int_type peek();
Behaves as UnformattedInputFunction. After constructing and testing the sentry object, reads the next character from the input stream without extracting it.
Parameters
(none).
Return value
If good() == true, returns the next character as obtained by rdbuf()->sgetc().
Otherwise, returns Traits::eof().
Exceptions
failure if an error occurred (the error state flag is not goodbit) and exceptions() is set to throw for that state.
If an internal operation throw