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- Copyright 2012 Lennart Poettering
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<refentry id="sd_journal_get_fd" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_journal_get_fd</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
immediately for all journal changes. Returns 0 if there might be a
latency involved.</para>
- <para><function>sd_journal_process()</function> and
- <function>sd_journal_wait()</function> return one of
- <constant>SD_JOURNAL_NOP</constant>,
- <constant>SD_JOURNAL_APPEND</constant> or
- <constant>SD_JOURNAL_INVALIDATE</constant> on success or a
- negative errno-style error code. If
- <constant>SD_JOURNAL_NOP</constant> is returned, the journal did
- not change since the last invocation. If
- <constant>SD_JOURNAL_APPEND</constant> is returned, new entries
- have been appended to the end of the journal. If
- <constant>SD_JOURNAL_INVALIDATE</constant>, journal files were
- added or removed (possibly due to rotation). In the latter event,
- live-view UIs should probably refresh their entire display, while
- in the case of <constant>SD_JOURNAL_APPEND</constant>, it is
- sufficient to simply continue reading at the previous end of the
- journal.</para>
+ <para><function>sd_journal_process()</function> and <function>sd_journal_wait()</function> return a negative
+ errno-style error code, or one of <constant>SD_JOURNAL_NOP</constant>, <constant>SD_JOURNAL_APPEND</constant> or
+ <constant>SD_JOURNAL_INVALIDATE</constant> on success:</para>
+
+ <itemizedlist>
+ <listitem><para>If <constant>SD_JOURNAL_NOP</constant> is returned, the journal did not change since the last
+ invocation.</para></listitem>
+
+ <listitem><para>If <constant>SD_JOURNAL_APPEND</constant> is returned, new entries have been appended to the end
+ of the journal. In this case it is sufficient to simply continue reading at the previous end location of the
+ journal, to read the newly added entries.</para></listitem>
+
+ <listitem><para>If <constant>SD_JOURNAL_INVALIDATE</constant>, journal files were added to or removed from the
+ set of journal files watched (e.g. due to rotation or vacuuming), and thus entries might have appeared or
+ disappeared at arbitrary places in the log stream, possibly before or after the previous end of the log
+ stream. If <constant>SD_JOURNAL_INVALIDATE</constant> is returned, live-view UIs that want to reflect on screen
+ the precise state of the log data on disk should probably refresh their entire display (relative to the cursor of
+ the log entry on the top of the screen). Programs only interested in a strictly sequential stream of log data may
+ treat <constant>SD_JOURNAL_INVALIDATE</constant> the same way as <constant>SD_JOURNAL_APPEND</constant>, thus
+ ignoring any changes to the log view earlier than the old end of the log stream.</para></listitem>
+ </itemizedlist>
</refsect1>
<refsect1>