Command Argument Parsing.

scribe

The goal of scribe is to provide a detailed argument parser for Rscript. This package contains no dependencies outside of base and methods. The core functions utilize ReferenceClasses under the hood.

library(scribe)

Install {scribe} from CRAN with:

install.packages("scribe")

Alternatively, you can install the development version of {scribe}GitHub with:

# install.packages("devtools")
devtools::install_github("jmbarbone/scribe")

You can enter command arguments as a vector to test out the behavior. Arguments can be added to the scribeCommandArgs class (here as ca). Default behavior tries to parse objects but additional control can be taken.

ca <- command_args(c("-a", "1", "-b", "2"))
ca$add_argument("-a")
ca$add_argument("-b")
args <- ca$parse()

str(args$a + args$b)
#>  int 3

Control

# don't convert numbers
ca <- command_args(c("-a", "1", "-b", "1.0"))
ca$add_argument("-a", convert = as.character)
ca$add_argument("-b", convert = as.character)
ca$parse()
#> $a
#> [1] "1"
#> 
#> $b
#> [1] "1.0"

# convert numbers to integers
ca <- command_args(c("verbose", "1", "1.5", "1.9"))
ca$add_argument("verbose", action = "flag")
ca$add_argument("...", convert = as.integer)
ca$parse()
#> $verbose
#> [1] TRUE
#> 
#> $...
#> integer(0)

# use functions for more control
ca <- command_args(c("verbose", "12-9-2022", "12-10-2022"))
ca$add_argument("verbose", action = "flag")
ca$add_argument("...", convert = function(i) as.Date(i, "%m-%d-%Y"))
ca$parse()
#> $verbose
#> [1] TRUE
#> 
#> $...
#> Date of length 0

You’ll probably use {scribe} within small scripts that can be called from your favorite terminal. The example below uses a function to call this file, but if it is added to your PATH you’d be able to call it directly:

r-file -a 1 -b 9

lines <- "
#! /usr/bin/env -S Rscript --vanilla 

library(scribe)
ca <- scribe::command_args()
ca$add_argument('-a', default = 1)
ca$add_argument('-b', default = 2)
args <- ca$parse()

foo <- function(a, b, ...) {
  a + b
}

do.call(foo, args)
"

file <- tempfile()
writeLines(lines, file)

rscript <- function(x, args = character()) {
  args <- c("--vanilla", x, args)
  res <- system2("Rscript", args, stdout = TRUE)
  writeLines(res)
}

rscript(file)
#> [1] 3
rscript(file, "-a 0")
#> [1] 2
rscript(file, "-a 0 -b 10")
#> [1] 10

Examples

I’ve been using {scribe} for some personal scripts. Below is a short list of some examples (mostly in my jmb repo):

• pak: call {pak} from your terminal
• update-r-pkgs: update old R packages
• todos: calls mark::todos()
• fixmes: calls mark::fixmes()

Other packages

This isn’t the first package. Most contain other dependencies, some even in different languages (e.g., python).

• {argparse}
• {optparse}
• {getopt}
• {minimist} (CRAN archived)
• {optigrab}
• {docopt}