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ioctl(2)							      ioctl(2)

NAME    [Toc]    [Back]

     ioctl - control device

SYNOPSIS    [Toc]    [Back]

     #include <unistd.h>
     #include <sys/ioctl.h>   /* _SGIAPI FIO* functions	*/
     #include <stropts.h>     /* STREAMS functions */

     int ioctl (int fildes, int	request, ...);

DESCRIPTION    [Toc]    [Back]

     ioctl performs a variety of control functions on devices and STREAMS.
     For non-STREAMS files, the	functions performed by this call are devicespecific
 control functions.  request and an optional third	argument with
     varying type are passed to	the file designated by fildes and are
     interpreted by the	device driver.

     For STREAMS files,	specific functions are performed by the	ioctl call as
     described in streamio(7).	Argument types and other request-specific
     information found in streamio(7) take precedence over information found
     in	this manual page.

     fildes is an open file descriptor that refers to a	device.	 request
     selects the control function to be	performed and depends on the device
     being addressed.  Many devices do not require that	the device be opened
     in	a writable mode	in order to successfully perform ioctls	that change
     the device	parameters, or even the	contents of the	media for devices with
     permanent storage.	 arg represents	a third	argument that has additional
     information that is needed	by this	specific device	to perform the
     requested function.  The data type	of arg depends upon the	particular
     control request, but it is	generally either an int	or a pointer to	a
     device-specific data structure.

     In	addition to device-specific and	STREAMS	functions, generic functions
     are provided by more than one device driver, for example, the general
     terminal interface	[see termio(7)].

     The following operations are generally available on all descriptors [see

     FIONBIO	    Enables or disables	non-blocking I/O on fildes.  arg is a
		    pointer to an int whose value should be 1 to enable	nonblocking
 I/O or 0 to disable non-blocking I/O.  This
		    operation is not currently supported on old-style (nonSTREAMS)

     FIONREAD	    Returns the	number of bytes	of data	currently available to
		    be read on fildes.	arg is a pointer to a size_t into
		    which the byte-count will be stored.

									Page 1

ioctl(2)							      ioctl(2)

     ioctl fails for any type of file if one or	more of	the following are

     EACCES	    The	type of	access requested on the	file designated	by
		    fildes is denied.

     EBADF	    fildes is not a valid open file descriptor.

     ENOTTY	    fildes is not associated with a device driver that accepts
		    control functions.

     EINTR	    A signal was caught	during the ioctl system	call.

     ioctl also	fails if the device driver detects an error.  In this case,
     the error is passed through ioctl without change to the caller.  A
     particular	driver might not have all of the following error cases.	 Under
     the following conditions, requests	to device drivers may fail and set
     errno to:

     EFAULT	    request requires a data transfer to	or from	a buffer
		    pointed to by arg, but some	part of	the buffer is outside
		    the	process's allocated space.

     EINVAL	    request or arg is not valid	for this device.

     EIO	    Some physical I/O error has	occurred.

     ENXIO	    The	request	and arg	are valid for this device driver, but
		    the	service	requested can not be performed on this
		    particular subdevice.

     ENOLINK	    fildes is on a remote machine and the link to that machine
		    is no longer active.

     ETIMEDOUT	    fildes is on a remote machine which	is not available [see

     STREAMS errors are	described in streamio(7).

SEE ALSO    [Toc]    [Back]

     streamio(7), termio(7)

DIAGNOSTICS    [Toc]    [Back]

     Upon successful completion, the value returned depends upon the device
     control function, but must	be a non-negative integer. Otherwise, a	value
     of	-1 is returned and errno is set	to indicate the	error.

									PPPPaaaaggggeeee 2222
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