C equivalence of std::find

I am trying to implement the C++11 std::find() in my C application. I looked online and found this reference: std::find in C++

My question, how can I use string.end(), string.begin() in C? Basically how would I use the function provided for std::find() with pure C?

So if I were to do:

std::string myString = "hello\n\n";
pos = myString.find("\n\n");

I would want the similar to this in C. How can I do this?