File input/output is part of Short Circuit's Console Program Basics selection.
Task

Create a file called   "output.txt",   and place in it the contents of the file   "input.txt",   via an intermediate variable.

In other words, your program will demonstrate:

   how to read from a file into a variable
   how to write a variable's contents into a file


Oneliners that skip the intermediate variable are of secondary interest — operating systems have copy commands for that.




fun copyFile (from, to) =
let
  val instream = TextIO.openIn from
  val outstream = TextIO.openOut to
  val () = TextIO.output (outstream, TextIO.inputAll instream)
  val () = TextIO.closeIn instream
  val () = TextIO.closeOut outstream
in
  true
end handle _ => false;