Returns a string of up to length characters from the input stream. The stream advances the read pointer by the number of characters read. If you omit length, it defaults to 1. If you specify start, this positions the read pointer before reading. The start value must be a positive whole number within the bounds of the stream. If the value is not a positive whole number, a syntax condition is raised. When the value is past the end of the stream, the empty string is returned and the NOTREADY condition is raised. If the stream is not already open, the stream attempts to open for reading and writing. If that fails, the stream opens for input only.