ifstream() -- which error happened? try/catch

Hi,

Background: I have lots of experience in C but not much in C++.

In C, if I call open() or fopen(), I can check the return value to determine if an error happened.  Then I can check errno to determine the error.

However, as I understand it, in C++ it is better to use try/catch so that error handling happens away from the main code area.  I have read several example of using try/catch with ifstream() on the web but the examples are all something like throw ( "An error occurred." );

That doesn't do me much good.  I want to know why I can't open the file.  Handling a permissions error is quite different than handling the file doesn't exist.

It occurs to me that I could throw something that includes errno.  My question is if that's a proper way to handle errors in C++ or should I be doing something else?

My question boils down to what is the correct OOP approach to handling ifstream errors in C++ when I want to know the nature of the error?

Hugh