ioctl(2)ioctl(2)NAMEioctl - Control devices
... /* 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
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)