istream库下
istream& getline (char* s, streamsize n ); istream& getline (char* s, streamsize n, char delim );
从istream输入流中读取字符传入字符串s，个数为n
string库下
istream& getline (istream& is, string& str, char delim); istream& getline (istream&& is, string& str, char delim); istream& getline (istream& is, string& str); istream& getline (istream&& is, string& str);
从is中读取一行传入字符串str，截至到字符delim