Re: lowercase letters for binaries

[Andreas Schwab]

Benno Schulenberg <address@hidden> writes:

> Hmm...  I'm not sure that backreferences are working correctly.  
> Shouldn't
>
>   echo "cbaa" | egrep '(aa)cb|cb\1'
>
> give output?

Since (aa) does not match anything, what should \1 match?  Note that a
back-reference does not repeat the matching of the referenced
subexpression, but only matches the exact string that was previously
matched.

>  This does:
>
>   echo "cbaa" | egrep '(aa)cb|cb(a)\2'

Note that POSIX does not allow back-references in EREs, only in BREs which
don't have alternation.

Andreas.

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Andreas Schwab, SuSE Labs, address@hidden
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