C++ std::regex Regular Expressions Finding multiple matches

Question

I am trying to parse a certificate in c++ and decided it was a good opportunity to learn Regex. I just learned about regex an hour or so ago, so excuse my lack of knowledge.

I am looking for all of the OU's associated with an entry.

I am doing the following:

std::smatch OuMatches;
std::string myCertSubject = "O=\"My Company, Incorporated\", OU=Technician Level - A3, OU=Access Level - 1, CN=\"Name, My\", [email protected]";

std::regex subjectRx("OU=[[:w:]|[:s:]|[:digit:]|-]*", std::regex_constants::icase);
bool foundOU = std::regex_search(mySubject,OuMatches,subjectRx);

Why won't this give me all of the results (2) that match my reg ex? Is there a way to get this?

Answer 1

It looks like you're just trying to get a string that looks like OU=XXXXXXXXXXXXXXXXX followed by a comma or a semicolon.

This regex will do that:

OU=[^,;]+

What this means is the string OU=, followed by at least one character that isn't a comma or semicolon:

[^,;]+  

Here's a code sample using this regex to print the matches (based on the example here):

std::smatch OuMatches;
std::string myCertSubject = "O=\"My Company, Incorporated\", OU=Technician Level - A3, OU=Access Level - 1, CN=\"Name, My\", [email protected]";
std::regex subjectRx("OU=[^,;]+", std::regex_constants::icase);

std::regex_iterator<std::string::iterator> it (myCertSubject.begin(), myCertSubject.end(), subjectRx);
std::regex_iterator<std::string::iterator> end;

while (it != end)
{
    std::cout << it->str() << std::endl;
    ++it;
}

Answer 2

Try using a negated character class instead. I get the feeling your character classes aren't behaving like you think they are...

subjectRx("OU=[^,]*", std::regex_constants::icase);

[^,]* will match all characters except a comma.

As for the matches, try using a loop:

while (std::regex_search (mySubject,OuMatches,subjectRx)) {
    // do something
}

I don't know much C++, but I found this documentation page which I think should be a bit more useful.

The piece of code it has here is

while (std::regex_search (s,m,e)) {
    for (auto x:m) std::cout << x << " ";
    std::cout << std::endl;
    s = m.suffix().str();
}

EDIT: I just realise that you can have commas in the parameters like in O=, which won't be working with [^,]. Instead, you can use this regex:

OU=(?:[^,]|,(?!(?:[^"]*"[^"]*"[^"]*)*$))*

You can see an example with O= here.