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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
<refentry id="sd_journal_get_cursor" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_journal_get_cursor</title>
<productname>systemd</productname>
</refentryinfo>
<refmeta>
<refentrytitle>sd_journal_get_cursor</refentrytitle>
<manvolnum>3</manvolnum>
</refmeta>
<refnamediv>
<refname>sd_journal_get_cursor</refname>
<refname>sd_journal_test_cursor</refname>
<refpurpose>Get cursor string for or test cursor string against the current journal entry</refpurpose>
</refnamediv>
<refsynopsisdiv>
<funcsynopsis>
<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_journal_get_cursor</function></funcdef>
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
<paramdef>char **<parameter>ret_cursor</parameter></paramdef>
</funcprototype>
<funcprototype>
<funcdef>int <function>sd_journal_test_cursor</function></funcdef>
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
<paramdef>const char *<parameter>cursor</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1>
<title>Description</title>
<para><function>sd_journal_get_cursor()</function> returns a cursor string for the current journal
entry. A cursor is a serialization of the current journal position formatted as text. The string only
contains printable characters and can be passed around in text form. The cursor identifies a journal
entry globally and in a stable way and may be used to later seek to it via
<citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
The cursor string should be considered opaque and not be parsed by clients. Seeking to a cursor position
without the specific entry being available locally will seek to the next closest (in terms of time)
available entry. The call takes two arguments: a journal context object and a pointer to a string pointer
where the cursor string will be placed. The string is allocated via libc <citerefentry
project='man-pages'><refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
should be freed after use with <citerefentry
project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The
<parameter>ret_cursor</parameter> parameter may be passed as <constant>NULL</constant> in which case the
cursor string is not generated, however the return value will indicate whether the journal context is
currently positioned on an entry, and thus has a cursor associated.</para>
<para><function>sd_journal_test_cursor()</function>
may be used to check whether the current position in
the journal matches the specified cursor. This is
useful since cursor strings do not uniquely identify
an entry: the same entry might be referred to by
multiple different cursor strings, and hence string
comparing cursors is not possible. Use this call to
verify after an invocation of
<citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
whether the entry being sought to was actually found
in the journal or the next closest entry was used
instead.</para>
<para>Note that <function>sd_journal_get_cursor()</function>
and <function>sd_journal_test_cursor()</function>
will not work before
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
(or one of the other functions which move to an entry)
has been called at least once to position the read pointer at a valid entry.</para>
</refsect1>
<refsect1>
<title>Return Value</title>
<para><function>sd_journal_get_cursor()</function> returns 0 on
success or a negative errno-style error code.
<function>sd_journal_test_cursor()</function> returns positive if
the current entry matches the specified cursor, 0 if it does not
match the specified cursor or a negative errno-style error code on
failure.</para>
<refsect2>
<title>Errors</title>
<para>Returned errors may indicate the following problems:</para>
<variablelist>
<varlistentry>
<term><constant>-EADDRNOTAVAIL</constant></term>
<listitem><para>The journal context is currently not positioned on any entry, and hence no cursor
string can be generated.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-EINVAL</constant></term>
<listitem><para>The journal context parameter is <constant>NULL</constant>.</para></listitem>
</varlistentry>
<varlistentry>
<term><constant>-ECHILD</constant></term>
<listitem><para>The journal context object has been allocated in a different process than it is
being used in now.</para></listitem>
</varlistentry>
</variablelist>
</refsect2>
</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>History</title>
<para><function>sd_journal_get_cursor()</function> was added in version 187.</para>
<para><function>sd_journal_test_cursor()</function> was added in version 195.</para>
</refsect1>
<refsect1>
<title>See Also</title>
<para><simplelist type="inline">
<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
<member><citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
</simplelist></para>
</refsect1>
</refentry>
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