IOCTL(2)                  386BSD Programmer's Manual                  IOCTL(2)

NAME
     ioctl - control device

SYNOPSIS
     #include <sys/ioctl.h>

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

DESCRIPTION
     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>.

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:

     [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
     execve(2),  fcntl(2),  mt(4),  tty(4),  intro(4)

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

4th Berkeley Distribution       March 10, 1991                               1