int rdstate() const;
Returns the current error state as specified by the following masks (ios enumerators):
| Value | Meaning |
| ios::goodbit | No error condition |
| ios::eofbit | End of file reached |
| ios::failbit | A possibly recoverable formatting or conversion error |
| ios::badbit | A severe I/O error or unknown state |
The returned value can be tested against a mask with the AND (&) operator.