ioctl - Control devices
#include <stropts.h>
int ioctl(
int fildes,
int request,
... /* arg */ );
Interfaces documented on this reference page conform to
industry standards 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 parameters for request. The type of
arg is dependent on the specific request and device to
which the request is targeted. See the appropriate Section
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 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() 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 indicate the error.
The ioctl() function sets errno to the specified values
for the following 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 indirectly)
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 specification.)
[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)
ioctl(2)
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