var — a variable name.

stream — a form; evaluated to produce a stream.

declaration — a declare expression; not evaluated.

forms — an implicit progn.

results — the values returned by the forms.

with-open-stream performs a series of operations on stream, returns a value, and then closes the stream.

Var is bound to the value of stream, and then forms are executed as an implicit progn. stream is automatically closed on exit from with-open-stream, no matter whether the exit is normal or abnormal. The stream has dynamic extent; its extent ends when the form is exited.

The consequences are undefined if an attempt is made to assign the the variable var with the forms.

(with-open-stream (s (make-string-input-stream "1 2 3 4")) 
   (+ (read s) (read s) (read s))) → 6

The stream is closed (upon exit).

close