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From: John (I've got some bad news for you, sunshine) Mackin <john@vetsci.su.oz.au>
Date: Sat, 1 Feb 1992 12:02:44 -0600
To: The rc Mailing List <rc@archone.tamu.edu>
Subject: Re: Match operator puzzlement
In-Reply-To: <92Feb1.114911cst.18888@archone.tamu.edu>
Message-ID: <199202020502.20639.rc.badig@vetsci.su.oz.au>
X-Face: 39seV7n\`#asqOFdx#oj/Uz*lseO_1n9n7rQS;~ve\e`&Z},nU1+>0X^>mg&M.^X$[ez>{F
 k5[Ah<7xBWF<un6={nlL7Om5<0UsuHKjCxs)C$`DP.N'-LLb8=8)"a@d2bG-f7qD2AJ#UZ>-@-ru?&
 @4K4-b`ydd^`(n%Z{

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.