Re: [Nautilus-list] Directory change signals?

[David Bishop <david bishop dhs org>]

My email has been broken for a day, so I don't know if this has already been 
brought up, but fam the user-space daemon can be combined with "imon" to do 
exactly what you guys are talking about. Fam, buy itself, does not require 
any kernel changed at all, and does, in fact, monitor the entire file system 
(not just specifcally requested ones).  If kernel level support is not 
implemented, it falls back to a polling mode, so that any *nix can run fam.  
However, if you are running linux, you can install the imon patch that allows 
any file-system changes to be reported directly to fam, and from there to 
your program (nautilus, efm, whatever).  The reason I bring up efm 
(Englitenment's file manager) is because that is exactly what they are using, 
and it works great.  They have people on solaris, freebsd (that's be me!), 
and of course linux, all of which can run it, and get the benefits of real-
time or very-close-to-real-time updates. As is mentioned below this, fam and 
imon are available from sgi, and I would highly recommend talking to some sgi 
and enlightenment folks regarding how it works and where they see the 
development going. To sum up: fam doesn't *require* a kernel patch, though it 
runs better with one, and as such it is defintely worth a close inspection. 

Hope this helps,

d.a.bishop

>"Karl M. Hegbloom" wrote:
>>  It would be neat if a program could register itself with the OS
>>  kernel in some way, asking to be informed of any modifications made
>>  by other processes to the contents of a directory.
>> 
>>  How would that work?  A signal?  `poll' or `select' on the DIR?

>Exactly how this will work is very contentious (though it may have been
>resolved since I last checked). The functionality is not in the kernel
>but exists in some other Unix kernels like SGI's. It seems likely (to
>me) that given the strong end-user potential this has, unlike other
>kernel changes, this will be something that is pushed into the next
>development branch. I was sort of hoping it would make 2.4, but
>obviously it hasn't :-(

>>  Can Linux already do that?

>However, that said SGI has actually released a version of their file
>alteration monitor "fam" (which I believe runs in user-space, but you
>have to register a specific set of files for it to monitor), and on a
>larger scale a kernel-mode inode monitor. Patches for standard kernels
>exist at http://oss.sgi.com/projects/fam/ that include these. We would
>have *loved* to use such functionality in Nautilus, but we didn't feel
>it was a good idea to require kernel modules to ship with our program.
>If you are interested, one possibility would be to integrate this
>functionality as an optional extra into gnome-vfs so that kernels that
>*do* have it gnome-vfs and hence nautilus will work more "perfectly".

>-Seth


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