带有捕获组的 C++ 正则表达式字符串文字

Question

I have a std::string containing backslashes, double quotes. I want to extract a substring using capture group, but I am not able to get the syntax right. eg

std::string str(R"(some\"string"name":"john"\"lastname":"doe")");  //==> want to extract "john"
std::regex re(R"(some\"string"name":")"(.*)R"("\"lastname":"doe")");    //==> wrong syntax

std::smatch match;
std::string name;
if (std::regex_search(str, match, re) && match.size() > 1)
{
    name = match.str(1);
}

Answer 1

1. Use a delimeter that does not occur in the string. Eg R"~( .... )~"

2. You still need to escape the \\ for regex. To match \\ literally use \\\\ .

3. You probably want to stop as soon as the shortest possible match is found. So use (.*?) :

    std::regex re(R"~(some\\\\"string"name":"(.*?)"\\\\"lastname":"doe")~");