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.
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.
