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 operating characteristics of character
special files (e.g. terminals) may be controlled with ioctl requests.
The argument 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 specifying an ioctl request are located in
the file <sys/ioctl.h>.
Usually, on success zero is returned. A few ioctls use the return
value as an output parameter and return a nonnegative value on success.
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 device.
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), ioctl_list(2), mt(4), sd(4), tty(4)
BSD Man Page 1993-07-23 IOCTL(2)
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