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234N/A<refentry id="sd_event_add_signal" conditional="ENABLE_KDBUS">

234N/A

234N/A <refentryinfo>

234N/A <title>sd_event_add_signal</title>

234N/A <productname>systemd</productname>

618N/A

234N/A <authorgroup>

234N/A <author>

844N/A <contrib>More text</contrib>

844N/A <firstname>Zbigniew</firstname>

234N/A <surname>Jędrzejewski-Szmek</surname>

1258N/A <email>zbyszek@in.waw.pl</email>

234N/A </author>

234N/A </authorgroup>

234N/A </refentryinfo>

234N/A

234N/A <refmeta>

234N/A <refentrytitle>sd_event_add_signal</refentrytitle>

234N/A <manvolnum>3</manvolnum>

234N/A </refmeta>

234N/A

234N/A <refnamediv>

234N/A <refname>sd_event_add_signal</refname>

234N/A <refname>sd_event_source_get_signal</refname>

234N/A

234N/A <refpurpose>Add a signal event source to an event loop</refpurpose>

234N/A </refnamediv>

234N/A

234N/A <refsynopsisdiv>

234N/A <funcsynopsis>

<funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

<funcprototype>

<funcdef>int <function>sd_event_add_signal</function></funcdef>

<paramdef>sd_event *<parameter>event</parameter></paramdef>

<paramdef>sd_event_source **<parameter>source</parameter></paramdef>

<paramdef>int <parameter>signal</parameter></paramdef>

<paramdef>sd_event_signal_handler_t <parameter>handler</parameter></paramdef>

<paramdef>void *<parameter>userdata</parameter></paramdef>

</funcprototype>

<funcprototype>

<funcdef>typedef int (*<function>sd_event_signal_handler_t</function>)</funcdef>

<paramdef>sd_event_source *<parameter>s</parameter></paramdef>

<paramdef>const struct signalfd_siginfo *<parameter>si</parameter></paramdef>

<paramdef>void *<parameter>userdata</parameter></paramdef>

</funcprototype>

<funcprototype>

<funcdef>int <function>sd_event_source_get_signal</function></funcdef>

<paramdef>sd_event_source *<parameter>source</parameter></paramdef>

</funcprototype>

</funcsynopsis>

</refsynopsisdiv>

<refsect1>

<title>Description</title>

<para><function>sd_event_add_signal()</function> adds a new signal

event source to an event loop object. The event loop is specified

in <parameter>event</parameter>, the event source is returned in

the <parameter>source</parameter> parameter. The

<parameter>signal</parameter> parameter specifies the signal to be handled

(see

<citerefentry project='man-pages'><refentrytitle>signal</refentrytitle><manvolnum>7</manvolnum></citerefentry>).

The <parameter>handler</parameter> must reference a function to

call when the signal is delivered or be <constant>NULL</constant>.

The handler function will be passed the

<parameter>userdata</parameter> pointer, which may be chosen

freely by the caller. The handler also receives a pointer to a

<structname>const struct signalfd_siginfo</structname> containing

the information about the received signal. See

<citerefentry project='man-pages'><refentrytitle>signalfd</refentrytitle><manvolnum>2</manvolnum></citerefentry>

for further information.</para>

<para>Only a single handler may be installed for a specific

signal. The signal will be unblocked, and must be

blocked when the function is called. If the handler is not

specified (<parameter>handler</parameter> is

<constant>NULL</constant>), a default handler which causes the

program to exit will be used. By default, the handler is enabled

permanently (<constant>SD_EVENT_ON</constant>), but this may be

changed with

<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>.

If the handler function returns a negative error code, it will be

disabled after the invocation, even if

<constant>SD_EVENT_ON</constant> mode is set.

</para>

<para><function>sd_event_source_get_signal()</function> retrieves

the configured signal number of a signal event source created

previously with <function>sd_event_add_signal()</function>. It

takes the event source object as the <parameter>source</parameter>

parameter.</para>

</refsect1>

<refsect1>

<title>Return Value</title>

<para>On success, these functions return 0 or a positive

integer. On failure, they return a negative errno-style error

code. </para>

</refsect1>

<refsect1>

<title>Errors</title>

<para>Returned errors may indicate the following problems:</para>

<variablelist>

<varlistentry>

<term><constant>-ENOMEM</constant></term>

<listitem><para>Not enough memory to allocate an object.</para></listitem>

</varlistentry>

<varlistentry>

<term><constant>-EINVAL</constant></term>

<listitem><para>An invalid argument has been passed.</para></listitem>

</varlistentry>

<varlistentry>

<term><constant>-EBUSY</constant></term>

<listitem><para>An handler is already installed for this

signal or the signal was not blocked previously.</para></listitem>

</varlistentry>

<varlistentry>

<term><constant>-ESTALE</constant></term>

<listitem><para>The event loop is already terminated.</para></listitem>

</varlistentry>

<varlistentry>

<term><constant>-ECHILD</constant></term>

<listitem><para>The event loop has been created in a different process.</para></listitem>

</varlistentry>

</variablelist>

</refsect1>

<refsect1>

<title>Notes</title>

<para><function>sd_event_add_signal()</function> and the other functions

described here are available as a shared library, which can be

compiled and linked to with the

<constant>libsystemd</constant> <citerefentry project='die-net'><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-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_event_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

<citerefentry><refentrytitle>sd_event_source_set_enabled</refentrytitle><manvolnum>3</manvolnum></citerefentry>

</para>

</refsect1>

</refentry>