Re: Match operator puzzlement

[John (I've got some bad news for you, sunshine) Mackin <john@vetsci.su.oz.au>]

Byron gives us:

	sed -e 's/\([^[*?]\)/''\1''/g' -e 's/''''//g'

Damn good thinking.  Top notch in fact.  It is possible to make
this work for input containing ', but in an indirect manner.  I think you
have to be indirect since I don't think a grep-style RE can do that.
In practice, there is a neat enough solution: assume that newline
doesn't appear in the input string and initially map ' into newline,
then map that back into '' on output.  As long as the character you
pick doesn't occur in the input it's fine.  Yes, it's a kludge, but
I would be very surprised to find people with real applications for
command-line patterns containing newline.

I'm not prepared to say that it can't be done with an egrep-style (full)
RE but I can't see a solution.  If anyone has one please mail it to the list.

Extending Byron's sed produces this (with $nl being a newline, as usual):

	sed	-e 's/''/\' ^ $nl ^ '/g'	\
		-e 's/\([^[*?]\)/''\1''/g'	\
		-e 's/''''//g'			\
		-e 's/\n/''''/g'

OK,
John.