ioctl - Controls devices
... /* arg */);
Interfaces documented on this reference page conform to industry standards
Refer to the standards(5) reference page for more information about indus-
try standards and associated tags.
fildes Specifies the file descriptor of the requested device.
request Specifies the ioctl command to be performed on the device.
arg Specifies parameters for this request. The type of arg is depen-
dent on the specific ioctl() request and device to which the
ioctl is targeted. See the appropriate Section 7 reference page
or the documentation accompanying the device for more informa-
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 parameters 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() sys-
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 indicate
The ioctl() function sets errno to the specified values for the following
[EBADF] The fildes parameter is not a valid open file descriptor.
[EINTR] A signal was caught during the ioctl() operation.
[EINVAL] The STREAM or multiplexer referenced by fildes is linked
(directly or indirectly) downstream from a multiplexer.
If an underlying device driver detects an error, errno may be set to one of
the following values:
[EINVAL] Either the request or arg parameter is not valid.
[EIO] Some physical I/O error has occurred.
[ENOTTY] 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 specification.)
[ENOTTY] [Tru64 UNIX] The fildes parameter is not associated with a char-
acter special device, or the specified request does not apply to
the kind of object that the fildes parameter references.
[ENXIO] The request and arg parameters are valid for this device driver,
but the service requested cannot be performed on the particular
[ENODEV] The fildes parameter refers to a valid STREAMS device, but the
corresponding device driver does not support the ioctl() func-
Functions: exec(2), fcntl(2)
Files: tty(7), nifftmt(7), streamio(7)