Parsing command line arguments in R scripts

Question

Is there any convenient way to automatically parse command line arguments passed to R scripts?

Something like perl's Getopt::Long?

Answer 1

There are three packages on CRAN:

• getopt: C-like getopt behavior
• optparse: a command line parser inspired by Python's optparse library
• argparse: a command line optional and positional argument parser (inspired by Python's argparse library). This package requires that a Python interpreter be installed with the argparse and json (or simplejson) modules.

Update:

• docopt: lets you define a command line interface by just giving it a description in the specific format. It is a port a docopt.py.
• argparser: cross-platform command-line argument parser written purely in R with no external dependencies. This package is useful with the Rscript front-end and facilitates turning an R script into an executable script.
• minimist: A binding to the minimist JavaScript library. This module implements the guts of optimist's argument parser without all the fanciful decoration (no external dependencies)
• optigrab: parse options from the command-line using a simple, clean syntax. It requires little or no specification and supports short and long options, GNU-, Java- or Microsoft- style syntaxes, verb commands and more.

Answer 2

The simplest way is to use commandArgs(). Example - save the code below as "options.R":

options <- commandArgs(trailingOnly = TRUE)
options

Run using "Rscript options.R x y z". Result:

[1] "x" "y" "z"

i.e. a list of 3 elements, one per argument.

Answer 3

Just to complement the Rscript answer:

edd@max:~$ r -e 'print(argv)' flim flam flom
[1] "flim" "flam" "flom"
edd@max:~$ 

We just use argv in littler. I had good luck with getopt, the older of the two available parsing packages.