IOCTL(2-SVR3)       RISC/os Reference Manual        IOCTL(2-SVR3)



NAME
     ioctl - control device

SYNOPSIS
     #include <bsd/sys/types.h>
     int ioctl (fildes, request, arg)
     int fildes, request;

DESCRIPTION
     ioctl 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 argu-
     ments request and arg are passed to the file designated by
     fildes and are interpreted by the device driver.  This con-
     trol is infrequently used on non-STREAMS devices, with the
     basic input/output functions performed through the read(2)
     and write(2) system calls.

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

     fildes is an open file descriptor that refers to a device.
     request selects the control function to be performed and
     will depend on the device being addressed.  arg represents
     additional information that is needed by this specific dev-
     ice 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, gen-
     eric functions are provided by more than one device driver,
     for example, the general terminal interface [see termio(7)].

     ioctl will fail for any type of file if one or more of the
     following are true:

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

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

     [EINTR]  A signal was caught during the ioctl system call.

ERRORS
     ioctl will also fail 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 will fail if one or more of the following are true:

     [EFAULT]



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IOCTL(2-SVR3)       RISC/os Reference Manual        IOCTL(2-SVR3)



          request requires a data transfer to or from a buffer
          pointed to by arg, but some part of the buffer is out-
          side the process's allocated space.

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

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

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

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          machine is no longer active.

     STREAMS errors are described in streamio(7).

SEE ALSO
     streamio(7), termio(7) in the System Administrator's Refer-
     ence Manual.

DIAGNOSTICS
     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.

























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