[File] A few questions regarding the actual semantic of "magic" rules

[Christos Zoulas]

> On Jun 3, 2024, at 5:30 AM, Marco Antoniotti <marcoxa at gmail.com> wrote:
> 
> Hi
> 
> 
> 
> Thank you for supporting this tool for so many years.
> 
> 
> 
> I have a few questions regarding the actual semantics of magic(5) rules.
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> Let me call "group" a set of tests starting at a 0 level test.
> 
> My understanding is that each group is checked separately and that, once one of them "succeeds" then the result is printed out and that's it.  I am saying this otherwise the "pdf" specification should print out two equal lines on a vanilla PDF file.  Is that correct?
Yes, unless -k is specified the first "group" matched that prints something "succeeds".
> I understood that "name" and "use" rules can span magic(5) boundaries.  Is that correct?

That is correct. The program looks for a named rule in all the rules it has loaded so far.
> When I use a "use" clause, what is the state of the position in the file (buffer) after its invocation?  Whether it is successful or not?
IIRC should be restored to what it was before the USE call.
> Can I "use" a "name" that then uses another "name" etc.  It does not appear to be the case on Mac OS right now.

Should be able to. Can you give an example that does not work?

> I also believe I found a few problems with some of the magic(5) files; I will post them soon.
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> That's it for now.
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> 
> Thanks
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> 
> Marco
> 
> 
> PS  Yes, I am parsing the magic(5) files.  Don't ask!  It's a rabbit hole.
> 

The program has organically grown for a very long time, so there are many weird corner cases.

christos

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