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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 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.

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