ioctl()

Control a device

Synopsis:

#include <sys/ioctl.h> 

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

Arguments:

fd

An open file descriptor for the file or device that you want to manipulate.

request

What you want to do to the file or device; see below for a summary. The macros and definitions that you use in specifying a request are located in the file <sys/ioctl.h>.

Additional arguments

As required by the request.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The ioctl() function manipulates the underlying parameters of files. In particular, it can be used to control many of the operating attributes of files (such as the attributes of terminals).

The request argument determines whether the subsequent arguments are an “in” or “out” parameter; it also specifies the size of the arguments in bytes.

How ioctl() commands map to other commands

Some ioctl() commands map to calls to fcntl(), tcgetattr(), tcsetattr(), and tcsetsid(). Other commands are transformed into a different devctl() command, and the rest are simply passed to devctl(). Here's a summary:

---

If you're writing a resource manager, note that the iofunc_devctl_default() function handles the DCMD_ALL_GETFLAGS and DCMD_ALL_SETFLAGS commands; your resource manager will need to handle all other devctl commands that apply to it.

---

Returns:

A value based on the request, or -1 if an error occurs (errno is set).

Errors:

EBADF

Invalid descriptor fd.

EINVAL

The request or optional variables aren't valid.

ENOTTY

The fd argument isn't associated with a character special device; the specified request doesn't apply to the kind of object that the descriptor fd references.

Classification:

POSIX 1003.1 XSR

Caveats:

The ioctl() function is a Unix function that varies greatly from platform to platform.

See also:

devctl(), fcntl(), tcgetattr(), tcsetattr(), tcsetsid().