[Language pedant: although it's legal C, the use of cerr and endl and << is more likely to occur in C++!]

<< is C++ only.

<< is the left-shift operator in C, so the OP's code is syntactically valid C.

It ought not to compile though, since it's trying to shift cerr by a string!

Thanks. Sorry. I'm stupid...

"Goddamn operator overloading" -- Rev Wright

Strangest language feature...