GNU bug report logs - #41004
Documentation:enhancement - search for hexvalue

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Message #8 received at 41004 <at> debbugs.gnu.org (full text, mbox):

From: Jim Meyering <jim <at> meyering.net>
To: Radisson97 <at> web.de
Cc: 41004 <at> debbugs.gnu.org
Subject: Re: bug#41004: Documentation:enhancement - search for hexvalue
Date: Sun, 3 May 2020 12:25:04 -0700

On Fri, May 1, 2020 at 10:07 AM <Radisson97 <at> web.de> wrote:
> Hi,
> i had the problem of searching for a non-printable character in a long
> list of strings. I found nothing the documentation and but several discussion
> how to do that where either complicated or did not fit for my case, maybe i
> was unlucky, ntl i found a simple solution that should be mentioned in the
> documentation.
>
> problem: grep for a character where only the hexcode in known.
>
> solution:        use $'\xNN'
>                      then shell expands this to the required code
>
> example:       printf "A\nB\nC\n" | grep $'\x41'
>
> note: that uses only printable characters, it works also with anything else
>          except \0 (i guess).
>
> i found that solution nice, it did no require any flags etc, for my problem it
> worked like a charm.
> (i am not member of the list please reply directly to this address) .

Thank you for the suggestion. Another approach is to use grep's -P option:

$ printf '%s\n' A B C| grep -P '\x41'
A

If you'd like to add an example to the documentation, please send a
patch, but I'm not sure how much of PCRE syntax we want to document in
grep's own manual.

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