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

     ioctl -- control device

     #include <sys/ioctl.h>

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

     The ioctl() function manipulates the underlying device parameters of spe-cial special
     cial 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>.

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

     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

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

     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.

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