int
     ioctl(int d, unsigned long request, char *argp);

DESCRIPTION

     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.

     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>.

RETURN VALUES

     If an error has occurred, a value of -1 is returned and errno is set to
     indicate the error.

ERRORS

     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 argp is not valid.

SEE ALSO

     mt(1), cdio(1), chio(1), execve(2), fcntl(2), tty(4), intro(4)

HISTORY

     An ioctl() function call appeared in Version 7 AT&T UNIX.

4th Berkeley Distribution      December 11, 1993     4th Berkeley Distribution