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

[Simon Urbanek]

On May 22, 2012, at 3:34 PM, Gabor Grothendieck wrote:

> On Tue, May 22, 2012 at 3:28 PM, Gabor Grothendieck
> <ggrothendieck at gmail.com> wrote:
>> On Tue, May 22, 2012 at 3:05 PM, Henrik Bengtsson <hb at biostat.ucsf.edu> wrote:
>>> On Tue, May 22, 2012 at 11:39 AM, Gabor Grothendieck
>>> <ggrothendieck at gmail.com> wrote:
>>>> 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.
>>> 
>>> Thanks, I overlooked this need.  For my particular use case, I'm
>>> interested in launching R in "batch" mode, so "R" will do (but not
>>> "Rgui").
>>> 
>>>> 
>>>> 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)
>>> 
>>> FYI, R.home("bin") is not the same as file.path(R.home(), "bin"), cf.
>>> help("R.home").  R.home("bin") will pick up the current architecture
>>> directory (by using .Platform$r_arch), e.g.
>>> 
>>>> R.home("bin")
>>> [1] "C:/PROGRA~1/R/R-2.15.0patched/bin/x64"
>>> 
>>> /Henrik
>>> 
>> 
>> Then perhaps something like this which is still not 100% foolproof but
>> should work most of the time:
>> 
>> Find(file.exists, c(
>>   commandArgs()[[1]],
>>   file.path(R.home("bin"), commandArgs()[[1]]),
>>   file.path(R.home("bin"), "R")
>> ))
> 
> So that the last one tried works on Windows too it should be:
> 
> Find(file.exists, c(
>   commandArgs()[[1]],
>   file.path(R.home("bin"), commandArgs()[[1]]),
>   file.path(R.home("bin"), "R"),
>   file.path(R.home("bin"), "R.exe")
> ))
> 

Obviously, you don't want to do that for reasons discussed previously.



> 
> 
>> --
>> Statistics & Software Consulting
>> GKX Group, GKX Associates Inc.
>> tel: 1-877-GKX-GROUP
>> email: ggrothendieck at gmail.com
> 
> 
> 
> -- 
> Statistics & Software Consulting
> GKX Group, GKX Associates Inc.
> tel: 1-877-GKX-GROUP
> email: ggrothendieck at gmail.com
> 
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