[R] Is it possible to detect whether running as Rscript?

[Duncan Murdoch]

Peter Meilstrup wrote:
> I would like to write a block of code that runs when a script is being  
> run from Rscript, but not to run if the same file is being source()d,  
> or submitted via ESS, etc. As a gloss I would like to write a file  
> that looks somewhat like:
>
> #!/usr/bin/env Rscript
>
> my.func <- function(...) {
> 	#do something...
> }
>
> if ( #is.running.Rscript# ) {
> 	do.call(my.func, commandArgs(trailingOnly=TRUE))
> }
>
> If it helps, I'm thinking of something similar to the Python idiom of  
> writing
>
> #!/usr/bin/env python
>
> #class, function definitions
>
> if (__name__=='__main__'):
> 	#code to be executed when running this file directly
>
> The intent is to use R's debugging facilities to help solve a problem  
> that occurs when a script is invoked (from a makefile) with particular  
> arguments. So if the makefile invokes "my.script datafile" then I can  
> track down the problem by sourcing the script into R and trying  
> my.func("datafile")
>
> Is this doable, or is there a better alternative?
I don't know if it gives enough detail, but you could look at the 
interactive() and/or commandArgs().

Duncan Murdoch