Writing /proc type programs

Geoff Russell · n00b Joined: 28 Apr 2004 Posts: 16

As I understand it, when a program reads a file in /proc, there is no actual file, just a program that gets called to simulate a
file. Can the same functionality be achieved outside of
the /proc filesystem?

I want to point a Crystal Reports ODBC XML driver at
a file and have my program called to generate the contents
on the fly based on the name of the file which the
driver opens.

Any pointers in the right direction will be greatly appreciated.

scarr · Posted: Tue Jan 11, 2005 1:48 am Post subject:

This would depend on how the Crystal Reports XML driver works.

More than likely it doesn't execute the file, it just reads from it. What you could do though is write your program to populate the file before the report is run.

/proc is part of the linux kernel. So it knows what to run when a file is called from that directory. If you used the XML ODBC driver it would have to know that the file is a script or program and run it to get the output.
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Geoff Russell · n00b Joined: 28 Apr 2004 Posts: 16

The whole aim is precisely not to do anything until the
report accesses the file - at which point a program would
be called to generate the required data.

cat /proc/timetable/north would generate
xml data for the CURRENT state of the northern timetable.

My understanding of the driver is that yes, it just reads
files - and I have no control over its operations (not being
open source!).

alv · n00b Joined: 06 Sep 2004 Posts: 58

You should take a look at LUFS and other user-mode based filesystems.
Link to Lufs:http://lufs.sourceforge.net/lufs/

Basically the idea is that they provide in the kernel drivers, and execute whatever you want when the file operations are called.

Be careful though, as improperly coding these may be a security risk.

Geoff Russell · n00b Joined: 28 Apr 2004 Posts: 16

Thanks, lufs looks like a definite possibility.

Also using the amd automounter looks a little more ugly but
possible since you can configure arbitrary co

The fallback solution is to keep track of all updates to
the necessary tables and refresh the xml when appropriate.

alv · n00b Joined: 06 Sep 2004 Posts: 58

Actually it seems that lufs is a bit dated, and FUSE is supposedly the new thing.

http://fuse.sourceforge.net/