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stream-external-format

stream-external-format Function

Syntax:

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 
<i><sup>or</sup>→</i> :ISO8859/1-1987 
<i><sup>or</sup>→</i> (:ASCII :SAIL) 
<i><sup>or</sup>→</i> ACME::PROPRIETARY-FILE-FORMAT-17 
<i><sup>or</sup>→</i> #<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.

Expanded Reference: stream-external-format​

Basic Usage​

stream-external-format returns an external file format designator for a file stream. The only standardized value is :DEFAULT.

(with-open-file (s "/tmp/cl-sef-test.txt"
                   :direction :output :if-exists :supersede)
  (stream-external-format s))
=> :UTF-8

Implementation-Dependent Values​

The returned value is implementation-dependent and may vary. It could be a keyword, list, or other object.

;; The following shows what a particular implementation might return.
;; Actual results vary:
;; :DEFAULT
;; :UTF-8
;; :ISO-8859-1
;; (:ASCII :SAIL)

With Explicit External Format​

When opening a file with an explicit external format, stream-external-format reflects that choice.

(with-open-file (s "/tmp/cl-sef-test.txt"
                   :direction :output
                   :if-exists :supersede
                   :external-format :default)
  (stream-external-format s))
=> :UTF-8

Not Meaningful for Binary Streams​

The external format is meaningful for character streams. For binary streams, the result is implementation-dependent.