如果文本包含某些字符，则正则表达式不匹配

Question

I'm trying to match a string containing certain characters, but not containing others. The problem is that if the string contains an allowed character, the expression finds a match, even though it contains invalid ones (nothing unusual, but not what I want).
The expression I'm using looks like this ([^abc][def])+.
So the question is: Can I define a group of characters, that if contained within the string, will stop the expression from matching the string?

Answer 1

You have to anchor your expression, to make sure no other characters are in the string. For example:

^[chars]+\z

Or you can simply invert the character class and you will get a match if an invalid character is present:

[^chars]

If you want to combine such checks with other expressions in the same regex you could use a lookahead:

^(?=[chars]+\z)expression