Thanks Byron, a good tip.
On May 17, 2008, at 11:04 AM, Byron Nevins wrote:
> Say you are given a java.io.File object that was made like so:
>
> File f = new File("/foo/./././goo");
>
> Say that you need a File object for the parent dir -- which is "/
> foo" in this case.
>
> If you do this:
>
> File parent = f.getAbsoluteFile().getParentFile()
>
> parent will be "/foo/././"
> File grandparent = parent.getParentFile()
>
> grandparent will be "/foo/."
>
> I.e. getParent and getParentFile are pretty dumb. They just strip
> off the last path seperator without looking at it.
>
> Now if you do the following with the original file, you get the
> "real" parent dir. This is the trick.
>
> File parent = new File(f, "..");
> parent --> "/foo"
>
> ------------------------------
> I.e. never call getParent or getParentFile -- it will not work with
> relative path portions.
> instead use the File constructor with ".." as the filename.
> -------------------------------
>
> Another possible solution is to sanitize the original File with
> getCanonicalFile() to get rid of the relative path portions.
> this has 3 problems -
>
> 1) Your path will have error-prone and unneccessary (usually)
> backslashes in Windows
> 2) It's more work and requires a try/catch block
> 3) It handles symbolic link files differently
>
> The reason I'm sending this tip out is that I got burned by this
> behavior. I had code that was getting a crucial parent directory.
> It was working fine for months. Then in code a hundred levels above
> it, a "." was inserted just before the final directory name. KABOOM.
>
> Ref: http://bt2ws.central.sun.com/CrPrint?id=6687287
> --
> Byron Nevins Work 408-276-4089, Home 650-359-1290, Cell 650-784-4123
> - Sun Microsystems, Inc.
---
Lloyd L Chambers
lloyd.chambers_at_sun.com
Sun Microsystems, Inc