
written.  &rsquo;count&rsquo; is the maximum number of bytes to be written.  This
procedure returns the number of bytes actually written, which can be
less than &rsquo;count&rsquo; bytes.  The sum of &rsquo;begin&rsquo; and &rsquo;count&rsquo; must not be
more than the length of the bytevector.  The use of a separate &rsquo;begin&rsquo;
index enables the same bytevector to be written from repeatedly until
all of it has been sent.
</p>
<p>Provided &rsquo;fd&rsquo; is non-blocking, this procedure returns str