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<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd_event_source_set_description" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_event_source_set_description</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_event_source_set_description</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_event_source_set_description</refname>
<refname>sd_event_source_get_description</refname>
<refpurpose>Set or retrieve descriptive names of event sources</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_event_source_set_description</function></funcdef>
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
<paramdef>const char *<parameter>description</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_event_source_get_description</function></funcdef>
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
<paramdef>const char **<parameter>ret</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_event_source_set_description()</function> may
be used to set an arbitrary descriptive name for the event source
object specified as <parameter>source</parameter>. This name will
be used in debugging messages generated by
<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>
for this event source, and may be queried using
<function>sd_event_source_get_description()</function> for
debugging purposes. The <parameter>description</parameter> parameter shall
point to a <constant>NUL</constant>-terminated string or be
<constant>NULL</constant>. In the latter case, the descriptive
name will be unset. The string is copied internally, hence the
<parameter>description</parameter> argument is not referenced
after the function returns.</para>
<para><function>sd_event_source_get_description()</function> may
be used to query the current descriptive name assigned to the
event source object <parameter>source</parameter>. It returns a
pointer to the current name in <parameter>ret</parameter>,
stored in memory internal to the event source. The memory is
invalidated when the event source is destroyed or the descriptive
name is changed.</para>
<para>Event source objects generally have no description set when
they are created, except for UNIX signal event sources created
with
<citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
whose descriptive name is initialized to the signal's C constant
name (e.g. <literal>SIGINT</literal> or
<literal>SIGTERM</literal>).</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, <function>sd_event_source_set_description()</function> and
<function>sd_event_source_get_description()</function> return a non-negative integer. On failure, they
return a negative errno-style error code.</para>
<refsect2>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para><parameter>source</parameter> is not a valid pointer to an
<structname>sd_event_source</structname> object or the <parameter>description</parameter> argument
for <function>sd_event_source_get_description()</function> is <constant>NULL</constant>.
</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOMEM</constant></term>
<listitem><para>Not enough memory to copy the name.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ECHILD</constant></term>
<listitem><para>The event loop has been created in a different process, library or module instance.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENXIO</constant></term>
<listitem><para>No name was set for the event source.</para></listitem>
</varlistentry>
</variablelist>
</refsect2>
</refsect1>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>History</title>
<para><function>sd_event_source_set_description()</function> and
<function>sd_event_source_get_description()</function> were added in version 229.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para><simplelist type="inline">
<member><citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_event_source_set_userdata</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
</simplelist></para>
</refsect1>
</refentry>
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