mirror of
https://github.com/systemd/systemd
synced 2024-09-06 08:46:19 +00:00
![Zbigniew Jędrzejewski-Szmek](/assets/img/avatar_default.png)
This way it's much easier to test that the code compiles without issues. It's also easier to edit the code. Indentation in one of the examples is reduced to two spaces. This is what we use in man pages to make them fit on screen better.
149 lines
5.9 KiB
XML
149 lines
5.9 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
|
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
|
|
|
|
<refentry id="sd_journal_next" xmlns:xi="http://www.w3.org/2001/XInclude">
|
|
|
|
<refentryinfo>
|
|
<title>sd_journal_next</title>
|
|
<productname>systemd</productname>
|
|
</refentryinfo>
|
|
|
|
<refmeta>
|
|
<refentrytitle>sd_journal_next</refentrytitle>
|
|
<manvolnum>3</manvolnum>
|
|
</refmeta>
|
|
|
|
<refnamediv>
|
|
<refname>sd_journal_next</refname>
|
|
<refname>sd_journal_previous</refname>
|
|
<refname>sd_journal_next_skip</refname>
|
|
<refname>sd_journal_previous_skip</refname>
|
|
<refname>SD_JOURNAL_FOREACH</refname>
|
|
<refname>SD_JOURNAL_FOREACH_BACKWARDS</refname>
|
|
<refpurpose>Advance or set back the read pointer in the journal</refpurpose>
|
|
</refnamediv>
|
|
|
|
<refsynopsisdiv>
|
|
<funcsynopsis>
|
|
<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_journal_next</function></funcdef>
|
|
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_journal_previous</function></funcdef>
|
|
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_journal_next_skip</function></funcdef>
|
|
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>skip</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef>int <function>sd_journal_previous_skip</function></funcdef>
|
|
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
|
<paramdef>uint64_t <parameter>skip</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef><function>SD_JOURNAL_FOREACH</function></funcdef>
|
|
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
|
</funcprototype>
|
|
|
|
<funcprototype>
|
|
<funcdef><function>SD_JOURNAL_FOREACH_BACKWARDS</function></funcdef>
|
|
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
|
|
</funcprototype>
|
|
</funcsynopsis>
|
|
</refsynopsisdiv>
|
|
|
|
<refsect1>
|
|
<title>Description</title>
|
|
|
|
<para><function>sd_journal_next()</function> advances the read
|
|
pointer into the journal by one entry. The only argument taken is
|
|
a journal context object as allocated via
|
|
<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
|
|
After successful invocation the entry may be read with functions
|
|
such as
|
|
<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
|
|
|
|
<para>Similarly, <function>sd_journal_previous()</function> sets
|
|
the read pointer back one entry.</para>
|
|
|
|
<para><function>sd_journal_next_skip()</function> and
|
|
<function>sd_journal_previous_skip()</function> advance/set back the read pointer by multiple
|
|
entries at once, as specified in the <varname>skip</varname> parameter. The <varname>skip</varname>
|
|
parameter must be less than or equal to 2147483647 (2³¹-1).</para>
|
|
|
|
<para>The journal is strictly ordered by reception time, and hence
|
|
advancing to the next entry guarantees that the entry then
|
|
pointing to is later in time than then previous one, or has the
|
|
same timestamp.</para>
|
|
|
|
<para>Note that
|
|
<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
and related calls will fail unless
|
|
<function>sd_journal_next()</function> has been invoked at least
|
|
once in order to position the read pointer on a journal
|
|
entry.</para>
|
|
|
|
<para>Note that the <function>SD_JOURNAL_FOREACH()</function>
|
|
macro may be used as a wrapper around
|
|
<citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
and <function>sd_journal_next()</function> in order to make
|
|
iterating through the journal easier. See below for an example.
|
|
Similarly, <function>SD_JOURNAL_FOREACH_BACKWARDS()</function> may
|
|
be used for iterating the journal in reverse order.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Return Value</title>
|
|
|
|
<para>The four calls return the number of entries advanced/set
|
|
back on success or a negative errno-style error code. When the end
|
|
or beginning of the journal is reached, a number smaller than
|
|
requested is returned. More specifically, if
|
|
<function>sd_journal_next()</function> or
|
|
<function>sd_journal_previous()</function> reach the end/beginning
|
|
of the journal they will return 0, instead of 1 when they are
|
|
successful. This should be considered an EOF marker.</para>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Notes</title>
|
|
|
|
<xi:include href="threads-aware.xml" xpointer="strict"/>
|
|
|
|
<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>Examples</title>
|
|
|
|
<para>Iterating through the journal:</para>
|
|
|
|
<programlisting><xi:include href="journal-iterate-foreach.c" parse="text" /></programlisting>
|
|
</refsect1>
|
|
|
|
<refsect1>
|
|
<title>See Also</title>
|
|
|
|
<para>
|
|
<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
|
|
<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>
|
|
</para>
|
|
</refsect1>
|
|
|
|
</refentry>
|