Re: Quickie - Regexp for a string not at the beginning of the line

[Ed Morton <mortonspam@gmail.com>]

On 10/25/2012 11:45 PM, Rivka Miller wrote:
> Thanks everyone, esp this gentleman.
>
> The solution that worked best for me is just to use a DOT before the
> string as the one at the beginning of the line did not have any char
> before it.

That's fine but do you understand that that is not an RE that matches on 
"$hello$ not at the start of a line", it's an RE that matches on "<any 
char>$hello$ anywhere in the line"? There's a difference - if you use a tool 
that prints the text that matches an RE then the output if the first RE existed 
would be "$hello$" while the output for the second RE would be "X$hello$" or 
"Y$hello$" or....

In some tools you can use /(.)$hello$/ or similar to ignore the first part of 
the RE "(.)" and just print the second "$hello", but that ability and it's 
syntax is tool-specific, you still can't say "here's an RE that does this", 
you've got to say "here's how to find this text using tool <whatever>".

    Ed.

> I guess, this requires the ability to ignore the CARAT as the beginning of the line.
>
> I am a satisfied custormer. No need for returns. :)
>
> On Oct 25, 7:11 pm, Ben Bacarisse <ben.use...@bsb.me.uk> wrote:
>> Rivka Miller <rivkaumil...@gmail.com> writes:
>>> On Oct 25, 2:27 pm, Danny <dann90...@gmail.com> wrote:
>>>> Why you just don't give us the string/input, say a line or two, and
>>>> what you want off of it, so we can tell better what to suggest
>>
>>> no one has really helped yet.
>>
>> Really?  I was going to reply but then I saw Janis had given you the
>> answer.  If it's not the answer, you should just reply saying what it is
>> that's wrong with it.
>>
>>> I want to search and modify.
>>
>> Ah.  That was missing from the original post.  You can't expect people
>> to help with questions that weren't asked!  To replace you will usually
>> have to capture the single preceding character.  E.g. in sed:
>>
>>    sed -e 's/\(.\)$hello\$/\1XXX/'
>>
>> but some RE engines (Perl's, for example) allow you specify zero-width
>> assertions.  You could, in Perl, write
>>
>>    s/(?<=.)\$hello\$/XXX/
>>
>> without having to capture whatever preceded the target string.  But
>> since Perl also has negative zero-width look-behind you can code your
>> request even more directly:
>>
>>    s/(?<!^)\$hello\$/XXX/
>>
>>> I dont wanna be tied to a specific language etc so I just want a
>>> regexp and as many versions as possible. Maybe I should try in emacs
>>> and so I am now posting to emacs groups also, although javascript has
>>> rich set of regexp facilities.
>>
>> You can't always have a universal solution because different PE
>> implementations have different syntax and semantics, but you should be
>> able to translate Janis's solution of matching *something* before your
>> target into every RE implementation around.
>>
>>> examples
>>
>>> $hello$ should not be selected but
>>> not hello but all of the $hello$ and $hello$ ... $hello$ each one
>>> selected
>>
>> I have taken your $s to be literal.  That's not 100 obvious since $ is a
>> common (universal?) RE meta-character.
>>
>> <snip>
>> --
>> Ben.
>