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<main role="main" aria-labelledby="module-Fcntl">
<h1 id="module-Fcntl" class="module">
module Fcntl
</h1>
<section class="description">
<p><a href="Fcntl.html"><code>Fcntl</code></a> loads the constants defined in the system's <fcntl.h> C header file, and used with both the fcntl(2) and open(2) POSIX system calls.</p>
<p>To perform a fcntl(2) operation, use IO::fcntl.</p>
<p>To perform an open(2) operation, use <a href="IO.html#method-c-sysopen"><code>IO::sysopen</code></a>.</p>
<p>The set of operations and constants available depends upon specific operating system. Some values listed below may not be supported on your system.</p>
<p>See your fcntl(2) man page for complete details.</p>
<p>Open /tmp/tempfile as a write-only file that is created if it doesn't exist:</p>
<pre class="ruby"><span class="ruby-identifier">require</span> <span class="ruby-string">'fcntl'</span>
<span class="ruby-identifier">fd</span> = <span class="ruby-constant">IO</span>.<span class="ruby-identifier">sysopen</span>(<span class="ruby-string">'/tmp/tempfile'</span>,
<span class="ruby-constant">Fcntl</span><span class="ruby-operator">::</span><span class="ruby-constant">O_WRONLY</span> <span class="ruby-operator">|</span> <span class="ruby-constant">Fcntl</span><span class="ruby-operator">::</span><span class="ruby-constant">O_EXCL</span> <span class="ruby-operator">|</span> <span class="ruby-constant">Fcntl</span><span class="ruby-operator">::</span><span class="ruby-constant">O_CREAT</span>)
<span class="ruby-identifier">f</span> = <span class="ruby-constant">IO</span>.<span class="ruby-identifier">open</span>(<span class="ruby-identifier">fd</span>)
<span class="ruby-identifier">f</span>.<span class="ruby-identifier">syswrite</span>(<span class="ruby-string">"TEMP DATA"</span>)
<span class="ruby-identifier">f</span>.<span class="ruby-identifier">close</span>
</pre>
<p>Get the flags on file <code>s</code>:</p>
<pre class="ruby"><span class="ruby-identifier">m</span> = <span class="ruby-identifier">s</span>.<span class="ruby-identifier">fcntl</span>(<span class="ruby-constant">Fcntl</span><span class="ruby-operator">::</span><span class="ruby-constant">F_GETFL</span>, <span class="ruby-value">0</span>)
</pre>
<p><a href="Set.html"><code>Set</code></a> the non-blocking flag on <code>f</code> in addition to the existing flags in <code>m</code>.</p>
<pre class="ruby"><span class="ruby-identifier">f</span>.<span class="ruby-identifier">fcntl</span>(<span class="ruby-constant">Fcntl</span><span class="ruby-operator">::</span><span class="ruby-constant">F_SETFL</span>, <span class="ruby-constant">Fcntl</span><span class="ruby-operator">::</span><span class="ruby-constant">O_NONBLOCK</span><span class="ruby-operator">|</span><span class="ruby-identifier">m</span>)
</pre>
</section>
<section id="5Buntitled-5D" class="documentation-section">
<section class="constants-list">
<header>
<h3>Constants</h3>
</header>
<dl>
<dt id="FD_CLOEXEC">FD_CLOEXEC
<dd><p><a href="Fcntl.html#FD_CLOEXEC"><code>FD_CLOEXEC</code></a></p>
<p>the value of the close-on-exec flag.</p>
<dt id="F_DUPFD">F_DUPFD
<dd><p><a href="Fcntl.html#F_DUPFD"><code>F_DUPFD</code></a></p>
<p>Duplicate a file descriptor to the minimum unused file descriptor greater than or equal to the argument.</p>
<p>The close-on-exec flag of the duplicated file descriptor is set. (Ruby uses F_DUPFD_CLOEXEC internally if available to avoid race condition. <a href="Fcntl.html#F_SETFD"><code>F_SETFD</code></a> is used if F_DUPFD_CLOEXEC is not available.)</p>
<dt id="F_GETFD">F_GETFD
<dd><p><a href="Fcntl.html#F_GETFD"><code>F_GETFD</code></a></p>
<p>Read the close-on-exec flag of a file descriptor.</p>
<dt id="F_GETFL">F_GETFL
<dd><p><a href="Fcntl.html#F_GETFL"><code>F_GETFL</code></a></p>
<p>Get the file descriptor flags. This will be one or more of the O_* flags.</p>
<dt id="F_GETLK">F_GETLK
<dd><p><a href="Fcntl.html#F_GETLK"><code>F_GETLK</code></a></p>
<p>Determine whether a given region of a file is locked. This uses one of the F_*LK flags.</p>
<dt id="F_RDLCK">F_RDLCK
<dd><p><a href="Fcntl.html#F_RDLCK"><code>F_RDLCK</code></a></p>
<p>Read lock for a region of a file</p>
<dt id="F_SETFD">F_SETFD
<dd><p><a href="Fcntl.html#F_SETFD"><code>F_SETFD</code></a></p>
<p><a href="Set.html"><code>Set</code></a> the close-on-exec flag of a file descriptor.</p>
<dt id="F_SETFL">F_SETFL
<dd><p><a href="Fcntl.html#F_SETFL"><code>F_SETFL</code></a></p>
<p><a href="Set.html"><code>Set</code></a> the file descriptor flags. This will be one or more of the O_* flags.</p>
<dt id="F_SETLK">F_SETLK
<dd><p><a href="Fcntl.html#F_SETLK"><code>F_SETLK</code></a></p>
<p>Acquire a lock on a region of a file. This uses one of the F_*LCK flags.</p>
<dt id="F_SETLKW">F_SETLKW
<dd><p><a href="Fcntl.html#F_SETLKW"><code>F_SETLKW</code></a></p>
<p>Acquire a lock on a region of a file, waiting if necessary. This uses one of the F_*LCK flags</p>
<dt id="F_UNLCK">F_UNLCK
<dd><p><a href="Fcntl.html#F_UNLCK"><code>F_UNLCK</code></a></p>
<p>Remove lock for a region of a file</p>
<dt id="F_WRLCK">F_WRLCK
<dd><p><a href="Fcntl.html#F_WRLCK"><code>F_WRLCK</code></a></p>
<p>Write lock for a region of a file</p>
<dt id="O_ACCMODE">O_ACCMODE
<dd><p><a href="Fcntl.html#O_ACCMODE"><code>O_ACCMODE</code></a></p>
<p>Mask to extract the read/write flags</p>
<dt id="O_APPEND">O_APPEND
<dd><p><a href="Fcntl.html#O_APPEND"><code>O_APPEND</code></a></p>
<p>Open the file in append mode</p>
<dt id="O_CREAT">O_CREAT
<dd><p><a href="Fcntl.html#O_CREAT"><code>O_CREAT</code></a></p>
<p>Create the file if it doesn't exist</p>
<dt id="O_EXCL">O_EXCL
<dd><p><a href="Fcntl.html#O_EXCL"><code>O_EXCL</code></a></p>
<p>Used with <a href="Fcntl.html#O_CREAT"><code>O_CREAT</code></a>, fail if the file exists</p>
<dt id="O_NDELAY">O_NDELAY
<dd><p><a href="Fcntl.html#O_NDELAY"><code>O_NDELAY</code></a></p>
<p>Open the file in non-blocking mode</p>
<dt id="O_NOCTTY">O_NOCTTY
<dd><p><a href="Fcntl.html#O_NOCTTY"><code>O_NOCTTY</code></a></p>
<p>Open TTY without it becoming the controlling TTY</p>
<dt id="O_NONBLOCK">O_NONBLOCK
<dd><p><a href="Fcntl.html#O_NONBLOCK"><code>O_NONBLOCK</code></a></p>
<p>Open the file in non-blocking mode</p>
<dt id="O_RDONLY">O_RDONLY
<dd><p><a href="Fcntl.html#O_RDONLY"><code>O_RDONLY</code></a></p>
<p>Open the file in read-only mode</p>
<dt id="O_RDWR">O_RDWR
<dd><p><a href="Fcntl.html#O_RDWR"><code>O_RDWR</code></a></p>
<p>Open the file in read-write mode</p>
<dt id="O_TRUNC">O_TRUNC
<dd><p><a href="Fcntl.html#O_TRUNC"><code>O_TRUNC</code></a></p>
<p>Truncate the file on open</p>
<dt id="O_WRONLY">O_WRONLY
<dd><p><a href="Fcntl.html#O_WRONLY"><code>O_WRONLY</code></a></p>
<p>Open the file in write-only mode.</p>
</dl>
</section>
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