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<a name="File-Positioning"></a>
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<p>
Previous: <a href="EOF-and-Errors.html#EOF-and-Errors" accesskey="p" rel="prev">EOF and Errors</a>, Up: <a href="C_002dStyle-I_002fO-Functions.html#C_002dStyle-I_002fO-Functions" accesskey="u" rel="up">C-Style I/O Functions</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html#Concept-Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<a name="File-Positioning-1"></a>
<h4 class="subsection">14.2.19 File Positioning</h4>

<p>Three functions are available for setting and determining the position of
the file pointer for a given file.
</p>
<a name="XREFftell"></a><dl>
<dt><a name="index-ftell"></a>: <em><var>pos</var> =</em> <strong>ftell</strong> <em>(<var>fid</var>)</em></dt>
<dd><p>Return the position of the file pointer as the number of characters from the
beginning of the file specified by file descriptor <var>fid</var>.
</p>
<p><strong>See also:</strong> <a href="#XREFfseek">fseek</a>, <a href="#XREFfrewind">frewind</a>, <a href="EOF-and-Errors.html#XREFfeof">feof</a>, <a href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>.
</p></dd></dl>


<a name="XREFfseek"></a><dl>
<dt><a name="index-fseek"></a>: <em></em> <strong>fseek</strong> <em>(<var>fid</var>, <var>offset</var>)</em></dt>
<dt><a name="index-fseek-1"></a>: <em></em> <strong>fseek</strong> <em>(<var>fid</var>, <var>offset</var>, <var>origin</var>)</em></dt>
<dt><a name="index-fseek-2"></a>: <em><var>status</var> =</em> <strong>fseek</strong> <em>(&hellip;)</em></dt>
<dd><p>Set the file pointer to the location <var>offset</var> within the file <var>fid</var>.
</p>
<p>The pointer is positioned <var>offset</var> characters from the <var>origin</var>,
which may be one of the predefined variables <code><span class="nolinebreak">SEEK_CUR</span></code><!-- /@w --> (current
position), <code><span class="nolinebreak">SEEK_SET</span></code><!-- /@w --> (beginning), or <code><span class="nolinebreak">SEEK_END</span></code><!-- /@w --> (end of
file) or strings <code>&quot;cof&quot;</code>, <code>&quot;bof&quot;</code> or <code>&quot;eof&quot;</code>.  If
<var>origin</var> is omitted, <code><span class="nolinebreak">SEEK_SET</span></code><!-- /@w --> is assumed.  <var>offset</var> may
be positive, negative, or zero but not all combinations of <var>origin</var> and
<var>offset</var> can be realized.
</p>
<p><code>fseek</code> returns 0 on success and -1 on error.
</p>
<p><strong>See also:</strong> <a href="Line_002dOriented-Input.html#XREFfskipl">fskipl</a>, <a href="#XREFfrewind">frewind</a>, <a href="#XREFftell">ftell</a>, <a href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>.
</p></dd></dl>


<a name="XREFSEEK_005fSET"></a><dl>
<dt><a name="index-SEEK_005fSET"></a>: <em></em> <strong>SEEK_SET</strong> <em>()</em></dt>
<dt><a name="index-SEEK_005fCUR"></a>: <em></em> <strong>SEEK_CUR</strong> <em>()</em></dt>
<dt><a name="index-SEEK_005fEND"></a>: <em></em> <strong>SEEK_END</strong> <em>()</em></dt>
<dd><p>Return the numerical value to pass to <code>fseek</code> to perform one of the
following actions:
</p>
<dl compact="compact">
<dt><code>SEEK_SET</code></dt>
<dd><p>Position file relative to the beginning.
</p>
</dd>
<dt><code>SEEK_CUR</code></dt>
<dd><p>Position file relative to the current position.
</p>
</dd>
<dt><code>SEEK_END</code></dt>
<dd><p>Position file relative to the end.
</p></dd>
</dl>

<p><strong>See also:</strong> <a href="#XREFfseek">fseek</a>.
</p></dd></dl>


<a name="XREFfrewind"></a><dl>
<dt><a name="index-frewind"></a>: <em></em> <strong>frewind</strong> <em>(<var>fid</var>)</em></dt>
<dt><a name="index-frewind-1"></a>: <em><var>status</var> =</em> <strong>frewind</strong> <em>(<var>fid</var>)</em></dt>
<dd><p>Move the file pointer to the beginning of the file specified by file
descriptor <var>fid</var>.
</p>
<p><code>frewind</code> returns 0 for success, and -1 if an error is encountered.  It
is equivalent to <code>fseek (<var>fid</var>, 0, SEEK_SET)</code>.
</p>
<p><strong>See also:</strong> <a href="#XREFfseek">fseek</a>, <a href="#XREFftell">ftell</a>, <a href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>.
</p></dd></dl>


<p>The following example stores the current file position in the variable
<code>marker</code>, moves the pointer to the beginning of the file, reads
four characters, and then returns to the original position.
</p>
<div class="example">
<pre class="example">marker = ftell (myfile);
frewind (myfile);
fourch = fgets (myfile, 4);
fseek (myfile, marker, SEEK_SET);
</pre></div>


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