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IOCTL$ Function Details
 
Syntax
  IOCTL$([#]filenumber)
 
The filenumber is the BASIC file number used to open the device. The
IOCTL$ function is most frequently used to test whether an IOCTL
statement succeeded or failed or to obtain current status information.
 
  Note: BASIC devices ( LPT1:, COM1:, COM2:, SCRN:, CONS:) and
        DOS block devices ( A: through Z:) do not support IOCTL.
 
You could use IOCTL$ to ask a communications device to return
the current baud rate, information on the last error, logical line
width, and so on. The exact information returned would depend on the
specific device driver.
 
The IOCTL$ function works only if all three of the following
conditions are met:
 
  1. The device driver is installed.
  2. The device driver states that it processes IOCTL strings. See the
     documentation for the driver. You can also test for IOCTL support
     through DOS function &H44 by using interrupt &H21 and the CALL
     INTERRUPT routine. See the CALL INTERRUPT statement for more
     information.
  3. BASIC performs an OPEN statement on a file on that device.