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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
- "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
This file is part of systemd.
-->
<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>
+ 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