Date: Sun, 26 Jun 2016 16:41:47 +0200 From: Eir Nym <eirnym@gmail.com> To: Polytropon <freebsd@edvax.de> Cc: =?utf-8?Q?Dani=C3=ABl_de_Kok?= <me@danieldk.eu>, freebsd-questions@freebsd.org Subject: Re: grep and anchoring Message-ID: <C23FABAB-1F4F-4654-917C-1E5A50E0E257@gmail.com> In-Reply-To: <20160626163411.d05f863e.freebsd@edvax.de> References: <20232C89-B821-41EC-9188-C2A19C679BD8@danieldk.eu> <20160626163411.d05f863e.freebsd@edvax.de>
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> On 26 Jun 2016, at 16:34, Polytropon <freebsd@edvax.de> wrote:
>
> On Sun, 26 Jun 2016 15:10:57 +0200, Daniël de Kok wrote:
>> Dear all,
>>
>> After a BSD hiatus of many years, I am tinkering with FreeBSD again.
>> I’ve run into some strange issue with grep and beginning of line (^)
>> anchoring:
>>
>> —
>> % echo "1234 1234 1234" | egrep -o '^….'
>> 1234
>> 123
>> 4 12
>> % echo "123412341234" | egrep -o '^....'
>> 1234
>> 1234
>> 1234
>> —
>>
>> Any idea what is going on here?
>
> I think what you see here is a typical "UTF-8 fsck-up".
> The first search pattern contains a an ellipsis ("…",
> 2 bytes long, representing 3 characters), and a single
> dot (".", one byte long, 1 character); the second pattern
> contains four dots (4 x ".", 1 byte long, 1 character).
> Of course grep interprets "…" and "..." differently.
> In my mailer, I can see the difference clearly as the
> ellipsis … is displayed in monospace font as a _one_
> character wide symbol on the screen.
>
I think this was automatic spell correction and he mentioned 4 dot symbols (.), not a ‘…' and ‘.’
> Or is this just an "enrichment" your MUA added? :-)
>
> I'm quite sure you run into similar problems when you
> include ligatures (like st, ft, ffi, ck or the like)
> or one of the many different hyphend and spaces in a
> search pattern. :-)
>
> Otherwise, your example seems to show the expected
> behaviour.
>
> % echo "1234 1234 1234" | egrep -o '^....'
> 1234
> 123
> 4 12
>
> % echo "123412341234" | egrep -o '^....'
> 1234
> 1234
> 1234
>
> First 4-character pattern is "1234", next is " 123",
> and last is "4 12" (each 4 characters wide, as the
> space character " " is also "any character" that matches
> the . pattern). In the second example, the groups match
> 4 characters each ("1234" x 3).
>
> What different results did you expect? Or am I misinterpreting
> your question?
>
>
> --
> Polytropon
> Magdeburg, Germany
> Happy FreeBSD user since 4.0
> Andra moi ennepe, Mousa, ...
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