How to get only given captured group <regex> c++
c++, c++11, regex
Solution
The `regex_match` returns only a single match, with all the capturing group submatches (their number depends on how many groups there are in the pattern).
Here, you only get 1 match that contains two submatches: 1) whole match, 2) capture group 1 value.
To obtain the contents of the capturing group, you need to access the `smatches` object second element, `matches[1].str()` or `matches.str(1)`
Note that when you write `"<tag1.*>(.*)</tag1>\1"`, the `\1` is not parsed as a backreference, but as a char with octal code 1. Even if you defined a backreference (as `"<tag1.*>(.*)</tag1>\\1"`) you would require the whole text captured with the capturing group 1 to be repeated after `</tag1>` - that is definitely not what you want. Actually, I doubt this regex is any good, at least, you need to replace `".*"` with `"[\\s\\S]*?"`, but it is still a fragile approach to parse HTML with regex.
Problem
I want to extract tag's inner content. From the following string: ``` <tag1 val=123>Hello</tag1> ``` I just want to get ``` Hello ``` What I do: ``` string s = "<tag1 val=123>Hello</tag1>"; regex re("<tag1.*>(.*)</tag1>"); smatch matches; bool b = regex_match(s, matches, re); ``` But it returns two matches: ``` <tag1 val=123>Hello</tag1> Hello ``` And when I try to get only 1st captured group like this: ``` "<tag1.*>(.*)</tag1>\1" ``` I get zero matches. Please, advise.