tempdir() does not respect TMPDIR

Sorry, I should retract my claim that it's too late to set TMPDIR in
.Renviron.  It does indeed work on Linux and R 4.0.2, e.g.

$ cd
$ mkdir test
$ cd test
$ echo "TMPDIR=$PWD" > ./.Renviron
$ cat ./.Renviron
TMPDIR=/home/hb/test
Rscript --no-init-file -e "tempdir()"
[1] "/home/hb/test/RtmpyH47tc"

Hmm... either this has changed "recently" or I've got it wrong all the
time.  Eitherway, I need to revise the vignette in my 'startup'
package.

Sorry for the misleading comment.

So, back to your comment about it does *not* work, that is,
~/.Renviron is not read, when you double-click on an .RData file.  I
just tried with R 4.0.2 in a Windows 10 VM and I think I can reproduce
what you're describing.

The problem seems to be that when one launches Rgui via
double-clicking .RData, the Rgui will only read ./.Renviron, that is,
the .Renviron file that is located in the same folder as the .RData
file.  It will never load ~/.Renviron (e.g.
C:/Users\alice/Documents/.Renviron) unless the .RData file is in that
folder too.

This looks odd to me but it could be that I made another mistake in my
conclusions above.  I let someone else with a less mushy brain take
over from here.

/Henrik

On Sat, Aug 29, 2020 at 4:31 PM Jinsong Zhao <jszhao at yeah.net> wrote:

I read the help page, I don't understand it very well, since I set the
environmental variable TMPDIR in .Renviron. What confused me is when
double clicking the *.RData to launch R, the tempdir() does not respect
the environmental variable TMPDIR, but launch R by double clicking Rgui
icon does.

Best,
Jinsong

On 2020/8/30 0:36, Henrik Bengtsson wrote:

It is too late to set TMPDIR in .Renviron.  It is one of the
environment variables that has to be set prior to launching R.  From
help("tempfile", package = "base"):

The environment variables TMPDIR, TMP and TEMP are checked in turn and
the first found which points to a writable directory is used: if none
succeeds ?/tmp? is used. The path should not contain spaces. **Note
that setting any of these environment variables in the R session has
no effect on tempdir(): the per-session temporary directory is created
before the interpreter is started.**

/Henrik

On Sat, Aug 29, 2020 at 6:40 AM Jinsong Zhao <jszhao at yeah.net> wrote:

Hi there,

When I started R by double clicking on Rgui icon (I am on Windows), the
tempdir() returned the tmpdir in the directory I set in .Renviron. If I
started R by double clicking on a *.RData file, the tempdir() return the
tmpdir in the directory setting by Windows system. I don't know whether
it's designed.

   > sessionInfo()

R version 4.0.2 (2020-06-22)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 10 x64 (build 18363)
...

Best,
Jinsong