stream-file-position

stream-file-position Accessor

Summary

Returns or changes the current position within a stream.

Package

stream

Signatures

stream-file-position stream => position

(setf stream-file-position) position-spec stream => success-p

Arguments

`stream`⇩	A stream.
`position-spec`⇩	A file position designator.

Values

`position`	A file position or `nil`.
`success-p`⇩	A generalized boolean.

Description

The accessor stream-file-position implements file-position using two generic functions stream-file-position and (setf stream-file-position).

stream-file-position is called when file-position is called with one argument.

(setf stream-file-position) is called when file-position is called with two arguments.

The return value is returned by file-position. For the setf function, this is a slight anomaly because setf functions normally return the new value. However in this case it should return success-p as mandated by the ANSI Common Lisp standard.

The default methods specializing stream on stream return nil and ignore position-spec.