The Get Device/Volume Information routine provides a simplified
    interface to the $GETDVI system service. It returns information
    about the primary and secondary device characteristics of an I/O
    device. The calling process need not have a channel assigned to
    the device about which it wants information.

    Format

      LIB$GETDVI  item-code [,channel] [,device-name]

                  [,longword-integer-value] [,resultant-string]

                  [,resultant-length] [,pathname]

1  –  Returns

    OpenVMS usage:cond_value
    type:         longword (unsigned)
    access:       write only
    mechanism:    by value

2  –  Arguments

 item-code

    OpenVMS usage:longword_signed
    type:         longword (signed)
    access:       read only
    mechanism:    by reference

    Code specifying the item of information you are requesting. The
    item-code argument is the address of a signed longword containing
    the item code. All valid $GETDVI item codes whose names begin
    with DVI$_ are accepted.

 channel

    OpenVMS usage:channel
    type:         word (unsigned)
    access:       read only
    mechanism:    by reference

    OpenVMS I/O channel assigned to the device for which LIB$GETDVI
    returns information. The channel argument is the address of an
    unsigned word containing the channel specification. If channel is
    not specified, device-name is used instead. You must specify
    either channel or device-name, but not both. If neither is
    specified, the error status SS$_IVDEVNAM is returned.

 device-name

    OpenVMS usage:device_name
    type:         character string
    access:       read only
    mechanism:    by descriptor

    Name of the device for which LIB$GETDVI returns information.
    The device-name argument is the address of a descriptor pointing
    to the device name string. If this string contains a colon, the
    colon and the characters that follow it are ignored.

    The device-name may be either a physical device name or a logical
    name. If the first character in the string is an underscore
    character (_),  the name is considered a physical device name.
    Otherwise, the name is considered a logical name, and logical
    name translation is performed until either a physical device name
    is found or the system default number of translations has been
    performed.

    If device-name is not specified, channel is used instead. You
    must specify either channel or device-name, but not both. If
    neither is specified, the error status SS$_IVDEVNAM is returned.
    The device name must not be longer than 255 characters.

 longword-integer-value

    OpenVMS usage:longword_signed
    type:         longword (signed)
    access:       write only
    mechanism:    by reference

    Numeric value of the information requested. The longword-integer-
    value argument is the address of a signed longword containing the
    numeric value. If an item is listed as only returning a string
    value, this argument is ignored.

 resultant-string

    OpenVMS usage:char_string
    type:         character string
    access:       write only
    mechanism:    by descriptor

    String representation of the information requested. The
    resultant-string argument is the address of a descriptor pointing
    to this information. If resultant-string is not specified and if
    the value returned has only a string representation, the error
    status LIB$_INVARG is returned.

 resultant-length

    OpenVMS usage:word_unsigned
    type:         word (unsigned)
    access:       write only
    mechanism:    by reference

    Number of significant characters written to resultant-string by
    LIB$GETDVI. The resultant-length argument is the address of an
    unsigned word containing this length.

 pathname

    OpenVMS usage:path_name
    type:         character text string
    access:       read only
    mechanism:    by descriptor

    (I64 and Alpha only) The name of the path about which $GETDVI
    is to return information. The pathname argument is the address
    of a character string descriptor pointing to this name string.
    The path name may be used with either the channel or device-name
    arguments.

    Check the definitions of the item codes to see if the pathname
    argument is used. In general, item codes that return information
    that may vary by path will make use of the pathname argument.
    The paths for a multipath device can be seen with the SHOW DEVICE
    /FULL command, the SYS$DEVICE_PATH_SCAN system service, or the
    F$MULTIPATH DCL lexical function.

    If the pathname argument is used, it will be validated against
    the existing paths for the device specified. If the path does
    not exist, the error SS$_NOSUCHPATH will be returned, even if the
    item codes(s) used do not make use of the pathname argument.