|open filename &key direction element-type if-exists if-does-not-exist external-format &aux direction if-does-not-exist if-exists||[Function]|
Return a stream which reads from or writes to filename. Defined keywords:
- One of :input, :output, :io, or :probe.
- Type of object to read or write, default base-char.
- The external format to use. The default value is :default for which the value of ext:*default-external-format* is used. The external format may be a keyword representing a character set to use for character streams. For local file streams, the external format may also be a list of formats that convert from the desired character or binary stream to the binary stream read and/or written to the file. Leading character based formats are ignored for binary streams.
- One of :error, :new-version, :rename, :rename-and-delete, :overwrite, :append, :supersede or nil.
- One of :error, :create or nil.
See the ANSI CL manual for details.