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<h4 class="subsection" id="File-Positioning-1"><span>14.2.19 File Positioning<a class="copiable-link" href="#File-Positioning-1"> ¶</a></span></h4>
<p>Three functions are available for setting and determining the position of
the file pointer for a given file.
</p>
<a class="anchor" id="XREFftell"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-ftell"><span><code class="def-type"><var class="var">pos</var> =</code> <strong class="def-name">ftell</strong> <code class="def-code-arguments">(<var class="var">fid</var>)</code><a class="copiable-link" href="#index-ftell"> ¶</a></span></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 class="var">fid</var>.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFfseek">fseek</a>, <a class="ref" href="#XREFfrewind">frewind</a>, <a class="ref" href="EOF-and-Errors.html#XREFfeof">feof</a>, <a class="ref" href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>.
</p></dd></dl>
<a class="anchor" id="XREFfseek"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-fseek"><span><code class="def-type"><var class="var">status</var> =</code> <strong class="def-name">fseek</strong> <code class="def-code-arguments">(<var class="var">fid</var>, <var class="var">offset</var>)</code><a class="copiable-link" href="#index-fseek"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-fseek-1"><span><code class="def-type"><var class="var">status</var> =</code> <strong class="def-name">fseek</strong> <code class="def-code-arguments">(<var class="var">fid</var>, <var class="var">offset</var>, <var class="var">origin</var>)</code><a class="copiable-link" href="#index-fseek-1"> ¶</a></span></dt>
<dd><p>Set the file pointer to the location <var class="var">offset</var> within the file <var class="var">fid</var>.
</p>
<p>The pointer is positioned <var class="var">offset</var> characters from the <var class="var">origin</var>, which
may be one of the predefined variables <code class="code">SEEK_SET</code><!-- /@w --> (beginning),
<code class="code">SEEK_CUR</code><!-- /@w --> (current position), or <code class="code">SEEK_END</code><!-- /@w --> (end of file)
or strings <code class="code">"bof"</code>, <code class="code">"cof"</code>, or
<code class="code">"eof"</code>. If <var class="var">origin</var> is omitted, <code class="code">SEEK_SET</code><!-- /@w --> is
assumed. <var class="var">offset</var> may be positive, negative, or zero but not all
combinations of <var class="var">origin</var> and <var class="var">offset</var> can be realized.
</p>
<p><code class="code">fseek</code> returns 0 on success and -1 on error.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="Line_002dOriented-Input.html#XREFfskipl">fskipl</a>, <a class="ref" href="#XREFfrewind">frewind</a>, <a class="ref" href="#XREFftell">ftell</a>, <a class="ref" href="Opening-and-Closing-Files.html#XREFfopen">fopen</a>, <a class="ref" href="#XREFSEEK_005fSET">SEEK_SET</a>, <a class="ref" href="#XREFSEEK_005fCUR">SEEK_CUR</a>, <a class="ref" href="#XREFSEEK_005fEND">SEEK_END</a>.
</p></dd></dl>
<a class="anchor" id="XREFSEEK_005fSET"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-SEEK_005fSET"><span><code class="def-type"><var class="var">fseek_origin</var> =</code> <strong class="def-name">SEEK_SET</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-SEEK_005fSET"> ¶</a></span></dt>
<dd><p>Return the numerical value to pass to <code class="code">fseek</code> to position the file pointer
relative to the beginning of the file.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFSEEK_005fCUR">SEEK_CUR</a>, <a class="ref" href="#XREFSEEK_005fEND">SEEK_END</a>, <a class="ref" href="#XREFfseek">fseek</a>.
</p></dd></dl>
<a class="anchor" id="XREFSEEK_005fCUR"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-SEEK_005fCUR"><span><code class="def-type"><var class="var">fseek_origin</var> =</code> <strong class="def-name">SEEK_CUR</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-SEEK_005fCUR"> ¶</a></span></dt>
<dd><p>Return the numerical value to pass to <code class="code">fseek</code> to position the file pointer
relative to the current position.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFSEEK_005fSET">SEEK_SET</a>, <a class="ref" href="#XREFSEEK_005fEND">SEEK_END</a>, <a class="ref" href="#XREFfseek">fseek</a>.
</p></dd></dl>
<a class="anchor" id="XREFSEEK_005fEND"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-SEEK_005fEND"><span><code class="def-type"><var class="var">fseek_origin</var> =</code> <strong class="def-name">SEEK_END</strong> <code class="def-code-arguments">()</code><a class="copiable-link" href="#index-SEEK_005fEND"> ¶</a></span></dt>
<dd><p>Return the numerical value to pass to <code class="code">fseek</code> to position the file pointer
relative to the end of the file.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFSEEK_005fSET">SEEK_SET</a>, <a class="ref" href="#XREFSEEK_005fCUR">SEEK_CUR</a>, <a class="ref" href="#XREFfseek">fseek</a>.
</p></dd></dl>
<a class="anchor" id="XREFfrewind"></a><span style="display:block; margin-top:-4.5ex;"> </span>
<dl class="first-deftypefn">
<dt class="deftypefn" id="index-frewind"><span><strong class="def-name">frewind</strong> <code class="def-code-arguments">(<var class="var">fid</var>)</code><a class="copiable-link" href="#index-frewind"> ¶</a></span></dt>
<dt class="deftypefnx def-cmd-deftypefn" id="index-frewind-1"><span><code class="def-type"><var class="var">status</var> =</code> <strong class="def-name">frewind</strong> <code class="def-code-arguments">(<var class="var">fid</var>)</code><a class="copiable-link" href="#index-frewind-1"> ¶</a></span></dt>
<dd><p>Move the file pointer to the beginning of the file specified by file
descriptor <var class="var">fid</var>.
</p>
<p>If an output <var class="var">status</var> is requested then <code class="code">frewind</code> returns 0 for
success, and -1 if an error is encountered.
</p>
<p>Programming Note: <code class="code">frewind</code> is equivalent to
<code class="code">fseek (<var class="var">fid</var>, 0, SEEK_SET)</code>.
</p>
<p><strong class="strong">See also:</strong> <a class="ref" href="#XREFfseek">fseek</a>, <a class="ref" href="#XREFftell">ftell</a>, <a class="ref" 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 class="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">
<div class="group"><pre class="example-preformatted">marker = ftell (myfile);
frewind (myfile);
fourch = fgets (myfile, 4);
fseek (myfile, marker, SEEK_SET);
</pre></div></div>
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