ioctl - control device
int ioctl(int d, int request, ...)
[The "third" argument is traditionally char *argp, and
will be so named for this discussion.]
The ioctl function manipulates the underlying device
parameters of special files. In particular, many operat
ing characteristics of character special files (e.g. ter
minals) may be controlled with ioctl requests. The argu
ment d must be an open file descriptor.
An ioctl request has encoded in it whether the argument is
an in parameter or out parameter, and the size of the
argument argp in bytes. Macros and defines used in speci
fying an ioctl request are located in the file
On success, zero is returned. On error, -1 is returned,
and errno is set appropriately.
EBADF d is not a valid descriptor.
EFAULT argp references an inaccessible memory area.
ENOTTY d is not associated with a character special
ENOTTY The specified request does not apply to the kind of
object that the descriptor d references.
EINVAL Request or argp is not valid.
No single standard. Arguments, returns, and semantics of
ioctl(2) vary according to the device driver in question
(the call is used as a catch-all for operations that don't
cleanly fit the Unix stream I/O model). See ioctl_list(2)
for a list of many of the known ioctl calls. The ioctl
function call appeared in Version 7 AT&T Unix.
execve(2), fcntl(2), mt(4), sd(4), tty(4)