dovecot - Oct 2020 - Understanding matches in sieve

RFC 5229 gives the following example:

if address :matches ["To", "Cc"] ["coyote@**.com",
              "wile@**.com"] {
          # ${0} is the matching address
          # ${1} is always the empty string
          # ${2} is part of the domain name ("ACME.Example")
          fileinto "INBOX.business.${2}"; stop;

And I do not understand why ${1} is always the empty string.

In this example, ${1} is the part before the < so using ${2} makes sense.

 if header :matches "List-ID" "*<*@*" {
          fileinto "INBOX.lists.${2}"; stop;
      }

I am laso not sure why the first example used **.com instead of *.com (or is
that the reason $1 doesn't contain anything because it is the first * of
**?).

If so, my familiarity with the bash syntax for ** may have been my undoing.

If I had

# Given to kremels at kreme.com
if address :matches ["To", "Cc"] ["*@*.*"]
   # ${1} would contain "kremels"
   # ${2} would contain "kreme"
   # ${3} would contain "com"

Yes?


-- 
"Are you pondering what I'm pondering?"
"Sure, Brain, but how are we going to find chaps our size?"

On 10/21/20 11:15 AM, @lbutlr wrote:
> RFC 5229 gives the following example:
> 
> if address :matches ["To", "Cc"]
["coyote@**.com",
>               "wile@**.com"] {
>           # ${0} is the matching address
>           # ${1} is always the empty string
>           # ${2} is part of the domain name ("ACME.Example")
>           fileinto "INBOX.business.${2}"; stop;
> 
> And I do not understand why ${1} is always the empty string.
This is because of the text above that: "The wildcards match as little
as possible (non-greedy matching)."

This example has two wildcards in a row (""**" doesn't mean
anything
special beyond that) -- and because the first "*" matches as little as
possible, it matches nothing (the empty string). The second "*"
matches
everything between "@" and ".com".

The same thing happens with real regexps:

 #!/usr/bin/perl
 $x = 'coyote at ACME.Example.COM';
 $x =~ /coyote\@(.*?)(.*?)\.COM/;
 printf '$1 is "%s"; $2 is "%s"', $1, $2;

This will print:

 $1 is ""; $2 is "ACME.Example"

> I am laso not sure why the first example used **.com instead of *.com (or
is that the reason $1 doesn't contain anything because it is the first * of
**?).
Yes. The example is confusing because it makes it look like "**" is
some
magic thing you might want to use. It's not.

-- 
Robert L Mathews, Tiger Technologies, http://www.tigertech.net/

On 21 Oct 2020, at 18:04, Robert L Mathews <lists at tigertech.com>
wrote:
> On 10/21/20 11:15 AM, @lbutlr wrote:
>> I am laso not sure why the first example used **.com instead of *.com
(or is that the reason $1 doesn't contain anything because it is the first *
of **?).
> Yes. The example is confusing because it makes it look like "**"
is some
> magic thing you might want to use. It's not.
Thank you for confirming that. It's a really bad example.

-- 
"Are you pondering what I'm pondering?"
"Yes, but why does the chicken cross the road, huh, if not for love?
	I do not know."