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dribble

dribble Function

Syntax:

dribble &optional pathname → implementation-dependent

Arguments and Values:

pathname—a pathname designator .

Description:

Either binds *standard-input* and *standard-output* or takes other appropriate action, so as to send a record of the input/output interaction to a file named by pathname. dribble is intended to create a readable record of an interactive session.

If pathname is a logical pathname, it is translated into a physical pathname as if by calling translate-logical-pathname.

(dribble) terminates the recording of input and output and closes the dribble file.

If dribble is called while a stream to a “dribble file” is still open from a previous call to dribble, the effect is implementation-defined. For example, the already-open stream might be closed, or dribbling might occur both to the old stream and to a new one, or the old stream might stay open but not receive any further output, or the new request might be ignored, or some other action might be taken.

Affected By:

The implementation.

Exceptional Situations:

If a failure occurs when performing some operation on the file system while creating the dribble file, an error of type file-error is signaled.

An error of type file-error might be signaled if pathname is a designator for a wild pathname.

See Also:

Section 19.1.2 (Pathnames as Filenames)

Notes:

dribble can return before subsequent forms are executed. It also can enter a recursive interaction loop, returning only when (dribble) is done.

dribble is intended primarily for interactive debugging; its effect cannot be relied upon when used in a program.

− Variable

Value Type:

a form.

Initial Value:

implementation-dependent.

Description:

The value of - is the form that is currently being evaluated by the Lisp read-eval-print loop.

Examples:

(format t "~&Evaluating ~S~%" -) 
▷ Evaluating (FORMAT T "~&Evaluating ~S~%" -) 
→ NIL

Affected By:

Lisp read-eval-print loop.

See Also:

+ (variable), * (variable), / (variable), Section 25.1.1 (Top level loop)

Expanded Reference: dribble​

Recording a session to a file​

dribble with a pathname argument begins recording the interactive session (both input and output) to the specified file.

;; Start recording the session
;; (dribble "/tmp/session-log.txt")
;; ... interact with the REPL ...
;; All input and output is recorded to the file.

Stopping the recording​

Calling dribble with no arguments stops the recording.

;; Stop recording
;; (dribble)
;; The file /tmp/session-log.txt now contains the session transcript.

Typical usage pattern​

;; (dribble "/tmp/debug-session.txt")
;; (defun test () (+ 1 2))
;; (test)
;; (dribble)
;; Now /tmp/debug-session.txt contains:
;;   > (defun test () (+ 1 2))
;;   TEST
;;   > (test)
;;   3
;; (exact format is implementation-dependent)

Implementation-dependent behavior​

The exact behavior of dribble is implementation-dependent. Some implementations may not support it, and the format of the recorded output varies.

;; dribble returns implementation-dependent values
;; (dribble "/tmp/test.txt")
=> ; implementation-dependent
;; (dribble)
=> ; implementation-dependent