Question

I ran some code like this

(defun writeFile (name content)
    (with-open-file (stream name
        :direction :output
        :if-exists :overwrite
        :if-does-not-exist :create)
    (format stream content)))
(writeFile "C:\Users\Peter\test.txt" "Test...")

but then I checked my C:\Users\Peter directory and it did not contain create a file named test.txt. What am I doing wrong?

Answer 1

\ is an escape character in strings in Common Lisp.

(length "\\") is 1.

(length "\U") is 1.

"\U" is "U".

"C:\Users\Peter\test.txt" is "C:UsersPetertest.txt".

So you are writing a file called "C:UsersPetertest.txt".

Three possible solutions:

• escape the backslash with a backslash
• I’m not sure if that works: use a forward slash
• use one of the PATHNAME functions to construct the pathname

Advanced: use a logical pathname