# Maybe my implementation is wrong... it's pretty much this (cleared from
# comments, `txt_stdin` is what one GUI component sets, and Button runs the proc
# each time it's clocked)
var clear_stdout = false # if clears history
var
    txt_stdin  = ""
    txt_stdout = ""

proc runValidator(sender: Button) =
    let ex = execCmdEx(txt_stdin)
    if ex[1] == 0 and ex[0] != "":
        add(txt_stdout, ex[0])
    if clear_stdout:
        discard
    echo "IN:" & txt_stdin
    echo txt_stdout