ioctl - control device
- include <sys/ioctl.h>
int ioctl(int d, int request,...)
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 .
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.
- d is not a valid descriptor.
- argp references an inaccessible memory area.
- d is not associated with a character special device.
- The specified request does not apply to the kind of object that the descriptor d references.
- Request or argp is not valid. This normally happens if you've provided the wrong type of request for the file descriptor you passed to the ioctl
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), netdevice(7), socket(7)