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<title>Performs a c library fcntl on fd</title>
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<h1 class="refname">dio_fcntl</h1>
<p class="verinfo">(PHP 4 >= 4.2.0, PHP 5 <= 5.0.5)</p><p class="refpurpose"><span class="refname">dio_fcntl</span> — <span class="dc-title">Performs a c library fcntl on fd</span></p>
</div>
<div class="refsect1 description" id="refsect1-function.dio-fcntl-description">
<h3 class="title">Description</h3>
<div class="methodsynopsis dc-description">
<span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <span class="methodname"><strong>dio_fcntl</strong></span>
( <span class="methodparam"><span class="type">resource</span> <code class="parameter">$fd</code></span>
, <span class="methodparam"><span class="type">int</span> <code class="parameter">$cmd</code></span>
[, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$args</code></span>
] )</div>
<p class="para rdfs-comment">
The <span class="function"><strong>dio_fcntl()</strong></span> function performs the
operation specified by <em><code class="parameter">cmd</code></em> on the file
descriptor <em><code class="parameter">fd</code></em>. Some commands require
additional arguments <em><code class="parameter">args</code></em> to be supplied.
</p>
</div>
<div class="refsect1 parameters" id="refsect1-function.dio-fcntl-parameters">
<h3 class="title">Parameters</h3>
<p class="para">
<dl>
<dt>
<span class="term"><em><code class="parameter">fd</code></em></span>
<dd>
<p class="para">
The file descriptor returned by <span class="function"><a href="function.dio-open.html" class="function">dio_open()</a></span>.
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">cmd</code></em></span>
<dd>
<p class="para">
Can be one of the following operations:
<ul class="itemizedlist">
<li class="listitem">
<p class="para">
<strong><code>F_SETLK</code></strong> - Lock is set or cleared. If the lock
is held by someone else <span class="function"><strong>dio_fcntl()</strong></span> returns
-1.
</p>
</li>
<li class="listitem">
<p class="para">
<strong><code>F_SETLKW</code></strong> - like <strong><code>F_SETLK</code></strong>,
but in case the lock is held by someone else,
<span class="function"><strong>dio_fcntl()</strong></span> waits until the lock is released.
</p>
</li>
<li class="listitem">
<p class="para">
<strong><code>F_GETLK</code></strong> - <span class="function"><strong>dio_fcntl()</strong></span>
returns an associative array (as described above) if someone else
prevents lock. If there is no obstruction key "type" will set
to <strong><code>F_UNLCK</code></strong>.
</p>
</li>
<li class="listitem">
<p class="para">
<strong><code>F_DUPFD</code></strong> - finds the lowest numbered available
file descriptor greater than or equal to <em><code class="parameter">args</code></em>
and returns them.
</p>
</li>
<li class="listitem">
<p class="para">
<strong><code>F_SETFL</code></strong> - Sets the file descriptors flags to
the value specified by <em><code class="parameter">args</code></em>, which can be
<strong><code>O_APPEND</code></strong>, <strong><code>O_NONBLOCK</code></strong> or
<strong><code>O_ASYNC</code></strong>. To use <strong><code>O_ASYNC</code></strong>
you will need to use the <a href="ref.pcntl.html" class="link">PCNTL</a>
extension.
</p>
</li>
</ul>
</p>
</dd>
</dt>
<dt>
<span class="term"><em><code class="parameter">args</code></em></span>
<dd>
<p class="para">
<em><code class="parameter">args</code></em> is an associative array, when
<em><code class="parameter">cmd</code></em> is <strong><code>F_SETLK</code></strong> or
<strong><code>F_SETLLW</code></strong>, with the following keys:
<ul class="itemizedlist">
<li class="listitem">
<p class="para">
<em>start</em> - offset where lock begins
</p>
</li>
<li class="listitem">
<p class="para">
<em>length</em> - size of locked area. zero means to end
of file
</p>
</li>
<li class="listitem">
<p class="para">
<em>whence</em> - Where l_start is relative to: can be
<strong><code>SEEK_SET</code></strong>,
<strong><code>SEEK_END</code></strong> and <strong><code>SEEK_CUR</code></strong>
</p>
</li>
<li class="listitem">
<p class="para">
<em>type</em> - type of lock: can be
<strong><code>F_RDLCK</code></strong> (read lock),
<strong><code>F_WRLCK</code></strong> (write lock) or
<strong><code>F_UNLCK</code></strong> (unlock)
</p>
</li>
</ul>
</p>
</dd>
</dt>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.dio-fcntl-returnvalues">
<h3 class="title">Return Values</h3>
<p class="para">
Returns the result of the C call.
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.dio-fcntl-examples">
<h3 class="title">Examples</h3>
<p class="para">
<div class="example" id="example-2329">
<p><strong>Example #1 Setting and clearing a lock</strong></p>
<div class="example-contents">
<div class="phpcode"><code><span style="color: #000000">
<span style="color: #0000BB"><?php<br /><br />$fd </span><span style="color: #007700">= </span><span style="color: #0000BB">dio_open</span><span style="color: #007700">(</span><span style="color: #DD0000">'/dev/ttyS0'</span><span style="color: #007700">, </span><span style="color: #0000BB">O_RDWR</span><span style="color: #007700">);<br /><br />if (</span><span style="color: #0000BB">dio_fcntl</span><span style="color: #007700">(</span><span style="color: #0000BB">$fd</span><span style="color: #007700">, </span><span style="color: #0000BB">F_SETLK</span><span style="color: #007700">, Array(</span><span style="color: #DD0000">"type"</span><span style="color: #007700">=></span><span style="color: #0000BB">F_WRLCK</span><span style="color: #007700">)) == -</span><span style="color: #0000BB">1</span><span style="color: #007700">) {<br /> </span><span style="color: #FF8000">// the file descriptor appears locked<br /> </span><span style="color: #007700">echo </span><span style="color: #DD0000">"The lock can not be cleared. It is held by someone else."</span><span style="color: #007700">;<br />} else {<br /> echo </span><span style="color: #DD0000">"Lock successfully set/cleared"</span><span style="color: #007700">;<br />}<br /><br /></span><span style="color: #0000BB">dio_close</span><span style="color: #007700">(</span><span style="color: #0000BB">$fd</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
</span>
</code></div>
</div>
</div>
</p>
</div>
<div class="refsect1 notes" id="refsect1-function.dio-fcntl-notes">
<h3 class="title">Notes</h3>
<blockquote class="note"><p><strong class="note">Note</strong>: <span class="simpara">This function is not
implemented on Windows platforms.</span></p></blockquote>
</div>
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