with-open-stream (var stream)
{declaration}*
{form}*
⇒ {result}*
| 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).