Experimental Physics and
Industrial Control System

Andrew Johnson <[email protected]> · Thu, 8 Sep 2016 13:35:43 -0500

On 09/08/2016 12:54 PM, Konrad, Martin wrote:
>>>>> Turns out EPICS won't load a record whose name starts with '.'
> '.' is used as a separator between the record name and the field name. I
> guess record names of length 0 are not allowed. Thus a valid PV name can
> never start with a '.' and we should remove it from the list of
> characters in my patch. I updated my patch accordingly.

Agreed.

> I'm still a bit confused about the fact that 6.4.11.2 allows '+' as part
> of the record name. However '+' seems not to be allowed in PV names.

The '+' character should appear in the bareword character list given in
section 6.3.2 (compare with the definition of bareword given in
dbStaticLib/dbLex.l for proof). It does appear in the list given at
6.4.11.2 so it is allowed in a record name.

> Isn't this calling for trouble? Can someone please shine some light on this?

The wording in 6.3.2 is evidently a source of confusion, that section is
really only documenting where you need quotes in your .db files. I'll
add the '+' and change the paragraph afterwards to this:

    These are all legal characters for process variable names, although
    \verb|.| is not allowed in a record name since it separates the
    record from the field name in a PV name. Thus in many cases quotes
    are not needed around record or field names in database files. Any
    string containing a macro does need to be quoted though.

> Regarding '_', '-', ':', '[', ']', '<', '>', and ';' I don't see any
> reason why they shouldn't be allowed at the beginning of a record/PV
> name. These characters might not be my first choice to start a record
> name with but they seem to be allowed and in my mind should be handled
> by Autosave like alpha-numeric characters.

I agree.

- Andrew

-- 
Arguing for surveillance because you have nothing to hide is no
different than making the claim, "I don't care about freedom of
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Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System