vn_fullpath question.

Oliver Fromme olli at
Tue Nov 28 15:47:27 UTC 2006

Robert Watson wrote:
 > Nikolay Pavlov wrote:
 > > Hi. I am trying to extend fstat utility, so that it can use name cache to 
 > > recreate full path at least for text. I have found vn_fullpath function 
 > > usefull in this case. I am newbe in C, so it could be stupid question, but 
 > > could someone explaine what is "struct thread *td" in argument list of this 
 > > function. Is this the thread which opened the vnode initially or it is the 
 > > thread which searches for the vnode? i.e. fstat thread. In any case how i 
 > > can get this *td structure?
 > vn_fullpath(9) is a kernel API, not a user API, so can only be invoked from 
 > kernel space.  There are unimplemented, undocumented prototypes in the system 
 > call table for __getpath_fromfd() and __getpath_fromaddr(), which are 
 > presumably intended (with adequate permissions) to allow converting file 
 > descriptor indexes into paths, etc.  I think Peter dropped them in, but I'm 
 > not sure if he's posted patches.

Nikolay, you might want to have a look at the source code
of the "lsof" utility (ports/sysutils/lsof).  It is able
to display path names for file descriptors.  Maybe you can
borrow an idea from it.

It might also be worth mentioning that our friends from the
DragonFly BSD project (derived from FreeBSD 4) have added
the ability to display path names to their version of the
fstat utility.  You can look at their cvsweb here:

However, I suspect that they have also made modifications
to the kernel interfaces in order to support the fstat
utility, so their improvements to that utility might not
be applicable to FreeBSD.

Best regards

Oliver Fromme,  secnetix GmbH & Co. KG, Marktplatz 29, 85567 Grafing
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