IOCTL(2)						      BSD System Calls Manual							  IOCTL(2)

NAME

     ioctl -- control device

SYNOPSIS

     #include <sys/ioctl.h>

     int
     ioctl(int fildes, unsigned long request, ...);

DESCRIPTION

     The ioctl() function manipulates the underlying device parameters of special files.  In particular, many operating characteristics of charac-
     ter special files (e.g. terminals) may be controlled with ioctl() requests.  The argument fildes 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]		fildes is not a valid descriptor.

     [EINVAL]		Request or argp is not valid.

     [ENOTTY]		fildes is not associated with a character special device.

     [ENOTTY]		The specified request does not apply to the kind of object that the descriptor fildes references.

SEE ALSO

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

HISTORY

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

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