Date: Sat, 2 Nov 2019 14:57:14 -0400 From: Kurt Hackenberg <kh@panix.com> To: freebsd-questions@freebsd.org Subject: Re: grep for ascii nul Message-ID: <7775e7f8-89ba-d057-67d3-cdcb92d2bbb4@panix.com> In-Reply-To: <20191102064505.GA98558@admin.sibptus.ru> References: <20191101092716.GA67658@admin.sibptus.ru> <63808.1572638827@segfault.tristatelogic.com> <20191102064505.GA98558@admin.sibptus.ru>
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On 2019-11-02 02:45, Victor Sudakov wrote:
> I'm a big fan of awk, awk is in the base system and should be able to do
> it, right?
>
> $ hd trees.txt
> 00000000 66 69 72 0a 6f 61 6b 0a 63 65 64 00 61 72 0a 62 |fir.oak.ced.ar.b|
> 00000010 69 72 63 68 0a 70 61 6c 6d 0a |irch.palm.|
> 0000001a
> $
>
> Note the ascii null embedded in the word "cedar"
>
> $ awk '/\x66\x69/{print $0}' trees.txt
> fir
>
> So far so good. But with the ascii nul it behaves in an unexpected way:
>
> $ awk '/\x00/{print $0}' trees.txt
> fir
> oak
> ced
> birch
> palm
> $
Looks like it has the same problem that I guess grep does: it takes that
NUL as the end of a C string, so the regexp becomes a null string (zero
length), which matches everything.
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