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Re: Bogus assumption prevents d2u/u2d/conv/etal working on mixed files
- From: Igor Pechtchanski <pechtcha at cs dot nyu dot edu>
- To: fergus at bonhard dot uklinux dot net
- Cc: cygwin at cygwin dot com
- Date: Tue, 6 Apr 2004 15:19:46 -0400 (EDT)
- Subject: Re: Bogus assumption prevents d2u/u2d/conv/etal working on mixed files
- Reply-to: cygwin at cygwin dot com
On Tue, 6 Apr 2004, fergus wrote:
> >> GNU grep detects binary files by looking for a '\0' byte.
>
> I know this is not strictly Cygwin-specific but it _is_ generated by the
> preceding relevant recent comment in a busy thread:
>
> Please can you tell me how to grep for an ASCII 00 (and for that matter
> anything from ASCII 1B to 1F, and 7F to FF)?
>
> (Or, I suppose in general for any of 00-FF though there's a "^A - ^Z" chunk
> at the beginning and a alphanumeric chunk in the middle, that are easily
> found by direct means.)
>
> Fergus
For anything but '\0', grep has no problem matching binary characters, so
you can use something like
grep -a "`echo -ne "\01"`"
or
grep -a "^V^A" (from the command line)
to match lines with ^A in them. Unfortunately, grep uses '\0' as a string
terminator, so the above trick won't work with '\0'. The best you can
hope to do with grep (or, for that matter, sed) is use "[[:cntrl:]]".
You *can*, however, use perl for this:
perl -ne 'print if /\0/'
HTH,
Igor
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