[Rd] Best way to locate R executable from within R?

[Gabor Grothendieck]

On Tue, May 22, 2012 at 1:34 PM, Henrik Bengtsson <hb at biostat.ucsf.edu> wrote:
> Hi,
>
> I'd like to spawn of a new R process from within R using system(),
> e.g. system("R -f myScript.R").  However, just specifying "R" as in
> that example is not guaranteed to work, because "R" may not be on the
> OS's search path.
>
>  What is the best way, from within a running R, to infer the command
> (basename or full path) for launching R in way that it works on any
> OS?  I came up with the following alternatives, but I'm not sure if
> they'll work everywhere or not:
>
> 1. Rbin <- commandArgs()[1];
>
> 2. Rbin <- file.path(R.home(), "bin", "R");
>
> Other suggestions that are better?
>

At least on Windows one could run R via R.exe, Rterm.exe or Rgui.exe
amd #2 would not pick up the differences.  On the other hand if I do
this on the Windows command line on my Vista system with R 2.15.0
patched:

cd \program files\R\R-2.15.x\bin\i386
Rterm.exe

and then enter commandArgs() into R, the output is "Rterm.exe" with no path.

The fact that one can have 32 bit and 64 bit R executables on the same
system complicates things too.

Thus, on Windows something like this might work:

   file.path(R.home("bin"), R.version$arch, basename(commandArgs()[[1]]))

If there are cases that I missed then this might pick up those too:

   R <- commandArgs()[[1]]
   if (R == basename(R)) R <- file.path(R.home("bin"), R.version$arch, R)

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