Oct 15, 2009 · May I know what ?= means in a regular expression? For example, what is its significance in this expression: (?=.*\\d).

Dec 8, 2018 · The regex compiles fine, and there are already JUnit tests that show how it works. It's just that I'm a bit confused about why the first question mark and colon are there.

Be aware that the first ^ in this answer gives the regex a completely different meaning: It makes the regular expression look only for matches starting from the beginning of the string.

Jan 22, 2009 · In regex in general, ^ is negation only at the beginning of a character class. Unless CMake is doing something really funky (to the point where calling their pattern matching language …

I need to extract from a string a set of characters which are included between two delimiters, without returning the delimiters themselves. A simple example should be helpful: Target: extract the

Nov 12, 2009 · I need a regex which will allow only A-Z, a-z, 0-9, the _ character, and dot (.) in the input. I tried: [A-Za-z0-9_.] But, it did not work. How can I fix it?

By putting ^ at the beginning of your regex and $ at the end, you ensure that no other characters are allowed before or after your regex. For example, the regex [0-9] matches the strings "9" as well as …

While writing this answer, I had to match exclusively on linebreaks instead of using the s-flag (dotall - dot matches linebreaks). The sites usually used to test regular expressions behave diffe...

In case it is JS it indicates the start and end of the regex, like quotes for strings. stackoverflow.com/questions/15661969/…

Normally the dot matches any character except newlines. So if .* isn't working, set the "dot matches newlines, too" option (or use (?s).*). If you're using JavaScript, which doesn't have a "dotall" …