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<a href="../libudev/index.html">gudev </a><span style="float:right">systemd 208</span><hr><div class="refentry"><a name="sd_is_fifo"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>sd_is_fifo, sd_is_socket, sd_is_socket_inet, sd_is_socket_unix, sd_is_mq — Check the type of a file descriptor</p></div><div class="refsynopsisdiv"><h2>Synopsis</h2><div class="funcsynopsis"><pre class="funcsynopsisinfo">#include <systemd/sd-daemon.h></pre><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_is_fifo</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">path</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_is_socket</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">family</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">type</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">listening</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_is_socket_inet</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">family</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">type</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">listening</var>, </td></tr><tr><td> </td><td>uint16_t <var class="pdparam">port</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_is_socket_unix</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">type</var>, </td></tr><tr><td> </td><td>int <var class="pdparam">listening</var>, </td></tr><tr><td> </td><td>const char* <var class="pdparam">path</var>, </td></tr><tr><td> </td><td>size_t <var class="pdparam">length</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table border="0" class="funcprototype-table" summary="Function synopsis" style="cellspacing: 0; cellpadding: 0;"><tr><td><code class="funcdef">int <b class="fsfunc">sd_is_mq</b>(</code></td><td>int <var class="pdparam">fd</var>, </td></tr><tr><td> </td><td>const char *<var class="pdparam">path</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1"><a name="idm274698824000"></a><h2 id="Description">Description<a class="headerlink" title="Permalink to this headline" href="#Description">¶</a></h2><p><code class="function">sd_is_fifo()</code> may be called
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to check whether the specified file descriptor refers
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to a FIFO or pipe. If the <em class="parameter"><code>path</code></em>
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parameter is not <code class="constant">NULL</code>, it is
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checked whether the FIFO is bound to the specified
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file system path.</p><p><code class="function">sd_is_socket()</code> may be
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called to check whether the specified file descriptor
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refers to a socket. If the
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<em class="parameter"><code>family</code></em> parameter is not
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<code class="constant">AF_UNSPEC</code>, it is checked whether
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the socket is of the specified family (AF_UNIX,
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<code class="constant">AF_INET</code>, ...). If the
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<em class="parameter"><code>type</code></em> parameter is not 0, it is
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checked whether the socket is of the specified type
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(<code class="constant">SOCK_STREAM</code>,
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<code class="constant">SOCK_DGRAM</code>, ...). If the
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<em class="parameter"><code>listening</code></em> parameter is positive,
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it is checked whether the socket is in accepting mode,
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i.e. <code class="function">listen()</code> has been called for
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it. If <em class="parameter"><code>listening</code></em> is 0, it is
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checked whether the socket is not in this mode. If the
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parameter is negative, no such check is made. The
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<em class="parameter"><code>listening</code></em> parameter should only
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be used for stream sockets and should be set to a
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negative value otherwise.</p><p><code class="function">sd_is_socket_inet()</code> is
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similar to <code class="function">sd_is_socket()</code>, but
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optionally checks the IPv4 or IPv6 port number the
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socket is bound to, unless <em class="parameter"><code>port</code></em>
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is zero. For this call <em class="parameter"><code>family</code></em>
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must be passed as either <code class="constant">AF_UNSPEC</code>, <code class="constant">AF_INET</code>, or
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<code class="constant">AF_INET6</code>.</p><p><code class="function">sd_is_socket_unix()</code> is
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similar to <code class="function">sd_is_socket()</code> but
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optionally checks the <code class="constant">AF_UNIX</code> path the socket is bound
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to, unless the <em class="parameter"><code>path</code></em> parameter
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is <code class="constant">NULL</code>. For normal file system <code class="constant">AF_UNIX</code> sockets,
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set the <em class="parameter"><code>length</code></em> parameter to 0. For
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Linux abstract namespace sockets, set the
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<em class="parameter"><code>length</code></em> to the size of the
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address, including the initial 0 byte, and set the
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<em class="parameter"><code>path</code></em> to the initial 0 byte of
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the socket address.</p><p><code class="function">sd_is_mq()</code> may be called to
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check whether the specified file descriptor refers to
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a POSIX message queue. If the
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<em class="parameter"><code>path</code></em> parameter is not
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<code class="constant">NULL</code>, it is checked whether the
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message queue is bound to the specified name.</p></div><div class="refsect1"><a name="idm274698792912"></a><h2 id="Return Value">Return Value<a class="headerlink" title="Permalink to this headline" href="#Return%20Value">¶</a></h2><p>On failure, these calls return a negative
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errno-style error code. If the file descriptor is of
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the specified type and bound to the specified address,
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a positive return value is returned, otherwise
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zero.</p></div><div class="refsect1"><a name="idm274698791440"></a><h2 id="Notes">Notes<a class="headerlink" title="Permalink to this headline" href="#Notes">¶</a></h2><p>These functions are provided by the reference
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implementation of APIs for new-style daemons and
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distributed with the systemd package. The algorithms
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they implement are simple, and they can easily be
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reimplemented in daemons if it is important to support
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this interface without using the reference
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implementation.</p><p>Internally, these function use a combination of
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<code class="filename">fstat()</code> and
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<code class="filename">getsockname()</code> to check the file
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descriptor type and where it is bound to.</p><p>For details about the algorithms, check the
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liberally licensed reference implementation sources:
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<a class="ulink" href="http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c" target="_top">http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c</a>
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and <a class="ulink" href="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h" target="_top">http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h</a></p><p><code class="function">sd_is_fifo()</code> and the
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related functions are implemented in the reference
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implementation's <code class="filename">sd-daemon.c</code> and
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<code class="filename">sd-daemon.h</code> files. These
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interfaces are available as shared library, which can
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be compiled and linked to with the
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<code class="constant">libsystemd-daemon</code> <a href="pkg-config.html"><span class="citerefentry"><span class="refentrytitle">pkg-config</span>(1)</span></a>
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file. Alternatively, applications consuming these APIs
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may copy the implementation into their source
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tree. For more details about the reference
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implementation see
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<a href="sd-daemon.html"><span class="citerefentry"><span class="refentrytitle">sd-daemon</span>(3)</span></a>.</p><p>These functions continue to work as described,
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even if -DDISABLE_SYSTEMD is set during
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compilation.</p></div><div class="refsect1"><a name="idm274698781152"></a><h2 id="See Also">See Also<a class="headerlink" title="Permalink to this headline" href="#See%20Also">¶</a></h2><p>
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<a href="systemd.html"><span class="citerefentry"><span class="refentrytitle">systemd</span>(1)</span></a>,
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<a href="sd-daemon.html"><span class="citerefentry"><span class="refentrytitle">sd-daemon</span>(3)</span></a>,
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<a href="sd_listen_fds.html"><span class="citerefentry"><span class="refentrytitle">sd_listen_fds</span>(3)</span></a>,
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<a href="systemd.service.html"><span class="citerefentry"><span class="refentrytitle">systemd.service</span>(5)</span></a>,
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<a href="systemd.socket.html"><span class="citerefentry"><span class="refentrytitle">systemd.socket</span>(5)</span></a>
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</p></div></div></body></html>
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