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

[Henrik Bengtsson]

Oh, I see, I misunderstood.  Thanks for clarifying.

One more thing, to mix-and-match environment variables and strings
with escaped characters, while mimicking how POSIX shells does it, by
using strings with double and single quotes. For example, with:

$ cat .Renviron
APPDATA='C:\Users\foobar\AppData\Roaming'
R_LIBS_USER="${APPDATA}"'\R-library'

we get:

$ Rscript --no-init-file --quiet -e 'cat(sprintf("R_LIBS_USER=[%s]\n",
Sys.getenv("R_LIBS_USER")))'
R_LIBS_USER=[C:\Users\foobar\AppData\Roaming\R-library]

and

$ source .Renviron
$ echo "R_LIBS_USER=[${R_LIBS_USER}]"
R_LIBS_USER=[C:\Users\foobar\AppData\Roaming\R-library]

/Henrik

On Sun, Oct 31, 2021 at 2:59 AM Tomas Kalibera <tomas.kalibera using gmail.com> wrote:
>
>
> On 10/31/21 2:55 AM, Henrik Bengtsson wrote:
> >> ... 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"
>
> Yes, but as I wrote "I think the Renviron files should be written in a
> way so that they would work the same in a POSIX shell". This is why
> single quotes. With double quotes, backslashes are interpreted
> differently from a POSIX shell.
>
> Tomas
>
>
> >
> > /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
> >>>       >> > ______________________________________________
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> >>>       >> > https://stat.ethz.ch/mailman/listinfo/r-devel
> >>>
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