R as a Shell

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R Package is created: see https://github.com/kos59125/RaaS

example.R

> source("shell.R")
> as.command(ls)
> # Just you type "ls" as a command
> ls
Applications	Documents	Library ...
> # Arguments are passed with brackets
> ls["-l", "Documents"]
total 1456
drwxr-xr-x   6 user  user  204  1 17 20:26 Digital Editions
...
> # Original ls function also goes
> ls()
[1] "[.command"      "as.command"     "print.command"  "print.dev.null"

shell.R

print.command <- system
print.dev.null <- function(...) {}

`[.command` <- function(cmd, ...) {
   args <- sapply(list(...), shQuote)
   cmd <- paste(c(cmd, args), collapse=" ")
   result <- system(cmd)
   class(result) <- "dev.null"
   result
}

as.command <- function(cmd) {
   e <- as.environment(-1)
   cmd <- deparse(substitute(cmd))
   class(cmd) <- "command"
   assign(cmd, cmd, envir=e)
}