Best way to locate R executable from within R?

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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