Int 21 Fn 46  - Dos 2+ - "dup2", "forcedup" - Force Duplicate File Handle  [D]

   AH = 46h
   BX = file handle
   CX = file handle to become duplicate of first handle

Return: CF clear if successful
   CF set on error
       AX = error code (04h,06h) (see #1366 at AH=59h/BX=0000h)

Notes: closes file with handle CX if it is still open
   DOS 3.30 hangs if BX=CX on entry
   moving file pointer for either handle will also move it for the other,
     because both will refer to the same system file table

See Also: AH=3Dh,AH=45h