Passing command line arguments to R CMD BATCH

Question

I have been using R CMD BATCH my_script.R from a terminal to execute an R script. I am now at the point where I would like to pass an argument to the command, but am having some issues getting it working. If I do R CMD BATCH my_script.R blabla then blabla becomes the output file, rather than being interpreted as an argument available to the R script being executed.

I have tried Rscript my_script.R blabla which seems to pass on blabla correctly as an argument, but then I don't get the my_script.Rout output file that I get with R CMD BATCH (I want the .Rout file). While I could redirect the output of a call to Rscript to a file name of my choosing, I would not be getting the R input commands included in the file in the way R CMD BATCH does in the .Rout file.

So, ideally, I'm after a way to pass arguments to an R script being executed via the R CMD BATCH method, though would be happy with an approach using Rscript if there is a way to make it produce a comparable .Rout file.

Answer 1

My impression is that R CMD BATCH is a bit of a relict. In any case, the more recent Rscript executable (available on all platforms), together with commandArgs() makes processing command line arguments pretty easy.

As an example, here is a little script -- call it "myScript.R":

## myScript.R
args <- commandArgs(trailingOnly = TRUE)
rnorm(n=as.numeric(args[1]), mean=as.numeric(args[2]))

And here is what invoking it from the command line looks like

> Rscript myScript.R 5 100
[1]  98.46435 100.04626  99.44937  98.52910 100.78853

---

Edit:

Not that I'd recommend it, but ... using a combination of source() and sink(), you could get Rscript to produce an .Rout file like that produced by R CMD BATCH. One way would be to create a little R script -- call it RscriptEcho.R -- which you call directly with Rscript. It might look like this:

## RscriptEcho.R
args <- commandArgs(TRUE)
srcFile <- args[1]
outFile <- paste0(make.names(date()), ".Rout")
args <- args[-1]

sink(outFile, split = TRUE)
source(srcFile, echo = TRUE)

To execute your actual script, you would then do:

Rscript RscriptEcho.R myScript.R 5 100
[1]  98.46435 100.04626  99.44937  98.52910 100.78853

which will execute myScript.R with the supplied arguments and sink interleaved input, output, and messages to a uniquely named .Rout.

Edit2:
You can run Rscript verbosely and place the verbose output in a file.

Rscript --verbose myScript.R 5 100 > myScript.Rout

Answer 2

After trying the options described here, I found this post from Forester in r-bloggers . I think it is a clean option to consider.

I put his code here:

From command line

$ R CMD BATCH --no-save --no-restore '--args a=1 b=c(2,5,6)' test.R test.out &

Test.R

##First read in the arguments listed at the command line
args=(commandArgs(TRUE))

##args is now a list of character vectors
## First check to see if arguments are passed.
## Then cycle through each element of the list and evaluate the expressions.
if(length(args)==0){
    print("No arguments supplied.")
    ##supply default values
    a = 1
    b = c(1,1,1)
}else{
    for(i in 1:length(args)){
      eval(parse(text=args[[i]]))
    }
}

print(a*2)
print(b*3)

In test.out

> print(a*2)
[1] 2
> print(b*3)
[1]  6 15 18

Thanks to Forester!

Answer 3

You need to put arguments before my_script.R and use - on the arguments, e.g.

R CMD BATCH -blabla my_script.R

commandArgs() will receive -blabla as a character string in this case. See the help for details:

$ R CMD BATCH --help
Usage: R CMD BATCH [options] infile [outfile]

Run R non-interactively with input from infile and place output (stdout
and stderr) to another file.  If not given, the name of the output file
is the one of the input file, with a possible '.R' extension stripped,
and '.Rout' appended.

Options:
  -h, --help        print short help message and exit
  -v, --version     print version info and exit
  --no-timing           do not report the timings
  --            end processing of options

Further arguments starting with a '-' are considered as options as long
as '--' was not encountered, and are passed on to the R process, which
by default is started with '--restore --save --no-readline'.
See also help('BATCH') inside R.