Date: Sun, 26 Jun 2016 16:44:44 +0200 From: =?utf-8?Q?Dani=C3=ABl_de_Kok?= <me@danieldk.eu> To: Polytropon <freebsd@edvax.de> Cc: freebsd-questions@freebsd.org Subject: Re: grep and anchoring Message-ID: <362EE01F-4B49-4ADB-A3A6-43F852FFF87F@danieldk.eu> 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:
> Or is this just an "enrichment" your MUA added? :-)
Yes, Mac’s Mail.app likes to replace these. I didn’t use an ellipsis in the actual expression ;), just four dots.
> % echo "1234 1234 1234" | egrep -o '^....'
> 1234
> 123
> 4 12
[...]
> 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).
Note the anchoring (^), the pattern should only match any four characters at the beginning of the line, so the expected output is ‘1234’ and nothing more. ‘ 123' and '4 12' are not at the beginning of the line and should consequently not be printed to stdout.
For comparison, the output of a recent GNU grep:
—
% echo "1234 1234 1234" | grep -o '^....'
1234
—
With kind regards,
Daniël de Kok
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