In creating a command line tool using R, I decided to use the docopt package. It works for passing flags, but I can't figure out how to pass two numeric values. See the below code:
#! /usr/bin/Rscript
'usage: ./test.R [-lr <low> -hr <high>]
options:
-h --help Shows this screen
-lr --low <low> Passes low risk investiment
-hr --high <high> Passes high risk investiment' -> doc
library(docopt)
# retrieve the command-line arguments
opts <- docopt(doc)
# what are the options? Note that stripped versions of the parameters are added to the returned list
cat(opts$high)
cat(opts$low)
str(opts)
Whenever I try to run using ./test.R -lr 2000 -hr 4000 it warns me that the methods package is being loaded and returns nothing else.
First, -h is specified twice: once for "help", another for "high", so you'll run into problems there. To fix this, I'll use upper-case letters for the short arguments. Second, the argument to an option must either be in <angular-brackets> or UPPER-CASE, so -lr doesn't work. (Apparently it also needs a space between the option and its argument.) I'll expand it to be the same named arguments as for the long options.
Additionally (though perhaps not strictly required), I think a comma helps clarify things. (Edit: apparently docopt.R doesn't like the leading ./ on usage, so I've updated the output.)
usage: test.R [-L <low> -H <high>]
options:
-h, --help Shows this screen
-L <low>, --low <low> Passes low risk investiment
-H <high>, --high <high> Passes high risk investiment
(I found the requirements for docopt at http://docopt.org/. I found that their interactive docopt demo worked quite well, too.)