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(tye)Re: FIFO directory?
by tye (Sage) on Jun 18, 2001 at 18:31 UTC
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Sure, just rewrite nfsd in Perl. See
RFC 1813
for more info.
-
tye
(but my friends call me "Tye")
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Re: FIFO directory?
by jeroenes (Priest) on Jun 18, 2001 at 15:26 UTC
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Comments:
- This is really off-topic
- I don't see how your question relates to a First In First
Out queue.
- You actually want to hack the filesystem. Luckily for
you, there is a beautiful filesystem with source code handy,
ext2fs. Brought to you by the Linux Corporation. Just
ask about it at cmonks.org
- I'm sure you can get similar functionality with some
perl script, but than you have to drop the demand that the
output is visible through any filesystem access. If you
won't mind that, please describe your problem in more
detial.
Jeroen
"We are not alone"(FZ)
Update: Maybe it is possible, but you don't tell us
what kind of data you want to provide. For example,
it's simple to replace 'ls' by a perlscript that gathers
some data about a file, and displays that besides the
filesystem data. | [reply] |
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In addition to ext2fs, there's the Perl Filesystem. I don't purport to understand it myself, but there it is.
-- Frag.
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I think maybe your missing what I'am trying to get at.
This is more of an "Is it possible" question than anything
else. A Virtual Filesystem is one way of explaining it. I
just would like to provide directory data dynamicly with perl.
But then agian it may not be possible with out going through
the rigors of writing a kernel module which is way out side
the scope of the question, if this where so then the answer
would be a simple "No, you can't do that in perl".
Brought to you by that crazy but lovable guy... lindex
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Re: FIFO directory?
by knobunc (Pilgrim) on Jun 18, 2001 at 18:46 UTC
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The reason this is a FIFO is that you can have 'named pipes' in UNIX where the file is connected directly to a process that can read or write to it. Some people use this to make their finger information cycle dynamically each time they are fingered, or to do a 'back finger' to work out who fingered them. However, there are more modern finger daemons that can run scripts directly so that particular application is less common.
The reason that a directory like fifo would be useful is to allow access to a program through a file system like interface. This would allow some funky stuff to occur. So you could map a DB directly to some filesystem layout so that reads and writes would access the DB (I think Oracle has something like this). Or you could have a filesystem that automatically version controlled files that were stored in it (e.g. Clearcase). Or you could present a dynamic view of processes running & use the OS permissions structures to controll access (e.g. the proc filesystem). Or make a directory that was mapped to a different site using FTP or HTTP. Or to store the files encrypted on disk and automatically show the desrypted version once the program has been run with the appropriate arguments.
Unfortunately there is no easy way to do this. There are some things you can do under Linux to allow a program to act as a filesystem (userfs) but that is pretty hard core. And you would probably have to write a layer in C that would map the lower level stuff up into Perl.
Tye's idea of using nfs to do this is pretty cunning and is used by some encryption filesystems. NFS basically takes a filesytem request and shoves it over the network to a program (typically nfsd) running on some remote host. The standard nfsd maps this to a local file system operation. You might be able to find an nfsd that allows you to hook into it and override the operations. Then if you run it on the same host, you can mount some arbitrary directory against your hacked nfsd and present whatever virtual view of the world that you want.
Good luck.
-ben
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you said ...
The reason that a directory like fifo would be useful is to allow access to a program through a file system like interface. This would allow some funky stuff to
occur. So you could map a DB directly to some filesystem layout so that reads and writes would access the DB ...
You hit the nail on the head with that one, that's exactly what I am aiming at only you
phrased in much more elequently than I.
I am going to keep working on this, I will keep pm.org updated.
Maybe at some point or another we will have a setup of Tie:: modules to provide
access to a user maped filesystem :)
Brought to you by that crazy but lovable guy... lindex
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Re: FIFO directory?
by Gloom (Monk) on Jun 18, 2001 at 15:23 UTC
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Hum ... I think that you wanna make something like "proc" virtual filesystem isn't it ? So the only way to do this under linux ( i think ) is a module ( kernel module, not perl module :) thus is not a perl question. Maybe take a look to proc source in the linux kernel.
_______________________
Hope this helps | [reply] |
Re: FIFO directory?
by mugwumpjism (Hermit) on Jun 18, 2001 at 18:19 UTC
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