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<a name="fwide_002d_002d_002dset-and-determine-the-orientation-of-a-FILE-stream"></a>
<h3 class="section">4.31 <code>fwide</code>&mdash;set and determine the orientation of a FILE stream</h3>
<a name="index-fwide"></a>
<a name="index-_005ffwide_005fr"></a>
<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">#include &lt;wchar.h&gt;
int fwide(FILE *<var>fp</var>, int <var>mode</var>);
int _fwide_r(struct _reent *<var>ptr</var>, FILE *<var>fp</var>, int <var>mode</var>);
</pre></div>
<p><strong>Description</strong><br>
When <var>mode</var> is zero, the <code>fwide</code> function determines the current
orientation of <var>fp</var>. It returns a value &gt; 0 if <var>fp</var> is
wide-character oriented, i.e. if wide character I/O is permitted but
char I/O is disallowed. It returns a value &lt; 0 if <var>fp</var> is byte
oriented, i.e. if char I/O is permitted but wide character I/O is
disallowed. It returns zero if <var>fp</var> has no orientation yet; in
this case the next I/O operation might change the orientation (to byte
oriented if it is a char I/O operation, or to wide-character oriented
if it is a wide character I/O operation).
</p>
<p>Once a stream has an orientation, it cannot be changed and persists
until the stream is closed, unless the stream is re-opened with freopen,
which removes the orientation of the stream.
</p>
<p>When <var>mode</var> is non-zero, the <code>fwide</code> function first attempts to set
<var>fp</var>&rsquo;s orientation (to wide-character oriented if <var>mode</var> &gt; 0, or to
byte oriented if <var>mode</var> &lt; 0). It then returns a value denoting the
current orientation, as above.
</p>
<br>
<p><strong>Returns</strong><br>
The <code>fwide</code> function returns <var>fp</var>&rsquo;s orientation, after possibly
changing it. A return value &gt; 0 means wide-character oriented. A return
value &lt; 0 means byte oriented. A return value of zero means undecided.
</p>
<br>
<p><strong>Portability</strong><br>
C99, POSIX.1-2001.
</p>
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