Re: [Grep-devel] [bug-gawk] GNU grep, awk, sed: support \u and \U for unicode

[Paul Eggert]

Assaf Gordon wrote:
> Currently, escape sequences are parsed and converted before
> being sent to re/dfa.
> Thus, '[\u0041]' is equivalent to '[A]'

POSIX requires [\u0041] to be equivalent to [u0041\], that is, it matches any of 
the characters '\', 'u', '0', '4', and '1'. This is true for grep, sed, and most 
other utilities that use regular expressions. (awk is an exception.) So except 
for awk, we can't simply translate \u escapes everywhere. At best we could 
translate them only if not POSIXLY_CORRECT.

On another topic, if we can't implement \N escapes in general then I wouldn't 
bother with implementing only \N{U+nnnn}.