There are two methods of finding and setting the stream position,
stream positioning and seeking. The current position of the
read/write pointer in a specified stream can be obtained by using
stream_position/2. It may be changed by using
stream_position/3. Alternatively, seek/4 may be used.
Seeking is more general, and stream positioning is more portable. The differences between them are:
stream_position/2 is equivalent to seek/4 with Offset = 0,
and Method = current.
stream_position/3 asks for stream position objects,
seek/4 uses integer expressions to represent the position or
offset. Stream position objects are obtained by calling
stream_position/[2,3], and are discussed in the reference page.
seek/4 is supported only on certain operating systems.
stream_position/3 is portable.