basic_istream::putback

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basic_istream::putback

basic_istream& putback(E c);

The unformatted input function puts back c, if possible, as if by calling rdbuf()->sputbackc(). If rdbuf() is a null pointer, or if the call to sputbackc returns T::eof(), the function calls setstate(badbit). In any case, it returns *this.