bytes read_bytes(string file, int start, int number)
Reads a given amount of bytes from file.
If <start> is not given or 0, the file is read from the
beginning, else from the <start>th byte on. If <start> is
negative, it is counted from the end of the file.
<number> is the number of bytes to read. 0 or negative values
are possible, but not useful.
If <start> would be outside the actual size of the file, 0 is
returned instead of a string.
The maximum bytes being read per call is LIMIT_BYTE (see
read_file(E), write_bytes(E), write_file(E)