chiark / gitweb /
networkd: support vxlan parameters
[elogind.git] / man / sd_listen_fds.xml
index 10ea57c..6999db9 100644 (file)
@@ -8,20 +8,21 @@
   Copyright 2010 Lennart Poettering
 
   systemd is free software; you can redistribute it and/or modify it
-  under the terms of the GNU General Public License as published by
-  the Free Software Foundation; either version 2 of the License, or
+  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
   (at your option) any later version.
 
   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
-  General Public License for more details.
+  Lesser General Public License for more details.
 
-  You should have received a copy of the GNU General Public License
+  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">
+<refentry id="sd_listen_fds"
+        xmlns:xi="http://www.w3.org/2001/XInclude">
 
         <refentryinfo>
                 <title>sd_listen_fds</title>
 
         <refnamediv>
                 <refname>sd_listen_fds</refname>
-                <refpurpose>Check for file descriptors passed by the init system.</refpurpose>
+                <refname>SD_LISTEN_FDS_START</refname>
+                <refpurpose>Check for file descriptors passed by the system manager</refpurpose>
         </refnamediv>
 
         <refsynopsisdiv>
                 <funcsynopsis>
-                        <funcsynopsisinfo>#include "sd-daemon.h"</funcsynopsisinfo>
+                        <funcsynopsisinfo>#include &lt;systemd/sd-daemon.h&gt;</funcsynopsisinfo>
 
                         <funcsynopsisinfo>#define SD_LISTEN_FDS_START 3</funcsynopsisinfo>
 
                 activation logic.</para>
 
                 <para>If the <parameter>unset_environment</parameter>
-                parameter is non-zero
+                parameter is non-zero,
                 <function>sd_listen_fds()</function> will unset the
                 <varname>$LISTEN_FDS</varname>/<varname>$LISTEN_PID</varname>
-                environment variables before returning (regardless
+                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,
                 <para>If a daemon receives more than one file
                 descriptor, they will be passed in the same order as
                 configured in the systemd socket definition
-                file. Nonetheless it is recommended to verify the
+                file. Nonetheless, it is recommended to verify the
                 correct socket types before using them. To simplify
-                this checking the functions
+                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
-                recommened to make these checks as loose as possible
-                without allowing incorrect setups. i.e. often the
+                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 hence be
-                checked.</para>
+                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
                 <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 not correctly set for this daemon and
-                hence no file descriptors received 0 is
-                returned. Otherwise the number of file descriptors
-                passed is returned, the application may find them
+                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>
 
-                <para>This function is provided by the reference
-                implementation of APIs for new-style daemons and
-                distributed with the systemd package. The algorithm it
-                implements is simple, and can easily be reimplemented
-                in daemons if it is important to support this
-                interface without using the reference
-                implementation.</para>
+                <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
 
                 <para>Internally, this function checks whether the
                 <varname>$LISTEN_PID</varname> environment variable
                 equals the daemon PID. If not, it returns
-                immediately. Otherwise it parses the number passed in
+                immediately. Otherwise, it parses the number passed in
                 the <varname>$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
+                SD_LISTEN_FDS_START. Finally, it returns the parsed
                 number.</para>
+        </refsect1>
 
-                <para>For details about the algorithm check the
-                liberally licensed reference implementation sources:
-                <ulink url="http://cgit.freedesktop.org/systemd/tree/src/sd-daemon.c"/>
-                resp. <ulink
-                url="http://cgit.freedesktop.org/systemd/tree/src/sd-daemon.h"/></para>
-
-                <para><function>sd_listen_fds()</function> is
-                implemented in the reference implementation's drop-in
-                <filename>sd-daemon.c</filename> and
-                <filename>sd-daemon.h</filename> files. It is
-                recommended that applications consuming these APIs
-                copy the implementation into their source tree. For
-                more details about the reference implementation see
-                <citerefentry><refentrytitle>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry></para>
-
-                <para>If -DDISABLE_SYSTEMD is set during compilation
-                this function will always return 0 and otherwise
-                become a NOP.</para>
+        <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>sd_daemon</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+                        <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</refentrytitle><manvolnum>8</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>systemd.service</refentrytitle><manvolnum>5</manvolnum></citerefentry>,
                         <citerefentry><refentrytitle>systemd.socket</refentrytitle><manvolnum>5</manvolnum></citerefentry>
                 </para>