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_IOW(9r)
NAME
  _IOW - General: Defines ioctl types for device control operations

SYNOPSIS
  #include <sys/ioctl.h>


  _IOW(
	  g,
	  n,
	  t );

ARGUMENTS
  g   Specifies the group that this ioctl type belongs to. This argument must
      be a nonnegative 8-bit number (that is, in the range 0-255 inclusive).
      You can pass the value 0 (zero) to this argument if a new ioctl group
      is not being defined.

  n   Specifies the specific ioctl type within the group. These types should
      be sequentially assigned numbers for each different ioctl operation the
      driver supports. This argument must be a nonnegative 8-bit number (that
      is, in the range 0-255 inclusive).

  t   Specifies the size of the data passed from the user application back to
      the kernel. The kernel determines the number of bytes to transfer by
      passing the value in this argument to the sizeof operator.

DESCRIPTION
  The _IOW macro defines ioctl types for situations where data is transferred
  from the user's buffer into the kernel.  Typically, this data consists of
  device control or status information passed to the driver from the
  application program.

EXAMPLE
  The following example uses the _IOW macro to construct an ioctl called
  DN_SETCOUNT. Note that DN_SETCOUNT passes the value zero (0) for the group
  that this ioctl belongs to and the value 3 to identify the specific ioctl
  type within the group. The DN_SETCOUNT ioctl also passes the data type int,
  which the kernel passes to the sizeof operator  to determine how much data
  is passed from the user application back to the kernel.

       #define DN_SETCOUNT    _IOR(0,3,int)







SEE ALSO
  ioctl Commands: _IO(9r), _IOR(9r), _IOWR(9r)

Index for Section 9

Alphabetical listing for Special Characters

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