[Rd] tempdir() may be deleted during long-running R session

[Martin Maechler]

>>>>> Dirk Eddelbuettel <edd at debian.org>
>>>>>     on Wed, 26 Apr 2017 08:40:38 -0500 writes:

    > On 26 April 2017 at 08:29, Duncan Murdoch wrote:
    > | This seems like the wrong approach.  The problem occurs as soon as the 
    > | tempdir() gets cleaned up:  there could be information in temp files 
    > | that gets lost at that point.  So the solution should be to prevent the 
    > | cleanup, not to continue on after it has occurred (as "check = TRUE" 
    > | does).  This follows the principle that it's better for the process to 
    > | always die than to sometimes silently produce incorrect results.

    > That is generally true, but also "hard" as we don't have a handle on the OS
.

Indeed...
and that was the reason I've proposed the simple platform
agnostic tool which does not entirely solve the problem (in this sense I
agree with "wrong approach") but allows to mitigate it and (by
followup changes) to work around many use case problems.

    > | Frederick posted the way to do this in systems using systemd.  We should

    > While that was a very helpful post yet it may only apply to Arch Linux as
    > stated.  My Ubuntu systems at home and work all run systemd too, but do _not_
    > automatically remove tempfiles. 

    > Yet what he suggested is quite right: we should define a proper config file
    > for this facility and then possibly also use the /run directory as many other
    > services now and (of course) also either TEMPDIR or later the code to have
    > /run be another fallback if TMP, TEMP, TMPDIR, ... are unset.

    > Distribution maintainers such as yours truly could then include this
    > configuration.

    > | be putting that in place, or the equivalent on systems using other 
    > | tempfile cleanups.  This looks to me like something that "make install" 
    > | should do, or perhaps it should be done by people putting together 
    > | packages for specific systems.

    > Doesn't 'make install' only write to $RHOME/ and below, plus $PREFIX/bin ?

Also, 'make install' is optional for good reasons.
E.g., I never ever run 'make install': I typically always have many R
versions, all available in the shell and ESS (Emacs Speaks
Statistics) via symbolic links into a directory on PATH.

Dirk mentioned (as well) that this is all very platform specific
which I do think is important. From my typical OS point of view:
  Why should the user who runs R not have the right to delete the
  tempdir which was created by the process that she runs and hence owns ?

I agree it would be an improvement if we made such deletion much
harder than it is now, and yes, there may be great (almost)
cross-platform tools available to manage this much better than
we do now, e.g., via open files.

Before we are there, I would find it useful to have a new
'tempdir' (i.e. folder/directory for R's temporary files) to be
re-created manually or automagically in those cases it has
disappeared, and that is within easy reach via the proposed
tempdir() functionality.

OTOH, I typically live very well by quickly killing
and restarting R (from inside ESS).  

The OP issue was to help newbies and computer-non-experts, the
latter nowadays comprising more than 90% of R users (I'd guess ~
98% looking at our otherwise smart students).

These are typically "slightly" confused when they ask for help and
get a pretty severe error message:

  > ?lm
  Error in file(out, "wt") : cannot open the connection
  In addition: Warning message:
  In file(out, "wt") :
    cannot open file '/tmp/RtmpztK6f7/Rtxt36972b91938': No such file or directory


Martin