Is there a package to process command line options

Question

Is there a package to process command-line options in R?

I know commandArgs, but it's too basic. Its result is basically the equivalent to argc and argv in C, but I'd need something on top of that, just like boost::program_options in C++, or GetOptions::Long in perl.

In particular, I'd like to specify in advance what options are allowed and give an error message if the user specifies something else.

The call would be like this (with user options --width=32 --file=foo.txt):

R --vanilla --args --width=32 --file=foo.txt < myscript.R

or, if Rscript is used:

myscript.R --width=32 --file=foo.txt 

(Please don't say, "why don't you write it yourself, it's not that hard". In other languages you don't have to write it yourself either. :)

Answer 1

getopt for R

Answer 2

How about commandArgs with eval for a built in solution?

test.R

## 'trailingOnly=TRUE' means only parse args after '--args'
args=(commandArgs(trailingOnly=TRUE))

## Supply default arguments
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)

and to invoke it

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

The usual caveats w.r.t using eval apply of course.

Shamelessly stolen from this blog post.