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Re: GNU grep 2.5.1
From: |
Claudio Fontana |
Subject: |
Re: GNU grep 2.5.1 |
Date: |
Fri, 1 Apr 2005 22:56:41 +0200 (CEST) |
Hello,
the correct place to speak about supposed grep bugs is
now address@hidden .
By the way, I think that Marvin is trying to avoid
using od and going directly for the bytes when he
says:
> I have been doing
>
> od -x bigDataFile | grep -c "aa55 0000 0490"
>
> which gives me the answer 560912 when a file has not
> been
> corrupted. This is fine but quite slow.
>
> Today I decided that
>
> grep -c "\xaa\x55\x00\x00\x04\x90" bigDataFile
>
> should be faster.
The main problem is that the \xnn syntax is not a
posix regex, but a perl regex.
There is another (byte ordering) problem in the fact
that od -x shows bytes in pairs, interpreting them as
short integers.
I think the original poster would solve his problem
by:
1) using
$ od -t x1 BigDataFile
to extract the correct byte by byte sequence he wants
to use as validation
2) replacing
grep -c "\xNN\xNN\xNN"
with
grep -P -c '\xNN\xNN\xNN'
This being said, there are lots of better solutions to
the 'validation' problem that do not involve grep.
Hope this helps.
Claudio
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- GNU grep 2.5.1, Marvin Hile, 2005/04/01
- Re: GNU grep 2.5.1,
Claudio Fontana <=