Apply on.exit() to any environment, useful for parent frames

on.exit.env.R

#' Apply on.exit() anywhere
#'
#' Apply the on.exit() functionality to any environment
#'
#' Very useful for creating and closing temporary connections (see examples)
#'
#' @examples
#'  local_sink <- function(file){
#'    sink(file)
#'    on.exit.env(sink(),env=parent.frame())
#' }
#'
#' f <- function(){
#'   cat("Sinking to console\n")
#'   local_sink("temp.txt")
#'   cat("Sinking to temp.txt\n")
#' }
#'
#' f()
#' cat("sink has been removed!")

on.exit.env <- function(expr=NULL,add=TRUE,after=TRUE,env=parent.frame()){
   do.call("on.exit",
           list(expr=substitute(expr),
                add = substitute(add),
                after = substitute(after)),
           envir=env)
}