This function returns the current file position (in bytes, 0-based) for
This value is typically fed to the
function at some future time
to get back to the current position.
may be an expression whose value gives the name of the
actual filehandle, or a reference to a filehandle object.
is omitted, the function returns the
position of the file last read. File positions are only meaningful on
regular files. Devices, pipes, and sockets have no file position.
for an example.