ioctl man page on OpenBSD

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IOCTL(2)		  OpenBSD Programmer's Manual		      IOCTL(2)

     ioctl - control device

     #include <sys/ioctl.h>

     ioctl(int d, unsigned long request, ...);

     The ioctl() function manipulates the underlying device parameters of
     special files.  In particular, many operating characteristics of
     character special files (e.g., terminals) may be controlled with ioctl()

     The argument d must be an open file descriptor.  The third argument is
     called arg and contains additional information needed by this device to
     perform the requested function.  arg is either an int or a pointer to a
     device-specific data structure, depending upon the given request.

     An ioctl request has encoded in it whether the argument is an ``in''
     parameter or ``out'' parameter, and the size of the third argument (arg)
     in bytes.	Macros and defines used in specifying an ioctl request are
     located in the file <sys/ioctl.h>.

     Some ioctls are applicable to any file descriptor.	 These include:

	     Set close-on-exec flag.  The file will be closed when exec(3) is

	     Clear close-on-exec flag.	The file will remain open across

     Some generic ioctls are not implemented for all types of file
     descriptors.  These include:

     FIONREAD int
	     Get the number of bytes that are immediately available for

     FIONBIO int
	     Set non-blocking I/O mode if the argument is non-zero.  In non-
	     blocking mode, read(2) or write(2) calls return -1 and set errno
	     to EAGAIN immediately when no data is available.

     FIOASYNC int
	     Set asynchronous I/O mode if the argument is non-zero.  In
	     asynchronous mode, the process or process group specified by
	     FIOSETOWN will start receiving SIGIO signals when data is
	     available.	 The SIGIO signal will be delivered when data is
	     available on the file descriptor.

	     Set/get the process or the process group (if negative) that
	     should receive SIGIO signals when data is available.

     If an error has occurred, a value of -1 is returned and errno is set to
     indicate the error.

     ioctl() will fail if:

     [EBADF]	   d is not a valid descriptor.

     [ENOTTY]	   d is not associated with a character special device.

     [ENOTTY]	   The specified request does not apply to the kind of object
		   that the descriptor d references.

     [EINVAL]	   request or arg is not valid.

     [EFAULT]	   arg points outside the process's allocated address space.

     cdio(1), chio(1), mt(1), execve(2), fcntl(2), intro(4), tty(4)

     An ioctl() function call appeared in Version 7 AT&T UNIX.

OpenBSD 4.9			 May 31, 2007			   OpenBSD 4.9

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