IOCTL(2)                      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
     character 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.

BSD 4                          December 11, 1993                         BSD 4