Question

I know that I can use commandArgs to read the command line arguments passed to a script in R, but I would like to debug a command line script by sourceing it in R and making it run using custom command line arguments. Is there a way of modifying the command line arguments without modifying the script file?

My scripts are normally using the optparse package for actual argument parsing, if that helps.

Answer 1

How about simply overwriting it with your own definition, e.g.

commandArgs <- function(trailingOnly=FALSE) { 
    args<- c("/foo/bar", "baz") 
    # copied from base:::commandArgs
    if (trailingOnly) {
        m <- match("--args", args, 0L)
        if (m) 
            args[-seq_len(m)]
        else character()
    }
    else args
}