common-lisp Streams Reading and writing entire files to and from strings
Example
The following function reads an entire file into a new string and returns it:
(defun read-file (infile)
(with-open-file (instream infile :direction :input :if-does-not-exist nil)
(when instream
(let ((string (make-string (file-length instream))))
(read-sequence string instream)
string))))
The result is NIL if the file does not exists.
The following function writes a string to a file. A keyword parameter is used to specify what to do if the file already exists (by default it causes an error, the values admissible are those of the with-open-file macro).
(defun write-file (string outfile &key (action-if-exists :error))
(check-type action-if-exists (member nil :error :new-version :rename :rename-and-delete
:overwrite :append :supersede))
(with-open-file (outstream outfile :direction :output :if-exists action-if-exists)
(write-sequence string outstream)))
In this case write-sequence can be substituted with write-string.
