Provide primitives for manipulating processes and threads in the underlying OS IO.

signature OS_PROCESS =
sig
  type status
  val atExit : (unit -> unit) -> unit
  val exit : status -> ’a
  val failure : status
  val getEnv : string -> string option
  val isSuccess : status -> bool
  val sleep : Time.time -> unit
  val success : status
  val system : string -> status
  val terminate : status -> ’a
end