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systemd-stable/man/sd_event_source_set_enabled.xml
Zbigniew Jędrzejewski-Szmek 11a1589223 tree-wide: drop license boilerplate
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.

I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
2018-04-06 18:58:55 +02:00

169 lines
6.1 KiB
XML

<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1+
This file is part of systemd.
Copyright 2015 Lennart Poettering
-->
<refentry id="sd_event_source_set_enabled" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_event_source_set_enabled</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_event_source_set_enabled</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_event_source_set_enabled</refname>
<refname>sd_event_source_get_enabled</refname>
<refname>SD_EVENT_ON</refname>
<refname>SD_EVENT_OFF</refname>
<refname>SD_EVENT_ONESHOT</refname>
<refpurpose>Enable or disable event sources</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include &lt;systemd/sd-event.h&gt;</funcsynopsisinfo>
<funcsynopsisinfo><token>enum</token> {
<constant>SD_EVENT_OFF</constant> = 0,
<constant>SD_EVENT_ON</constant> = 1,
<constant>SD_EVENT_ONESHOT</constant> = -1,
};</funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_event_source_set_enabled</function></funcdef>
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
<paramdef>int <parameter>enabled</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_event_source_get_enabled</function></funcdef>
<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
<paramdef>int *<parameter>enabled</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_event_source_set_enabled()</function> may be
used to enable or disable the event source object specified as
<parameter>source</parameter>. The <parameter>enabled</parameter>
parameter takes one of <constant>SD_EVENT_ON</constant> (to
enable), <constant>SD_EVENT_OFF</constant> (to disable) or
<constant>SD_EVENT_ONESHOT</constant>. If invoked with
<constant>SD_EVENT_ONESHOT</constant> the event source will be
enabled but automatically reset to
<constant>SD_EVENT_OFF</constant> after the event source was
dispatched once.</para>
<para>Event sources that are disabled will not result in event
loop wakeups and will not be dispatched, until they are enabled
again.</para>
<para><function>sd_event_source_get_enabled()</function> may be
used to query whether the event source object
<parameter>source</parameter> is currently enabled or not. It
returns the enablement state in
<parameter>enabled</parameter>.</para>
<para>Event source objects are enabled when they are first created
with calls such as
<citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. However,
depending on the event source type they are enabled continuously
(<constant>SD_EVENT_ON</constant>) or only for a single invocation
of the event source handler
(<constant>SD_EVENT_ONESHOT</constant>). For details see the
respective manual pages.</para>
<para>As event source objects stay active and may be dispatched as
long as there is at least one reference to them, in many cases it
is a good idea to combine a call to
<citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
with a prior call to
<function>sd_event_source_set_enabled()</function> with
<constant>SD_EVENT_OFF</constant>, to ensure the event source is
not dispatched again until all other remaining references are dropped.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para>On success, <function>sd_event_source_set_enabled()</function> and
<function>sd_event_source_get_enabled()</function> return a
non-negative 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>-EINVAL</constant></term>
<listitem><para><parameter>source</parameter> is not a valid
pointer to an <structname>sd_event_source</structname>
object.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ENOMEM</constant></term>
<listitem><para>Not enough memory.</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>
<xi:include href="libsystemd-pkgconfig.xml" />
<refsect1>
<title>See Also</title>
<para>
<citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_io</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_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
<citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>