Saturday 12th December 2015: 2.09pm. Link shared: http://www.nedprod.com/errcmp.html
One of the really great things about wip Boost.Outcome (https://github.com/ned14/boost.outcome) is the ability to write C++ that has the same hard control flow behaviour guarantees as C, but with all the productivity C++ 14 provides. This makes it much easier to write systems code which cannot surprise you, and it is what the being rewritten wip Boost.AFIO v2 (https://github.com/BoostGSoC13/boost.afio) uses.
To that end, a simple table of POSIX errno codes is invaluable and there was a great one at http://www.ioplex.com/~miallen/errcmp.html which sadly has been down for a few weeks now, so before Google deletes it from its cache I've mirrored the original at http://www.nedprod.com/errcmp.html. Enjoy!