thanks,
> >      >> Tomas
> >      >>
> >      >> > On Fri, Oct 15, 2021 at 6:43 PM Michał Bojanowski <michal2992 using gmail.com> wrote:
> >      >> >> Indeed quoting works! Kevin suggested the same, but he didnt reply to the list.
> >      >> >> Thank you all!
> >      >> >> Michal
> >      >> >>
> >      >> >> On Fri, Oct 15, 2021 at 6:40 PM Ivan Krylov <krylov.r00t using gmail.com> wrote:
> >      >> >>> Sorry for the noise! I wasn't supposed to send my previous message.
> >      >> >>>
> >      >> >>> On Fri, 15 Oct 2021 16:44:28 +0200
> >      >> >>> Michał Bojanowski <michal2992 using gmail.com> wrote:
> >      >> >>>
> >      >> >>>> AVAR=${APPDATA}/foo/bar
> >      >> >>>>
> >      >> >>>> Which is a documented way of referring to existing environment
> >      >> >>>> variables. Now, with that in R I'm getting:
> >      >> >>>>
> >      >> >>>> Sys.getenv("APPDATA")    # That works OK
> >      >> >>>> [1] "C:\\Users\\mbojanowski\\AppData\\Roaming"
> >      >> >>>>
> >      >> >>>> so OK, but:
> >      >> >>>>
> >      >> >>>> Sys.getenv("AVAR")
> >      >> >>>> [1] "C:UsersmbojanowskiAppDataRoaming/foo/bar"
> >      >> >>> Hmm, a function called by readRenviron does seem to remove backslashes,
> >      >> >>> but not if they are encountered inside quotes:
> >      >> >>>
> >      >> >>> https://github.com/r-devel/r-svn/blob/3f8b75857fb1397f9f3ceab6c75554e1a5386adc/src/main/Renviron.c#L149
> >      >> >>>
> >      >> >>> Would AVAR="${APPDATA}"/foo/bar work?
> >      >> >>>
> >      >> >>> --
> >      >> >>> Best regards,
> >      >> >>> Ivan
> >      >> > ______________________________________________
> >      >> > R-devel using r-project.org mailing list
> >      >> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >
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