Experimental Physics and
Industrial Control System

[email protected] (Ralph Lange) · Tue, 24 Jun 1997 12:12:47 +0200 (METDST)

> Sort of...  Here's an excerpt from the VxWorks FAQ that addresses the
> issue:
> 
> ------------------------------
> 
> 19.  Why can't I do ".." at top level directories or NFS mount points?
> 
> Because, again, VxWorks does not really have a "filesystem" as most people
> understand it.  The top level directories are just implemented as device
> driver "node", which is used to identify the ioDev associated with the
> specific VxWorks "filesystem".  Since there is no underlying filesystem
> layer, the story ends there.  When you're at the top of the directory
> hierarchy within a given ioDev/filesytem, you simply cannot do "..".
> 
> ------------------------------
> 
> 20. Why do I have trouble using relative symbolic links with NFS?
> 
> See [Q: Why can't I do ".." at top level directories or NFS mount points?]
> above.  This is just another problem caused by the fact that a real filesystem
> does not exist for VxWorks.  NFS client implementation actually does implement
> the symbolic links correctly, using lookup and readlink.  The problem is
> due to the fact that, for some relative links that use ".." or whatever, that
> crosses over filesystems, VxWorks cannot have underlying subsystem that will
> handle file pathname to device mapping.  
> 
> Using absolute symbolic links work just fine (i.e. full path name from top).
> 
> ------------------------------

Thanks a lot.

But:

I'm using an absolute symbolic link, i.e. simple string replacement when
processing the link would result in the correct path. (Still the problem
might be due to the file system crossing.) And - I forgot to tell -
reading a file works perfectly, just writing produces the error.

Do you think this fits the FAQ explanation?

Ralph
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System