[TriLUG] regex: match lines NOT containing X
alexeyt at freeshell.org
Wed Feb 22 10:26:14 EST 2012
On Wed, 22 Feb 2012, Kevin Hunter wrote:
> Hullo List,
> An actual technical question here: Is there a way to match an entire line
> such that the entire line does *not* contain a sequence of characters?
> Example input containing three lines:
> If two heads are better than one,
> are two keyboards better than one?
> Would you say the same if it were two hydra heads?
> My criteria is very specific: I want lines that do *not* contain 'heads'. My
> first thought was to use an assertion:
> However, this naive implementation matches both lines 2 and 3. I've needed
> this construct more than a few times, so I'm almost sure it exists; I just
> don't know the right Google terms, apparently. On the other hand, I could
> accept that this may not be possible in a single step regex.
> Any ideas?
If you can't invert the whole regex (as in grep -v or !~ in perl), you can
This technique quickly becomes unwieldly as the size of the string that
must not match grows...
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