IOCTL(2) BSD System Calls Manual IOCTL(2)
ioctl - control device
ioctl(int d, unsigned long request, ...);
The ioctl() function manipulates the underlying device parameters of spe-
cial 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. The third argument is
called arg and contains additional information needed by this device to
perform the requested function. arg is either an int or a pointer to a
device-specific data structure, depending upon the given request.
An ioctl request has encoded in it whether the argument is an ``in''
parameter or ``out'' parameter, and the size of the third argument (arg)
in bytes. Macros and defines used in specifying an ioctl request are
located in the file <sys/ioctl.h>.
If an error has occurred, a value of -1 is returned and errno is set to
indicate the error.
ioctl() will fail if:
[EBADF] d is not a valid descriptor.
[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 arg is not valid.
[EFAULT] arg points outside the process's allocated address
cdio(1), chio(1), mt(1), execve(2), fcntl(2), intro(4), tty(4)
An ioctl() function call appeared in Version 7 AT&T UNIX.
BSD December 11, 1993 BSD