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<table class="head">
<tr>
<td class="head-ltitle">FD(4)</td>
<td class="head-vol">Device Drivers Manual</td>
<td class="head-rtitle">FD(4)</td>
</tr>
</table>
<div class="manual-text">
<section class="Sh">
<h1 class="Sh" id="NAME"><a class="permalink" href="#NAME">NAME</a></h1>
<p class="Pp"><code class="Nm">fd</code>, <code class="Nm">stdin</code>,
<code class="Nm">stdout</code>, <code class="Nm">stderr</code> —
<span class="Nd">file descriptor files</span></p>
</section>
<section class="Sh">
<h1 class="Sh" id="DESCRIPTION"><a class="permalink" href="#DESCRIPTION">DESCRIPTION</a></h1>
<p class="Pp">The files <span class="Pa">/dev/fd/0</span> through
<span class="Pa">/dev/fd/#</span> refer to file descriptors which can be
accessed through the file system. If the file descriptor is open and the
mode the file is being opened with is a subset of the mode of the existing
descriptor, the call:</p>
<div class="Bd Pp Bd-indent Li">
<pre>fd = open("/dev/fd/0", mode);</pre>
</div>
<p class="Pp">and the call:</p>
<div class="Bd Pp Bd-indent Li">
<pre>fd = fcntl(0, F_DUPFD, 0);</pre>
</div>
<p class="Pp">are equivalent.</p>
<p class="Pp">Opening the files <span class="Pa">/dev/stdin</span>,
<span class="Pa">/dev/stdout</span> and <span class="Pa">/dev/stderr</span>
is equivalent to the following calls:</p>
<div class="Bd Pp Bd-indent Li">
<pre>fd = fcntl(STDIN_FILENO, F_DUPFD, 0);
fd = fcntl(STDOUT_FILENO, F_DUPFD, 0);
fd = fcntl(STDERR_FILENO, F_DUPFD, 0);</pre>
</div>
<p class="Pp">Flags to the <a class="Xr">open(2)</a> call other than
<code class="Dv">O_RDONLY</code>, <code class="Dv">O_WRONLY</code> and
<code class="Dv">O_RDWR</code> are ignored.</p>
</section>
<section class="Sh">
<h1 class="Sh" id="FILES"><a class="permalink" href="#FILES">FILES</a></h1>
<dl class="Bl-tag Bl-compact">
<dt><span class="Pa">/dev/fd/#</span></dt>
<dd style="width: auto;"> </dd>
<dt><span class="Pa">/dev/stdin</span></dt>
<dd style="width: auto;"> </dd>
<dt><span class="Pa">/dev/stdout</span></dt>
<dd style="width: auto;"> </dd>
<dt><span class="Pa">/dev/stderr</span></dt>
<dd style="width: auto;"> </dd>
</dl>
</section>
<section class="Sh">
<h1 class="Sh" id="SEE_ALSO"><a class="permalink" href="#SEE_ALSO">SEE
ALSO</a></h1>
<p class="Pp"><a class="Xr">tty(4)</a>, <a class="Xr">mount_fdesc(8)</a></p>
<section class="Ss">
<h2 class="Ss" id="NOTE"><a class="permalink" href="#NOTE">NOTE</a></h2>
<p class="Pp">The floppy disk driver on some ports is also called
<code class="Nm">fd</code>; see <a class="Xr">fdc(4)</a> for its
documentation.</p>
</section>
</section>
</div>
<table class="foot">
<tr>
<td class="foot-date">December 29, 2013</td>
<td class="foot-os">NetBSD 10.1</td>
</tr>
</table>
|
