Re: meaning of backslash single-quote?

[Paolo Bonzini]

On 07/25/2011 12:30 AM, Bruno Haible wrote:
> Hi,
>
> GNU grep (I tested versions 2.5, 2.7, 2.9) appears to assign a meaning to
> the backslash single-quote character sequence in the argument that ought to
> be a Basic Regular Expression.
>
> $ grep --version
> grep (GNU grep) 2.9
> ...
> $ echo ' abc" ' | grep "\"\\'"
> $ echo ' abc"' | grep "\"\\'"
>   abc"

It's end-of-buffer, together with \` for beginning of buffer.  It makes 
a difference from ^ and $ when using -z, IIRC.

> As a quality of implementation issue, I would prefer to get an error message
> for such an undefined BRE.

I don't think this is a good idea.  There are certainly a lot of scripts 
in the wild using \" (due to confusion about quoting) or \- (due to lack 
of knowledge of "--" command-line behavior).

Paolo