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163 lines
7.3 KiB
XML
163 lines
7.3 KiB
XML
<?xml version='1.0'?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_event_source_set_enabled" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_event_source_set_enabled</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_event_source_set_enabled</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_event_source_set_enabled</refname>
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<refname>sd_event_source_get_enabled</refname>
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<refname>SD_EVENT_ON</refname>
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<refname>SD_EVENT_OFF</refname>
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<refname>SD_EVENT_ONESHOT</refname>
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<refpurpose>Enable or disable event sources</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-event.h></funcsynopsisinfo>
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<funcsynopsisinfo><token>enum</token> {
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<constant>SD_EVENT_OFF</constant> = 0,
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<constant>SD_EVENT_ON</constant> = 1,
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<constant>SD_EVENT_ONESHOT</constant> = -1,
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};</funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_event_source_set_enabled</function></funcdef>
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<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
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<paramdef>int <parameter>enabled</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_event_source_get_enabled</function></funcdef>
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<paramdef>sd_event_source *<parameter>source</parameter></paramdef>
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<paramdef>int *<parameter>ret</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_event_source_set_enabled()</function> may be used to enable or disable the event
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source object specified as <parameter>source</parameter>. The <parameter>enabled</parameter> parameter
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takes one of <constant>SD_EVENT_ON</constant> (to enable), <constant>SD_EVENT_OFF</constant> (to disable)
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or <constant>SD_EVENT_ONESHOT</constant>. If invoked with <constant>SD_EVENT_ONESHOT</constant> the event
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source will be enabled but automatically reset to <constant>SD_EVENT_OFF</constant> after one dispatch.
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For <constant>SD_EVENT_OFF</constant>, the event source <parameter>source</parameter> may be
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<constant>NULL</constant>, in which case the function does nothing. Otherwise,
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<parameter>source</parameter> must be a valid pointer to an <structname>sd_event_source</structname>
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object.</para>
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<para>Event sources that are disabled will not result in event
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loop wakeups and will not be dispatched, until they are enabled
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again.</para>
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<para><function>sd_event_source_get_enabled()</function> may be used to query whether the event source
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object <parameter>source</parameter> is currently enabled or not. If both the
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<parameter>source</parameter> and the output parameter <parameter>ret</parameter> are
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<constant>NULL</constant>, this function returns false. Otherwise, <parameter>source</parameter> must be
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a valid pointer to an <structname>sd_event_source</structname> object. If the output parameter
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<parameter>ret</parameter> is not <constant>NULL</constant>, it is set to the enablement state (one
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of <constant>SD_EVENT_ON</constant>, <constant>SD_EVENT_OFF</constant>,
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<constant>SD_EVENT_ONESHOT</constant>). The function also returns true if the event source is not
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disabled.</para>
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<para>Event source objects are enabled when they are first created
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with calls such as
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<citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry>. However,
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depending on the event source type they are enabled continuously
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(<constant>SD_EVENT_ON</constant>) or only for a single invocation
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of the event source handler
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(<constant>SD_EVENT_ONESHOT</constant>). For details see the
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respective manual pages.</para>
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<para>As event source objects stay active and may be dispatched as
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long as there is at least one reference to them, in many cases it
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is a good idea to combine a call to
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<citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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with a prior call to
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<function>sd_event_source_set_enabled()</function> with
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<constant>SD_EVENT_OFF</constant>, to ensure the event source is
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not dispatched again until all other remaining references are dropped.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para>On success, <function>sd_event_source_set_enabled()</function> returns a non-negative
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integer. <function>sd_event_source_get_enabled()</function> returns zero if the source is disabled
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(<constant>SD_EVENT_OFF</constant>) and a positive integer otherwise. On failure, they return a negative
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errno-style error code.</para>
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<refsect2>
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<title>Errors</title>
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<para>Returned errors may indicate the following problems:</para>
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<variablelist>
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<varlistentry>
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<term><constant>-EINVAL</constant></term>
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<listitem><para><parameter>source</parameter> is not a valid pointer to an
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<structname>sd_event_source</structname> object.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ENOMEM</constant></term>
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<listitem><para>Not enough memory.</para></listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>-ECHILD</constant></term>
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<listitem><para>The event loop has been created in a different process, library or module instance.</para></listitem>
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</varlistentry>
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</variablelist>
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</refsect2>
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</refsect1>
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<xi:include href="libsystemd-pkgconfig.xml" />
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<refsect1>
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<title>History</title>
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<para><function>sd_event_source_set_enabled()</function> and
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<function>sd_event_source_get_enabled()</function> were added in version 229.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_event_add_io</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_event_add_time</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_event_add_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_event_add_child</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_event_add_inotify</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_event_add_defer</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_event_source_unref</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_event_source_set_ratelimit</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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