R Script: Determine whether the script is run in the GUI or from command line

Question

Is it possible to determine - from within the script - whether the script is running in the R-GUI (specifically R.app on OS X) or whether it has been called from Terminal/command line (i.e. R --vanilla -f script.R)? If so, how is this possible?

I'm asking because I have a script that can run parallelized (using the doMC library), which should not be used from the GUI. Sometimes I need to further process the data calculated in the script, so I'd like to call the script from the GUI on these occasions.

Answer 1

In C, you would use the isatty function. If you could find an equivalent function in R (probably in a UNIX or file system library), that should help.

Answer 2

Perhaps you are looking for interactive()?