Background

system() and system2() calls do not work in some environments, e.g. webR (R WebAssembly; https://webr.sh). Base R uses such calls in several places. Are they all truly needed?

A good project would be to go through the R source code and see there are some that can be replaced by plain R code. From a [quick search](https://github.com/search?q=repo%3Ar-devel%2Fr-svn%20language%3Ar%20path%3A%2Fsrc%2F**%2F*.R%20%22system(%22%20OR%20%22system2(%22%20&type=code), one candidate is:

parallel::detectCores() on Linux which effectively does:

cmd <- 'grep "^processor" /proc/cpuinfo 2>/dev/null | wc -l'
value <- system(cmd, intern = TRUE)

That can easily be replaced by:

value <- if (utils::file_test("-f", "/proc/cpuinfo")) {
  bfr <- readLines("/proc/cpuinfo", warn = FALSE)
  sum(grepl("^processor", bfr))
} else {
  0L
}

This would also remove the dependency on grep and wc, and the execution of those. Those tools on the file system (e.g. /usr/bin/grep, /usr/bin/wc).

Maybe there are others?