+++ /dev/null
-<?xml version='1.0'?> <!--*-nxml-*-->
-<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
-
-<!--
- This file is part of systemd.
-
- Copyright 2010 Lennart Poettering
-
- systemd is free software; you can redistribute it and/or modify it
- under the terms of the GNU Lesser General Public License as published by
- the Free Software Foundation; either version 2.1 of the License, or
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- systemd is distributed in the hope that it will be useful, but
- WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
-
- You should have received a copy of the GNU Lesser General Public License
- along with systemd; If not, see <http://www.gnu.org/licenses/>.
--->
-
-<refentry id="sd_listen_fds"
- xmlns:xi="http://www.w3.org/2001/XInclude">
-
- <refentryinfo>
- <title>sd_listen_fds</title>
- <productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
- </refentryinfo>
-
- <refmeta>
- <refentrytitle>sd_listen_fds</refentrytitle>
- <manvolnum>3</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>sd_listen_fds</refname>
- <refname>SD_LISTEN_FDS_START</refname>
- <refpurpose>Check for file descriptors passed by the system manager</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcsynopsisinfo>#include <systemd/sd-daemon.h></funcsynopsisinfo>
-
- <funcsynopsisinfo>#define SD_LISTEN_FDS_START 3</funcsynopsisinfo>
-
- <funcprototype>
- <funcdef>int <function>sd_listen_fds</function></funcdef>
- <paramdef>int <parameter>unset_environment</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <refsect1>
- <title>Description</title>
-
- <para><function>sd_listen_fds()</function> shall be called by a
- daemon to check for file descriptors passed by the init system as
- part of the socket-based activation logic.</para>
-
- <para>If the <parameter>unset_environment</parameter> parameter is
- non-zero, <function>sd_listen_fds()</function> will unset the
- <varname>$LISTEN_FDS</varname> and <varname>$LISTEN_PID</varname>
- environment variables before returning (regardless of whether the
- function call itself succeeded or not). Further calls to
- <function>sd_listen_fds()</function> will then fail, but the
- variables are no longer inherited by child processes.</para>
-
- <para>If a daemon receives more than one file descriptor, they
- will be passed in the same order as configured in the systemd
- socket unit file (see
- <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- for details). Nonetheless, it is recommended to verify the correct
- socket types before using them. To simplify this checking, the
- functions
- <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_is_socket</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_is_socket_inet</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_is_socket_unix</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- are provided. In order to maximize flexibility, it is recommended
- to make these checks as loose as possible without allowing
- incorrect setups. i.e. often, the actual port number a socket is
- bound to matters little for the service to work, hence it should
- not be verified. On the other hand, whether a socket is a datagram
- or stream socket matters a lot for the most common program logics
- and should be checked.</para>
-
- <para>This function call will set the FD_CLOEXEC flag for all
- passed file descriptors to avoid further inheritance to children
- of the calling process.</para>
-
- <para>If multiple socket units activate the same service the order
- of the file descriptors passed to its main process is undefined.
- If additional file descriptors have been passed to the service
- manager using
- <citerefentry><refentrytitle>sd_pid_notify_with_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>'s
- <literal>FDSTORE=1</literal> messages, these file descriptors are
- passed last, in arbitrary order, and with duplicates
- removed.</para>
- </refsect1>
-
- <refsect1>
- <title>Return Value</title>
-
- <para>On failure, this call returns a negative errno-style error
- code. If
- <varname>$LISTEN_FDS</varname>/<varname>$LISTEN_PID</varname> was
- not set or was not correctly set for this daemon and hence no file
- descriptors were received, 0 is returned. Otherwise, the number of
- file descriptors passed is returned. The application may find them
- starting with file descriptor SD_LISTEN_FDS_START, i.e. file
- descriptor 3.</para>
- </refsect1>
-
- <refsect1>
- <title>Notes</title>
-
- <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
-
- <para>Internally, this function checks whether the
- <varname>$LISTEN_PID</varname> environment variable equals the
- daemon PID. If not, it returns immediately. Otherwise, it parses
- the number passed in the <varname>$LISTEN_FDS</varname>
- environment variable, then sets the FD_CLOEXEC flag for the parsed
- number of file descriptors starting from SD_LISTEN_FDS_START.
- Finally, it returns the parsed number.</para>
- </refsect1>
-
- <refsect1>
- <title>Environment</title>
-
- <variablelist class='environment-variables'>
- <varlistentry>
- <term><varname>$LISTEN_PID</varname></term>
- <term><varname>$LISTEN_FDS</varname></term>
-
- <listitem><para>Set by the init system
- for supervised processes that use
- socket-based activation. This
- environment variable specifies the
- data
- <function>sd_listen_fds()</function>
- parses. See above for
- details.</para></listitem>
- </varlistentry>
- </variablelist>
- </refsect1>
-
- <refsect1>
- <title>See Also</title>
-
- <para>
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_is_socket</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_is_socket_inet</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_is_socket_unix</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- </para>
- </refsect1>
-
-</refentry>
~ianmdlvl / elogind.git / blobdiff