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<title>Seeks on a file pointer</title>
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<h1 class="refname">fseek</h1>
<p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">fseek</span> — <span class="dc-title">Seeks on a file pointer</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.fseek-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type">int</span> <span class="methodname"><strong>fseek</strong></span>
( <span class="methodparam"><span class="type">resource</span> <code class="parameter">$handle</code></span>
, <span class="methodparam"><span class="type">int</span> <code class="parameter">$offset</code></span>
[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$whence</code><span class="initializer"> = SEEK_SET</span></span>
] )</div>
<p class="para rdfs-comment">
Sets the file position indicator for the file referenced by
<em><code class="parameter">handle</code></em>. The new position, measured in bytes
from the beginning of the file, is obtained by adding
<em><code class="parameter">offset</code></em> to the position specified by
<em><code class="parameter">whence</code></em>.
</p>
<p class="para">
In general, it is allowed to seek past the end-of-file; if data is then
written, reads in any unwritten region between the end-of-file and the
sought position will yield bytes with value 0. However, certain streams
may not support this behavior, especially when they have an underlying
fixed size storage.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.fseek-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">handle</code></em></span>
<dd>
<p class="para">A file system pointer <span class="type"><a href="language.types.resource.html" class="type resource">resource</a></span>
that is typically created using <span class="function"><a href="function.fopen.html" class="function">fopen()</a></span>.</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">offset</code></em></span>
<dd>
<p class="para">
The offset.
</p>
<p class="para">
To move to a position before the end-of-file, you need to pass
a negative value in <em><code class="parameter">offset</code></em> and
set <em><code class="parameter">whence</code></em>
to <strong><code>SEEK_END</code></strong>.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">whence</code></em></span>
<dd>
<p class="para">
<em><code class="parameter">whence</code></em> values are:
<ul class="simplelist">
<li class="member"><strong><code>SEEK_SET</code></strong> - Set position equal to <em><code class="parameter">offset</code></em> bytes.</li>
<li class="member"><strong><code>SEEK_CUR</code></strong> - Set position to current location plus <em><code class="parameter">offset</code></em>.</li>
<li class="member"><strong><code>SEEK_END</code></strong> - Set position to end-of-file plus <em><code class="parameter">offset</code></em>.</li>
</ul>
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.fseek-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Upon success, returns 0; otherwise, returns -1.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.fseek-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-2393">
<p><strong>Example #1 <span class="function"><strong>fseek()</strong></span> example</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$fp </span><span style="color: #007700">= </span><span style="color: #0000BB">fopen</span><span style="color: #007700">(</span><span style="color: #DD0000">'somefile.txt'</span><span style="color: #007700">, </span><span style="color: #DD0000">'r'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// read some data<br /></span><span style="color: #0000BB">$data </span><span style="color: #007700">= </span><span style="color: #0000BB">fgets</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">, </span><span style="color: #0000BB">4096</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// move back to the beginning of the file<br />// same as rewind($fp);<br /></span><span style="color: #0000BB">fseek</span><span style="color: #007700">(</span><span style="color: #0000BB">$fp</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.fseek-notes">
<h3 class="title">Notes</h3>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
If you have opened the file in append (<em>a</em> or
<em>a+</em>) mode, any data you write to the file will always be
appended, regardless of the file position, and the result of calling
<span class="function"><strong>fseek()</strong></span> will be undefined.
</p>
</p></blockquote>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
Not all streams support seeking. For those that do not support seeking,
forward seeking from the current position is accomplished by reading
and discarding data; other forms of seeking will fail.
</p>
</p></blockquote>
</div>
<div class="refsect1 seealso" id="refsect1-function.fseek-seealso">
<h3 class="title">See Also</h3>
<p class="para">
<ul class="simplelist">
<li class="member"> <span class="function"><a href="function.ftell.html" class="function" rel="rdfs-seeAlso">ftell()</a> - Returns the current position of the file read/write pointer</span></li>
<li class="member"> <span class="function"><a href="function.rewind.html" class="function" rel="rdfs-seeAlso">rewind()</a> - Rewind the position of a file pointer</span></li>
</ul>
</p>
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