<?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>