Обсуждение: problem with regexp (cant quote +)

postgres 7.3.2:

I wonder why the following expression fails. I came to this wondering why I
could not search for + using the '~'-operator.

select 'ok' where 'H+H'~'H\+H';

thnx,
peter


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On Sat, Jul 05, 2003 at 04:46:47PM +0200, peter pilsl wrote:
>
> I wonder why the following expression fails. I came to this wondering why I
> could not search for + using the '~'-operator.
>
> select 'ok' where 'H+H'~'H\+H';

You need to double the backslash, because the first one is going away at
parse time (you need a literal \ for the regex).

alvh=> select 'ok' where 'H+H' ~ 'H\\+H';
 ?column?
----------
 ok
(1 row)

Yeah, annoying, but easily understood.  Other tools behave the same:
$ echo 'H+H' | egrep H+H
$ echo 'H+H' | egrep H\+H
$ echo 'H+H' | egrep H\\+H
H+H

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