ioctl(2) — CLIX 3.1r7.6.28



  ioctl(2)                            CLIX                            ioctl(2)



  NAME

    ioctl - Control device

  LIBRARY

    Standard C Library (libc.a)

  SYNOPSIS

    int ioctl(
      int fildes ,
      int request );

  PARAMETERS

    fildes   Represents a file descriptor.

    request  Represents a request.

    arg      Requests specific data, either a pointer to a device-specific
             data structure or an integer flag.

  DESCRIPTION

    The ioctl() function performs a variety of control functions on devices
    and STREAMS.  For non-STREAMS files, the functions performed by this call
    are device-specific control functions.  The request and arg parameters are
    passed to the file designated by fildes and are interpreted by the device
    driver.  This control is infrequently used on non-STREAMS devices, with
    the basic input/output functions performed through the read() and write()
    functions.

    For STREAMS files, specific functions are performed by ioctl() as
    described in streamio(7).

    The fildes parameter is an open file descriptor that refers to a device.
    The request parameter selects the control function to be performed and
    will depend on the device being addressed.  The arg parameter represents
    additional information that is needed by this specific device to perform
    the requested function.  The data type of arg depends upon the particular
    control request, but it is either an integer or a pointer to a device-
    specific data structure.

    In addition to device-specific and STREAMS functions, generic functions
    are provided by more than one device driver, such as the general terminal
    interface.  (See the termio command.)

  EXAMPLES

    To perform a PUSH function on an open stream:



  2/94 - Intergraph Corporation                                              1



  ioctl(2)                            CLIX                            ioctl(2)



    if (ioctl(stream_fd, I_PUSH, module_name) == -1)
         perror("ioctl PUSH failed");


  RETURN VALUES

    Upon successful completion, the value returned depends upon the device
    control function, but must be a non-negative integer.  Otherwise, a value
    of -1 is returned and errno is set to indicate the error.

  ERRORS

    The ioctl() function fails for any type of file if one or more of the
    following are true:

    [EBADF]    The fildes parameter is not a valid open file descriptor.

    [ENOTTY]   The value of fildes is not associated with a device driver that
               accepts control functions.

    [EINTR]    A signal was caught during the ioctl() function.

    The ioctl() function also fails if the device driver detects an error.  In
    this case, the error is passed through ioctl() without change to the
    caller.  A particular driver might not have all of the following error
    cases.  Other requests to device drivers fail if one or more of the
    following are true:

    [EFAULT]    The value of request requires a data transfer to or from a
                buffer pointed to by arg, but some part of the buffer is
                outside the process's allocated space.

    [EINVAL]    The value of request or arg is not valid for this device.

    [EIO]       Some physical I/O error has occurred.

    [ENXIO]     The request and arg parameters are valid for this device
                driver, but the service requested can not be performed on this
                particular subdevice.

    [ENOLINK]   The specified fildes is on a remote machine and the link to
                that machine is no longer active.

    STREAMS errors are described in streamio().

  RELATED INFORMATION

    Files:  streamio(7), termio(7), termios(7)






  2                                              Intergraph Corporation - 2/94

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