[TriLUG] Negative search in Vi
ctalkobt at gmail.com
Sat Apr 12 20:07:01 EDT 2008
Ack, you're right - As I said I didn't check it before posting - however
after reading the vi :help on pattern matching and trying umpteen different
ways I've found
1) Lots of confusing regexp stuff. :-)
Something similar to /\(.|..|[^d][^o][^g].*\)/\@! might work but I can't
get the syntax right... I may be misunderstanding the use of the \@! syntax.
To get back to the original issue -
Try this (I did test these... )
- Replace "dog" with a symbol that's not used in your file, eg : @
- Search for all lines that do not have an @ : /^[^@]*$
- After you're finished, replace @ with dog again.
- Craig Taylor
On Sat, Apr 12, 2008 at 7:09 PM, Michael Tharp <gxti at partiallystapled.com>
> Craig Taylor wrote:
> > Negate your regular expression search, eg: for lines that don't have
> > use :
> > /^.*[^d][^o][^g].*$
> > disclaimer: this has not been tested - I believe it should work 'tho)
> > - Craig Taylor
> >>> foo = re.compile('^.*([^d][^o][^g]).*$')
> >>> sample = 'the quick brown fox jumped over the lazy dog'
> >>> bool(foo.search(sample))
> >>> foo.search(sample).groups()
> (' do',)
> The problem here is this:
> 1. The first ".*" gobbles up everything up to "dog"
> 2. [^d][^o][^g] doesn't match "dog", so it backtracks by one character
> to " do"
> 3. It matches, since " do" != "dog"
> 4. The second ".*" gobbles up the remainder of the string
> Doing negative matches is surprisingly difficult and I honestly can't
> say I know of a way to do this with just a regular expression, either.
> Aaron's suggestion of deleting all matching lines and stepping through
> the remainder is probably the most plausible. Honestly, if this is
> possible, it has to be a feature of vim itself, not some regex trickery.
> As I wrote this, Kevin posted a recommendation for lookahead/behind
> assertions, but remember that those only work if you have something to
> anchor them to! You can't say "match anything but dog" with an assertion
> unless you have something that you *do* match first, and then say "match
> if it is not followed by dog". In Kevin's example, the anchor is the end
> of the string, but this is insufficient for simply checking whether
> something is not present if it could be anywhere in the middle.
> -- m. tharp
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