@deffn {Scheme Procedure} seek fd_port offset whence
@deffnx {C Function} scm_seek (fd_port, offset, whence)
Sets the current position of @var{fd_port} to the integer
-@var{offset}, which is interpreted according to the value of
-@var{whence}.
+@var{offset}. For a file port, @var{offset} is expressed
+as a number of bytes; for other types of ports, such as string
+ports, @var{offset} is an abstract representation of the
+position within the port's data, not necessarily expressed
+as a number of bytes. @var{offset} is interpreted according to
+the value of @var{whence}.
One of the following variables should be supplied for
@var{whence}:
If @var{fd_port} is a file descriptor, the underlying system
call is @code{lseek}. @var{port} may be a string port.
-The value returned is the new position in the file. This means
+The value returned is the new position in @var{fd_port}. This means
that the current position of a port can be obtained using:
@lisp
(seek port 0 SEEK_CUR)