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/>.
-->
<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 <systemd/sd-daemon.h></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>
+ <para>These APIs are implemented as a shared library,
+ which can be compiled and linked to with the
+ <constant>libsystemd</constant> <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+ file.</para>
<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>
~ianmdlvl / elogind.git / blobdiff