On Tue, 13 Jun 2006, Edward Wong wrote:
> It follows the general form of a negative line search for embedded
> <search>:
>
> /^\%(.*[<limit0>.*]<search>[.*<limit1>]\)[EMAIL PROTECTED]
>
> For example, to match a line that contains "foo" but does not contain
> "bar" between "big" and "tummy":
>
> /\%(.*big.*bar.*tummy\)[EMAIL PROTECTED]
Learn a lot more about regexp from this post. Thanks!
Sorry, I missed the ^ anchor:
/^\%(.*big.*bar.*tummy\)[EMAIL PROTECTED]
Just a question, why it is necessary to have the ^ anchor? Isn't .*
already includes the characters start from the beginning of the line?
[snip]
No, .* does not start from the beginning of the line. If nothing is
specified before it in a search expression, it matches everywhere.
To give you a better picture, given the line:
123big bar tummy45
when you do a search
/.*
what it actually does is try to match .* at 1, 2, 3, b, i, etc. But as
soon as it starts with 1, the whole line gets matched because of the *
quantifier (greedy zero or more). This may give you the false impression
that it began from the beginning of the line.
Likewise, doing
/.
shows that the search expression is done for every character. The regex
engine searches, and when it finds a match, it increments the pointer
one character after the end of the current match and searches again.
Generally, it's a good idea to place something unique before the
[EMAIL PROTECTED] expression's atom, because there are a lot places where an
expression does _not_ match. And since we're dealing with line matching
here, the best unique identifier to use is the start of line anchor ^.
It's a one-character regex, a zero-width match, unique (for the current
line), intuitive (for line matching), and always exists.
So if you perform
/\%(.*big.*bar.*tummy\)[EMAIL PROTECTED]
(without the ^ anchor)
on the line mentioned above, the regex search would look for the every
occurence where .*big.*bar.*tummy does _not_ match and try to match the
trailing .* at those locations (note the plurality).
The first occurence where the [EMAIL PROTECTED] atom does not match is at "i".
Then .*
would match:
end of match
V
ig bar tummy45
^
beginning of match
See
:help /[EMAIL PROTECTED]
:help /^
:help search-pattern
HTH :)
--
Gerald
