#### 21.2.30 stream-external-format [Function]

`stream-external-format` stream ⇒ format

#### Arguments and Values::

stream—a file stream.

format—an external file format.

#### Description::

Returns an external file format designator for the stream.

#### Examples::

     (with-open-file (stream "test" :direction :output)
       (stream-external-format stream))
    ⇒  :DEFAULT
    OR⇒ :ISO8859/1-1987
    OR⇒ (:ASCII :SAIL)
    OR⇒ ACME::PROPRIETARY-FILE-FORMAT-17
    OR⇒ #<FILE-FORMAT :ISO646-1983 2343673>

#### See Also::

the `:external-format` argument to the function open and the with-open-file macro.

#### Notes::

The format returned is not necessarily meaningful to other implementations.