How can I "inverse match" with regex?

Question

(?!Andrea).{6}

Assuming your regexp engine supports negative lookaheads...

...or maybe you'd prefer to use [A-Za-z]{6} in place of .{6}

Note that lookaheads and lookbehinds are generally not the right way to "inverse" a regular expression match. Regexps aren't really set up for doing negative matching; they leave that to whatever language you are using them with.

For Python/Java,

^(.(?!(some text)))*$

http://www.lisnichenko.com/articles/javapython-inverse-regex.html

In PCRE and similar variants, you can actually create a regex that matches any line not containing a value:

^(?:(?!Andrea).)*$

This is called a tempered greedy token. The downside is that it doesn't perform well.

The capabilities and syntax of the regex implementation matter.

You could use look-ahead. Using Python as an example,

import re

not_andrea = re.compile('(?!Andrea)\w{6}', re.IGNORECASE)

To break that down:

(?!Andrea) means 'match if the next 6 characters are not "Andrea"'; if so then

\w means a "word character" - alphanumeric characters. This is equivalent to the class [a-zA-Z0-9_]

\w{6} means exactly six word characters.

re.IGNORECASE means that you will exclude "Andrea", "andrea", "ANDREA" ...

Another way is to use your program logic - use all lines not matching Andrea and put them through a second regex to check for six characters. Or first check for at least six word characters, and then check that it does not match Andrea.

Negative lookahead assertion

(?!Andrea)

This is not exactly an inverted match, but it's the best you can directly do with regex. Not all platforms support them though.

If you want to do this in RegexBuddy, there are two ways to get a list of all lines not matching a regex.

On the toolbar on the Test panel, set the test scope to "Line by line". When you do that, an item List All Lines without Matches will appear under the List All button on the same toolbar. (If you don't see the List All button, click the Match button in the main toolbar.)

On the GREP panel, you can turn on the "line-based" and the "invert results" checkboxes to get a list of non-matching lines in the files you're grepping through.