IOCTL Statement


 Example

 The following example shows how to communicate with a device driver using a
 hypothetical device driver named ENGINE. The  IOCTL statement sets the data
 mode in the driver and the  IOCTL$ function tests the data mode.

 OPEN "\DEV\ENGINE" FOR OUTPUT AS #1


 IOCTL #1, "RAW"' Tells the device that the data is raw.





 ' If the character driver "ENGINE" responds "false" from the raw data


 ' mode in the IOCTL statement, then the file is closed.


 IF IOCTL$(1) = "0" THEN CLOSE 1


 IOCTL Statement
 ----------------------------------------------------------------------------


 Action

 Transmits a control data string to a device driver.


 Syntax



  IOCTL #  filenumber%,  string$

 Remarks


 The  IOCTL statement uses the following arguments.

-----------------------------------------------------------------------------
 Argument          Description
 ----------------------------------------------------------------------------
  filenumber%      The BASIC file number used to open the device.
  string$          The command sent to the device.




 Commands are specific to the device driver. See the documentation for the
 device driver for a description of the valid  IOCTL commands. An  IOCTL
 control data string can be up to 32,767 bytes long.

 The  IOCTL statement works only if all of the following conditions are met.

   -         The device driver is installed.

   -         The device driver states that it processes  IOCTL strings. See
             the documentation for the driver.  You also can test for  IOCTL
             support through DOS function &H44 by using interrupt &H21 and
             the  INTERRUPT routine. For more information about interrupt
             &H21, function &H44, see see the  Microsoft MS-DOS  Programmer's
              Reference, or books such as  Advanced MS-DOS or  The Peter
             Norton Guide to the IBM PC.

   -         BASIC performed an  OPEN operation on a file on that device, and
             the file is still open.





 Most standard DOS device drivers do not process  IOCTL strings, and you must
 determine whether the specific driver accepts the command. If the driver
 does not process  IOCTL strings, BASIC generates the error message Illegal
 function call.


 Note

 BASIC devices (LPT n, COM n, SCRN, CONS, PIPE) and DOS block devices (A
 through Z) do not support  IOCTL.

 The  IOCTL statement is not available in OS-2 protected mode. However, you
 can achieve the same effect by directly invoking the DosDevIOCtl OS-2
 function.


 See Also

  IOCTL$ Function


 Example

 See the  IOCTL$ function programming example, which shows how the  IOCTL
 statement and the  IOCTL$ function are used with a device driver.