Systemd/man/sd-daemon.xml

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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">

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<refentry id="sd-daemon">

        <refentryinfo>
                <title>sd-daemon</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-daemon</refentrytitle>
                <manvolnum>3</manvolnum>
        </refmeta>

        <refnamediv>
                <refname>sd-daemon</refname>
                <refname>SD_EMERG</refname>
                <refname>SD_ALERT</refname>
                <refname>SD_CRIT</refname>
                <refname>SD_ERR</refname>
                <refname>SD_WARNING</refname>
                <refname>SD_NOTICE</refname>
                <refname>SD_INFO</refname>
                <refname>SD_DEBUG</refname>
                <refpurpose>APIs for
                new-style daemons</refpurpose>
        </refnamediv>

        <refsynopsisdiv>
                <funcsynopsis>
                        <funcsynopsisinfo>#include &lt;systemd/sd-daemon.h&gt;</funcsynopsisinfo>
                </funcsynopsis>

                <cmdsynopsis>
                        <command>pkg-config --cflags --libs libsystemd</command>
                </cmdsynopsis>

        </refsynopsisdiv>

        <refsect1>
                <title>Description</title>

                <para><filename>sd-daemon.h</filename> provide APIs
                for new-style daemons, as implemented by the
                <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                init system.</para>

                <para>See
                <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                <citerefentry><refentrytitle>sd_watchdog_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>
                for more information about the functions
                implemented. In addition to these functions, a couple
                of logging prefixes are defined as macros:</para>

                <programlisting>#define SD_EMERG   "&lt;0&gt;"  /* system is unusable */
#define SD_ALERT   "&lt;1&gt;"  /* action must be taken immediately */
#define SD_CRIT    "&lt;2&gt;"  /* critical conditions */
#define SD_ERR     "&lt;3&gt;"  /* error conditions */
#define SD_WARNING "&lt;4&gt;"  /* warning conditions */
#define SD_NOTICE  "&lt;5&gt;"  /* normal but significant condition */
#define SD_INFO    "&lt;6&gt;"  /* informational */
#define SD_DEBUG   "&lt;7&gt;"  /* debug-level messages */</programlisting>

                <para>These prefixes are intended to be used in
                conjunction with stderr-based logging as implemented
                by systemd. If a systemd service definition file is
                configured with <varname>StandardError=syslog</varname>
                or <varname>StandardError=kmsg</varname>, these
                prefixes can be used to encode a log level in lines
                printed. This is similar to the kernel
                <function>printk()</function>-style logging. See
                <citerefentry><refentrytitle>klogctl</refentrytitle><manvolnum>2</manvolnum></citerefentry>
                for more information.</para>

                <para>The log levels are identical to
                <citerefentry><refentrytitle>syslog</refentrytitle><manvolnum>3</manvolnum></citerefentry>'s
                log level system. To use these prefixes simply prefix
                every line with one of these strings. A line that is
                not prefixed will be logged at the default log level
                SD_INFO.</para>

                <example>
                        <title>Hello World</title>

                        <para>A daemon may log with the log level
                        NOTICE by issuing this call:</para>

                        <programlisting>fprintf(stderr, SD_NOTICE "Hello World!\n");</programlisting>
                </example>
        </refsect1>

        <refsect1>
                <title>Notes</title>

                <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>
        </refsect1>

        <refsect1>
                <title>See Also</title>
                <para>
                        <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_notify</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_booted</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_is_fifo</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd_watchdog_enabled</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>,
                        <citerefentry><refentrytitle>fprintf</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>sd-readahead</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
                        <citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
                </para>
        </refsect1>

</refentry>