RE: How to get a list of all available PVs

[<michael.abbott@diamond.ac.uk>]

From: Carlos Pascual [mailto:cpascual@cells.es]
> On Mon 17 December 2012 12:38:10 michael.abbott@diamond.ac.uk wrote:
> > This monitoring tool sits between the machine network carrying PV
> > traffic and our internal database, which itself provides a web interface.
> > Each time a CA_PROTO_SEARCH message is seen for a new PV I add it to an
> > internal table and create my own discovery message to locate the serving
> > IOC; once found, an update is sent to our database and the PV is
> > periodically refreshed.
 
> Very interesting. A similar system but monitoring for
> CA_PROTO_RSRV_IS_UP instead of CA_PROTO_SEARCH would
> work for me provided that then I can get a list of PVs
> from a given IOC.

Don't believe such a mechanism exists at present, but see below.


> > > And if so, is there a way of interrogating a given IOC for its PVs?
> >
> > In principle such a mechanism could be created, but I don't believe
> > it exists at present.
> 
> What do you mean by "could be created"? Do you mean that Epics could
> provide some API to this effect in the future?... Or that a way could
> be found to do it with existing APIs? ... or something else?

One or the other, I've not looked to see what would be involved (well, I have now...).  I'd start by thinking of providing a simple socket interface which walks the database, or maybe just returns the results of dbgrep.

Actually, a glance at the implementation of dbgrep (src/db/dbTest.c) suggests that the existing code is close to what you need, but needs a tweak (rather than calling puts you'll want more control over where the strings go), but it looks to me as if all the functions called by dbgrep are exported by epics, so writing what you need should be exceptionally easy: just grab a copy of dbgrep, give it a file handle output, replace puts, wrap a socket interface around it, launch it as part of your IOC startup scripts.

If it were me, I'd dedicate a socket, read one line from the input, treat it as input to the modified dbgrep, send the results in response, close the socket.  Then `echo \* | nc $IOC $PORT` would give you a list of all PVs exported by the IOC.

Of course, you'll need to add this code to every IOC...

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