CODEWITHSUNDEEP
r
Spacedman
Spacedman

Reputation: 94267

Can I tell if an R script is running under littler?

Python has this handy construct:

def do_stuff():
  whatever
if __name__ == "__main__":
  do_stuff(()

so that if the file is run from the command line with python foo.py or ./foo.py and the appropriate shebang line, then the __name__ variable is set to __main__ and the file runs as a script. However you can also do from foo import do_stuff from an interactive shell or other python code and run do_stuff from there. The same script file is then acting as a module instead of as a script.

Can I do something similar in littler scripts? Something like foo.R being:

#!/bin/env r
do_stuff = function(){
  whatever
}
if(?run as r command_line?){
 do_stuff()
}

Then I can source("foo.R") and that would define do_stuff (in my default global environment, but we'll gloss over that for a bit).

One possible key is the presence of _ in the environment when running under littler (set to the script name) but something a little stronger might be nice.

Upvotes: 4

Views: 117

Answers (1)

hrbrmstr
hrbrmstr

Reputation: 78832

Something like this should work: 

#!/usr/local/bin/r --vanilla

doStuff <- function(print_me) {
  print(print_me)
}

if (!interactive()) {
  if (exists("argv")) {
    if (!is.null(argv) && length(argv)>0) {
      doStuff(argv[1])
    }
  }
}

Upvotes: 3

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