Read[stream]
Read[stream, type]
str = StringToStream["abc123"];
Read[str, String]
str = StringToStream["abc 123"];
Read[str, Word]
Read[str, Word]
str = StringToStream["123, 4"];
Read[str, Number]
Read[str, Number]
str = StringToStream["123 abc"];
Read[str, {Number, Word}]