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Re: wildcard authz docs question

From: Doug Robinson <doug.robinson_at_wandisco.com>
Date: Tue, 28 Mar 2017 09:05:53 -0400

Daniel:

Sorry for the delay - I missed the post.

And, I'm going to recant my original conclusion - my apologies for not
treating this with sufficient vigor the 1st time around.

Wow - it's been a long time since I played with zsh. Yep, I see the
reference to "‘***/*’ is equivalent to ‘*(*/)#*’". So, playing with this,
the zsh man page is a bit loose with the term "file" where they are really
talking about a "directory entry":

# ls -dl **/foo
drwxr-xr-x 2 root root 4096 Mar 28 14:32 a/b/c/foo
# ls -dl **/bar
-rw-r--r-- 1 root root 0 Mar 28 14:32 a/b/c/bar
# ls -dl **/baz
lrwxrwxrwx 1 root root 10 Mar 28 14:36 a/b/c/baz -> a/b/c/biff

That said, in discussions I've had I think about the SVN regex "**"
differently than the zsh construct. The way that I interpret "/**" is
"everything below and including slash" - so "**" is the moral equivalent of
Perl's ".*" wildcard. It need not be followed by any terminal pattern to
match anything - since it matches them all. If it was followed by
something then that something would be required.

So let me break the 3 patterns down:

/*/*/** This requires 2 directories. It will match all directories 2
levels down - and then everything in all of the rest of those trees however
deep. It should not, however, match a file or symlink in a directory, e.g.
"/dirA/fileB". Whereas it will match "/dirA/dirB" along with
"/dirA/dirB/fileC", etc.

/*/**/* This requires 1 directory and then something else. It will match
"/dirA/fileB" or "/dirA/symlinkX" since "/**" can simply go to nothing. Or
perhaps a different way to look at it is that "/**" can match "/" which, in
its simplest will mean "/*/**/*" becomes "/*//*" and given that multiple
'/' always collapse to a single '/' in "path arithmetic" becomes "/*/*" for
its shortest match.

/**/*/* This requires 1 directory and then something else. Pretty much
the same as the prior example and for the same reasons.

Is this more along the lines of what you were thinking?

Thank you.

Doug

On Tue, Mar 21, 2017 at 12:36 PM, Daniel Shahaf <d.s_at_daniel.shahaf.name>
wrote:

> Doug Robinson wrote on Tue, Mar 21, 2017 at 11:40:50 -0400:
> > Daniel:
> >
> > The shell's all treat ** as * and require that it match something. So
> > "mkdir -p foo/bar/baz" would match.
> >
> > No command shell that I know of (sh,bash,zsh,tcsh,csh,ksh) has a
> > moral equivalent to "zero or more path components". Perl, python,
> > et. al. do.
>
> zsh interprets ** as meaning "zero or more path components" when it's
> followed by a slash:
>
> % mkdir -p foo/bar
> % echo */**
> foo/bar
> % echo */**/
> foo/ foo/bar/
>
> I looked up the Python and Perl equivalents, but the Python one has
> a bug (the pattern '*/*/**' finds 'trunk/iota/' — with a trailing
> slash — even if trunk/iota is a file) and I found no Perl equivalent in
> its stdlib's File::Glob, so I couldn't compare against either of them.
>
> > I would expect "/*/**/*", "/**/*/*" and "/*/*/**" to all match exactly
> the
> > same sets of components.
>
> Then our expectations are different as to what */*/** should mean. Can
> you give an example of a tool where ./*/*/** matches ./trunk/iota when
> iota is a file (not a directory)? As I said in my previous mail,
> neither vim nor zsh — which, to clarify, both support a ** recursion
> operaetor — match ./trunk/iota in that situation.
>
> Thanks for jumping in.
>
> Cheers,
>
> Daniel
>
>
> > Cheers,
> >
> > Doug
> >
> > On Wed, Mar 15, 2017 at 5:55 AM, Daniel Shahaf <d.s_at_daniel.shahaf.name>
> > wrote:
> >
> > > From the 1.10 draft release notes:
> > >
> > > > All wildcards apply to full path segments only, i.e. * never matches
> > > > /, except for the case where /**/ matches zero or more path segments.
> > > > For example, /*/**/* will match any path which contains at least
> > > > 2 segments and is equivalent to /**/*/* as well as /*/*/**.
> > >
> > > Are «/*/**/*» «/**/*/*» «/*/*/**» really equivalent? I would have
> > > expected the first two to match any node except / and /'s immediate
> > > children, but I wouldn't expect the third form to match /trunk/iota
> > > where iota is a file, since the pattern has a trailing slash after the
> > > non-optional second component.
> > >
> > > Testing this in
> > > cd $(mktemp -d)
> > > mkdir -p foo/bar
> > > , I see that neither vim nor zsh finds any matches for */*/**, meaning
> > > they don't interpret ** as "zero or more" path components in this
> > > pattern. I suppose they only treat ** in this way when it appears with
> > > slashes immediately before and after it.
> > >
> > > Cheers,
> > >
> > > Daniel
>

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Received on 2017-03-28 15:06:04 CEST

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