Date: Sun, 26 Jun 2016 16:34:11 +0200 From: Polytropon <freebsd@edvax.de> To: =?UTF-8?B?RGFuacOrbA==?= de Kok <me@danieldk.eu> Cc: freebsd-questions@freebsd.org Subject: Re: grep and anchoring Message-ID: <20160626163411.d05f863e.freebsd@edvax.de> In-Reply-To: <20232C89-B821-41EC-9188-C2A19C679BD8@danieldk.eu> References: <20232C89-B821-41EC-9188-C2A19C679BD8@danieldk.eu>
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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. 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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