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

[Martin Maechler]

>>>>> 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.



    > 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
    >> > ______________________________________________
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    >> > https://stat.ethz.ch/mailman/listinfo/r-devel

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