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<a name="ftell_002c-ftello_002d_002d_002dreturn-position-in-a-stream-or-file"></a>
<h3 class="section">4.29 <code>ftell</code>, <code>ftello</code>&mdash;return position in a stream or file</h3>
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<p><strong>Synopsis</strong>
</p><div class="example">
<pre class="example">#include &lt;stdio.h&gt;
long ftell(FILE *<var>fp</var>);
off_t ftello(FILE *<var>fp</var>);
long _ftell_r(struct _reent *<var>ptr</var>, FILE *<var>fp</var>);
off_t _ftello_r(struct _reent *<var>ptr</var>, FILE *<var>fp</var>);

</pre></div>
<p><strong>Description</strong><br>
Objects of type <code>FILE</code> can have a &ldquo;position&rdquo; that records how much
of the file your program has already read.  Many of the <code>stdio</code> functions
depend on this position, and many change it as a side effect.
</p>
<p>The result of <code>ftell</code>/<code>ftello</code> is the current position for a file
identified by <var>fp</var>.  If you record this result, you can later
use it with <code>fseek</code>/<code>fseeko</code> to return the file to this
position.  The difference between <code>ftell</code> and <code>ftello</code> is that
<code>ftell</code> returns <code>long</code> and <code>ftello</code> returns <code>off_t</code>.
</p>
<p>In the current implementation, <code>ftell</code>/<code>ftello</code> simply uses a character
count to represent the file position; this is the same number that
would be recorded by <code>fgetpos</code>.
</p>
<br>
<p><strong>Returns</strong><br>
<code>ftell</code>/<code>ftello</code> return the file position, if possible.  If they cannot do
this, they return <code>-1L</code>.  Failure occurs on streams that do not support
positioning; the global <code>errno</code> indicates this condition with the
value <code>ESPIPE</code>.
</p>
<br>
<p><strong>Portability</strong><br>
<code>ftell</code> is required by the ANSI C standard, but the meaning of its
result (when successful) is not specified beyond requiring that it be
acceptable as an argument to <code>fseek</code>.  In particular, other
conforming C implementations may return a different result from
<code>ftell</code> than what <code>fgetpos</code> records.
</p>
<p><code>ftello</code> is defined by the Single Unix specification.
</p>
<p>No supporting OS subroutines are required.
</p>
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