Javascript RegExp () allows you to specify a multi-line mode (m) which changes the behavior of ^ and $. ^ represents the start of the current line in multi-line mode, otherwise the start of the string $ represents the end of the current line in multi-line mode, otherwise the end of the string For example: this allows you to match something like semicolons at the end of a line where the next ...
Repetition in regex by default is greedy: they try to match as many reps as possible, and when this doesn't work and they have to backtrack, they try to match one fewer rep at a time, until a match of the whole pattern is found. As a result, when a match finally happens, a greedy repetition would match as many reps as possible.
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" option, try [\s\S]*. This means "match any number of characters that are either whitespace or non-whitespace" - effectively "match any string". Another option that only works for JavaScript (and is ...
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.
I'm reading the regular expressions reference and I'm thinking about ? and ?? characters. Could you explain me with some examples their usefulness? I don't understand them enough. thank you
It indicates that the subpattern is a non-capture subpattern. That means whatever is matched in (?:\w+\s), even though it's enclosed by () it won't appear in the list of matches, only (\w+) will. You're still looking for a specific pattern (in this case, a single whitespace character following at least one word), but you don't care what's actually matched.
Parentheses in regular expressions define groups, which is why you need to escape the parentheses to match the literal characters. So to modify the groups just remove all of the unescaped parentheses from the regex, then isolate the part of the regex that you want to put in a group and wrap it in parentheses. Groups are evaluated from left to right so if you want something to be in the second ...
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 "regex" could be regarded as misleading or incorrect) I'm guessing the fact that it worked for you was an isolated accident.
Regex Syntax Summary How Regexes Work JavaScript Regular Expressions Footnote †: The statement above that . matches any character is a simplification for pedagogical purposes that is not strictly true. Dot matches any character except newline, "\n", but in practice you rarely expect a pattern such as .+ to cross a newline boundary.
