[Openmcl-devel] how to query a directory to be writable in CCL Mac and Win?

Pascal J. Bourguignon pjb at informatimago.com
Wed Oct 12 19:36:14 UTC 2011


Alexander Repenning <ralex at cs.colorado.edu> writes:

> AFAIK there is no portable CL function to do this but is there some
> CCL specific way? 

Just create a file in that directory.

  (handler-case
     (progn
        (open "/some/dir/file.data" :direction :probe 
                                    :if-does-not-exist:create)
        t)
   (error () 
        nil))


> In Cocoa and Cocotron there is a function isWritable
> but it appears to be false in some cases, e.g., folders contained in
> the Application files on Windows 7, even when files appear to be
> writable in that folder. 

You could also use FFI and call access(2).  But see below.


> The only strategy, I am guessing, would be to
> actually write a temp file and test if that succeeded.

This strategy is wrong too, because while you may be able to write a
temp file, one nanosecond later another process may change the access
rights to that directory, and you won't be able to create the real file
in that directory anymore.

-- 
__Pascal Bourguignon__                     http://www.informatimago.com/
A bad day in () is better than a good day in {}.




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