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# ioctl

    IOCTL(2)                      System Calls Manual                     IOCTL(2)

    NAME
         ioctl - control device

    SYNOPSIS
         #include <sys/ioctl.h>

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

    DESCRIPTION
         The ioctl() function manipulates the underlying device parameters of spe-
         cial 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. The third argument is
         called arg and contains additional information needed by this device to
         perform the requested function.  arg is either an int or a pointer to a
         device-specific data structure, depending upon the given request.

         An ioctl request has encoded in it whether the argument is an ``in''
         parameter or ``out'' parameter, and the size of the third argument (arg)
         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]            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 arg is not valid.

         [EFAULT]           arg points outside the process's allocated address
                            space.

    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                            December 11, 1993                           BSD

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