CLISP - an ANSI Common Lisp

> * Pascal Bourguignon <cwo@...> [2005-07-16 20:52:51 +0200]:
>
> The parameter :supersede and :rename-and-delete don't seem to have the
> specified effect (no new file is created):
>
> [83]> (defun get-filename-identifier (Filename)
>   "Given a filename, return (cons dev inode) associated with that filename."
>   (when (probe-file filename)
>     (cons (POSIX:file-stat-dev (POSIX:file-stat filename))
>           (POSIX:file-stat-ino (POSIX:file-stat filename)))))
> GET-FILENAME-IDENTIFIER
> [84]> (let ((testfile "testfile"))
>   (flet ((test (if-exist)
>            (sleep 1)
>            (with-open-file (output-stream testfile :direction :output
>                                           :if-exists if-exist
>                                           :if-does-not-exist :create)
>              (format output-stream "random line ~A~%" (random 1000)))
>            (ext:shell "ls -li testfile")
>            (prog1 (prin1 (get-filename-identifier testfile)) (terpri))))
>     (test :overwrite)
>     (test :rename-and-delete)
>     (test :supersede))
>   (values))
> 1148057 -rw-r--r--    1 pjb      pjb            20 2005-07-16 20:48 testfile
> (774 . 1148057)
> 1148057 -rw-r--r--    1 pjb      pjb            15 2005-07-16 20:48 testfile
> (774 . 1148057)
> 1148057 -rw-r--r--    1 pjb      pjb            16 2005-07-16 20:48 testfile
> (774 . 1148057)

IMO, inode number is irrelevant here.
:rename-and-delete and :supersede are intended to make the old file
content available until the new file is closed.

e.g.

(delete-file "foo")
(with-open-file (o "foo" :direction :output :if-exist :error)
  (write-line "original" o))
(let ((lines ()))
  (with-open-file (i "foo" :direction :input)
    (push (read-line i) lines) (file-position i :start)
    (with-open-file (o "foo" :direction :output :if-exist :supersede)
      (push (read-line i) lines) (file-position i :start)
      (write-line "new" o))
    (push (read-line i) lines))
  (with-open-file (i "foo" :direction :input)
    (push (read-line i) lines))
  lines)
==> ("original" "original" "original" "new")

I am not sure about the exact difference between :rename-and-delete and
:supersede and how it affects the third member of LINES, but OPEN
<http://www.lisp.org/HyperSpec/Body/fun_open.html> says "do something
reasonable in the context of the host operating system".
the only thing that comes to mind which is not yet done by CLISP is
postponing file deletion until CLOSE.

-- 
Sam Steingold (http://www.podval.org/~sds) running w2k
<http://ffii.org/> <http://www.camera.org>
<http://www.palestinefacts.org/> <http://www.iris.org.il>
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lIDSTnlibn

Surendra Singhi wrote:
>2. If it is a pointer than use ffi:c-pointer.
>    Exception: for char* use c-string.
>3. If it is an array, but dimensions are not given then use=20
>c-pointer, else if
>dimensions are given then use c-array with the dimensions.

How do you deal with seed48()?
stdlib.h says:
extern unsigned short int *seed48 (unsigned short int __seed16v[3]) =
__THROW;

I mean, be careful about the difference between known array dimensions =
within struct definitions and function parameters!

More precisely, within struct you need the (c-array x dim), within a =
function you need an extra c-ptr around it.

modules/bindings/glibc/linux.lisp contains:
(def-call-out seed48 (:arguments (seed16v (c-ptr (c-array ushort 3))))
  (:return-type (c-ptr (c-array ushort 3)) :none))

Regards,
	J=F6rg h=F6hle.