169 lines
5.0 KiB
HTML
169 lines
5.0 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of SD_EVENT_SOURCE_SET_PREPARE</TITLE>
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</HEAD><BODY>
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<H1>SD_EVENT_SOURCE_SET_PREPARE</H1>
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Section: sd_event_source_set_prepare (3)<BR>Updated: <BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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sd_event_source_set_prepare - Set a preparation callback for event sources
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<P>
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<B>
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</B><PRE>
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#include <<A HREF="file:///usr/include/systemd/sd-event.h">systemd/sd-event.h</A>>
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</PRE>
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<DL COMPACT>
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<DT id="1">
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<B>int sd_event_source_set_prepare(sd_event_source *</B><I>source</I><B>, sd_event_handler_t </B><I>callback</I><B>);</B>
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<DT id="2">
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<B>typedef int (*sd_event_handler_t)(sd_event_source *</B><I>s</I><B>, void *</B><I>userdata</I><B>);</B>
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</DL>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<P>
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<B>sd_event_source_set_prepare()</B>
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<DD>may be used to set a preparation callback for the event source object specified as
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<I>source</I>. The callback function specified as
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<I>callback</I>
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will be invoked immediately before the event loop goes to sleep to wait for incoming events. It is invoked with the user data pointer passed when the event source was created. The event source will be disabled if the callback function returns a negative error code. The callback function may be used to reconfigure the precise events to wait for. If the
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<I>callback</I>
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parameter is passed as NULL the callback function is reset.
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<P>
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Event source objects have no preparation callback associated when they are first created with calls such as
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_add_io">sd_event_add_io</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_add_time">sd_event_add_time</A></B>(3). Preparation callback functions are supported for all event source types with the exception of those created with
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_add_exit">sd_event_add_exit</A></B>(3). Preparation callback functions are dispatched in the order indicated by the event source's priority field, as set with
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_source_set_priority">sd_event_source_set_priority</A></B>(3). Preparation callbacks of disabled event sources (see
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_source_set_enabled">sd_event_source_set_enabled</A></B>(3)) are not invoked.
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<A NAME="lbAE"> </A>
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<H2>RETURN VALUE</H2>
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<P>
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On success,
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<B>sd_event_source_set_prepare()</B>
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returns a non-negative integer. On failure, it returns a negative errno-style error code.
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<A NAME="lbAF"> </A>
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<H3>Errors</H3>
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<P>
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Returned errors may indicate the following problems:
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<P>
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<B>-EINVAL</B>
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<DL COMPACT><DT id="3"><DD>
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<I>source</I>
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is not a valid pointer to an
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sd_event_source
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object.
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</DL>
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<P>
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<B>-ESTALE</B>
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<DL COMPACT><DT id="4"><DD>
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The event loop is already terminated.
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</DL>
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<P>
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<B>-ENOMEM</B>
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<DL COMPACT><DT id="5"><DD>
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Not enough memory.
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</DL>
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<P>
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<B>-ECHILD</B>
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<DL COMPACT><DT id="6"><DD>
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The event loop has been created in a different process.
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</DL>
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<P>
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<B>-EDOM</B>
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<DL COMPACT><DT id="7"><DD>
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The specified event source has been created with
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_add_exit">sd_event_add_exit</A></B>(3).
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</DL>
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<A NAME="lbAG"> </A>
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<H2>NOTES</H2>
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<P>
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These APIs are implemented as a shared library, which can be compiled and linked to with the
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<B>libsystemd</B> <B><A HREF="/cgi-bin/man/man2html?1+pkg-config">pkg-config</A></B>(1)
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file.
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<A NAME="lbAH"> </A>
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<H2>SEE ALSO</H2>
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<P>
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<B><A HREF="/cgi-bin/man/man2html?3+sd-event">sd-event</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_add_io">sd_event_add_io</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_add_time">sd_event_add_time</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_add_signal">sd_event_add_signal</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_add_child">sd_event_add_child</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_add_inotify">sd_event_add_inotify</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_add_defer">sd_event_add_defer</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_source_set_enabled">sd_event_source_set_enabled</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_source_set_priority">sd_event_source_set_priority</A></B>(3),
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<B><A HREF="/cgi-bin/man/man2html?3+sd_event_source_set_userdata">sd_event_source_set_userdata</A></B>(3)
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="8"><A HREF="#lbAB">NAME</A><DD>
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<DT id="9"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="10"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="11"><A HREF="#lbAE">RETURN VALUE</A><DD>
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<DL>
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<DT id="12"><A HREF="#lbAF">Errors</A><DD>
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</DL>
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<DT id="13"><A HREF="#lbAG">NOTES</A><DD>
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<DT id="14"><A HREF="#lbAH">SEE ALSO</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:55 GMT, March 31, 2021
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</BODY>
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</HTML>
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