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https://github.com/systemd/systemd-stable.git
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220 lines
11 KiB
XML
220 lines
11 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_is_fifo">
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<refentryinfo>
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<title>sd_is_fifo</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_is_fifo</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_is_fifo</refname>
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<refname>sd_is_socket</refname>
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<refname>sd_is_socket_inet</refname>
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<refname>sd_is_socket_unix</refname>
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<refname>sd_is_mq</refname>
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<refpurpose>Check the type of a file descriptor</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_is_fifo</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>const char *<parameter>path</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_is_socket</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>family</parameter></paramdef>
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<paramdef>int <parameter>type</parameter></paramdef>
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<paramdef>int <parameter>listening</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_is_socket_inet</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>family</parameter></paramdef>
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<paramdef>int <parameter>type</parameter></paramdef>
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<paramdef>int <parameter>listening</parameter></paramdef>
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<paramdef>uint16_t <parameter>port</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_is_socket_unix</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>type</parameter></paramdef>
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<paramdef>int <parameter>listening</parameter></paramdef>
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<paramdef>const char* <parameter>path</parameter></paramdef>
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<paramdef>size_t <parameter>length</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_is_mq</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>const char *<parameter>path</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_is_fifo()</function> 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 <parameter>path</parameter>
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parameter is not <constant>NULL</constant>, it is
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checked whether the FIFO is bound to the specified
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file system path.</para>
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<para><function>sd_is_socket()</function> 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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<parameter>family</parameter> parameter is not
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<constant>AF_UNSPEC</constant>, it is checked whether
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the socket is of the specified family (AF_UNIX,
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<constant>AF_INET</constant>, ...). If the
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<parameter>type</parameter> parameter is not 0, it is
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checked whether the socket is of the specified type
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(<constant>SOCK_STREAM</constant>,
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<constant>SOCK_DGRAM</constant>, ...). If the
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<parameter>listening</parameter> parameter is positive,
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it is checked whether the socket is in accepting mode,
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i.e. <function>listen()</function> has been called for
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it. If <parameter>listening</parameter> 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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<parameter>listening</parameter> 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.</para>
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<para><function>sd_is_socket_inet()</function> is
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similar to <function>sd_is_socket()</function>, but
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optionally checks the IPv4 or IPv6 port number the
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socket is bound to, unless <parameter>port</parameter>
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is zero. For this call <parameter>family</parameter>
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must be passed as either <constant>AF_UNSPEC</constant>, <constant>AF_INET</constant>, or
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<constant>AF_INET6</constant>.</para>
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<para><function>sd_is_socket_unix()</function> is
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similar to <function>sd_is_socket()</function> but
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optionally checks the <constant>AF_UNIX</constant> path the socket is bound
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to, unless the <parameter>path</parameter> parameter
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is <constant>NULL</constant>. For normal file system <constant>AF_UNIX</constant> sockets,
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set the <parameter>length</parameter> parameter to 0. For
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Linux abstract namespace sockets, set the
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<parameter>length</parameter> to the size of the
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address, including the initial 0 byte, and set the
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<parameter>path</parameter> to the initial 0 byte of
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the socket address.</para>
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<para><function>sd_is_mq()</function> 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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<parameter>path</parameter> parameter is not
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<constant>NULL</constant>, it is checked whether the
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message queue is bound to the specified name.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>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.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>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.</para>
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<para>Internally, these function use a combination of
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<filename>fstat()</filename> and
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<filename>getsockname()</filename> to check the file
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descriptor type and where it is bound to.</para>
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<para>For details about the algorithms, check the
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liberally licensed reference implementation sources:
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<ulink url="http://cgit.freedesktop.org/systemd/systemd/plain/src/libsystemd-daemon/sd-daemon.c"/>
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and <ulink
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url="http://cgit.freedesktop.org/systemd/systemd/plain/src/systemd/sd-daemon.h"/></para>
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<para><function>sd_is_fifo()</function> and the
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related functions are implemented in the reference
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implementation's <filename>sd-daemon.c</filename> and
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<filename>sd-daemon.h</filename> 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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<constant>libsystemd-daemon</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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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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<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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<para>These functions continue to work as described,
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even if -DDISABLE_SYSTEMD is set during
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compilation.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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