ioctl man page on DigitalUNIX

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ioctl(2)							      ioctl(2)

       ioctl - Control devices

       #include <stropts.h>

       int ioctl(
	       int fildes,
	       int request,
	       ... /* arg */ );

       Interfaces  documented on this reference page conform to industry stan‐
       dards as follows:

       ioctl(): XSH4.2, XSH5.0

       Refer to the standards(5) reference page	 for  more  information	 about
       industry standards and associated tags.

       Specifies  the  file descriptor of the requested device.	 Specifies the
       ioctl() request to be performed on the device.  Specifies  the  parame‐
       ters  for request. The type of arg is dependent on the specific request
       and device to which the request is targeted.  See the appropriate  Sec‐
       tion  7 reference page or the documentation accompanying the device for
       more information.

       The ioctl() function performs a variety of control functions on devices
       and  STREAMS.  For  non-STREAMS	files, the functions performed by this
       call are device-specific control functions. The request and arg parame‐
       ters are passed to the file designated by fildes and are interpreted by
       the device driver. This control is  occasionally	 used  on  non-STREAMS
       devices,	 with  the  basic input/output functions performed through the
       read() and write() system calls.

       An ioctl() request has encoded in it whether the parameter is  an  "in"
       parameter  or  "out"  parameter,	 and  the size of the arg parameter in
       bytes. Macros and defines  used	to  specify  an	 ioctl()  request  are
       located in the <stropts.h> header file.

       For  STREAMS  files,  specific  functions  are performed by the ioctl()
       function as described in streamio(7).

       STREAMS errors are described in streamio(7).

       Upon successful completion, the ioctl() function returns a value	 other
       than -1 that depends upon the STREAMS device control function.

       If an error occurs, a value of -1 is returned and errno is set to indi‐
       cate the error.

       The ioctl() function sets errno to the specified values for the follow‐
       ing  general  conditions: The fildes parameter is not a valid open file
       descriptor.  A signal was caught during	the  ioctl()  operation.   The
       STREAM or multiplexer referenced by fildes is linked (directly or indi‐
       rectly) downstream from a multiplexer.

       If an underlying device driver detects an error, errno may  be  set  to
       one of the following values: Either the request or arg parameter is not
       valid.  Some physical I/O error has occurred.  The fildes parameter  is
       not  associated	with  a STREAMS device that accepts control functions.
       (Defined for Issue 4 Version 2 and higher issues of the XSH  specifica‐
       tion.)	[Tru64	UNIX]  The  fildes  parameter is not associated with a
       character special device, or the specified request does	not  apply  to
       the  kind  of object that the fildes parameter references.  The request
       and arg parameters are valid for this device driver,  but  the  service
       requested  cannot be performed on the particular subdevice.  The fildes
       parameter refers to a  valid  STREAMS  device,  but  the	 corresponding
       device driver does not support the ioctl() function.

       Functions: exec(2), fcntl(2)

       Files: proc(4) tty(7), nifftmt(7), streamio(7)

       Standards: standards(5)


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