1<?xml version='1.0'?> <!--*-nxml-*-->
2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
4<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
5
6<refentry id="sd_journal_get_cursor" xmlns:xi="http://www.w3.org/2001/XInclude">
7
8  <refentryinfo>
9    <title>sd_journal_get_cursor</title>
10    <productname>systemd</productname>
11  </refentryinfo>
12
13  <refmeta>
14    <refentrytitle>sd_journal_get_cursor</refentrytitle>
15    <manvolnum>3</manvolnum>
16  </refmeta>
17
18  <refnamediv>
19    <refname>sd_journal_get_cursor</refname>
20    <refname>sd_journal_test_cursor</refname>
21    <refpurpose>Get cursor string for or test cursor string against the current journal entry</refpurpose>
22  </refnamediv>
23
24  <refsynopsisdiv>
25    <funcsynopsis>
26      <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
27
28      <funcprototype>
29        <funcdef>int <function>sd_journal_get_cursor</function></funcdef>
30        <paramdef>sd_journal *<parameter>j</parameter></paramdef>
31        <paramdef>char **<parameter>cursor</parameter></paramdef>
32      </funcprototype>
33
34      <funcprototype>
35        <funcdef>int <function>sd_journal_test_cursor</function></funcdef>
36        <paramdef>sd_journal *<parameter>j</parameter></paramdef>
37        <paramdef>const char *<parameter>cursor</parameter></paramdef>
38      </funcprototype>
39
40    </funcsynopsis>
41  </refsynopsisdiv>
42
43  <refsect1>
44    <title>Description</title>
45
46    <para><function>sd_journal_get_cursor()</function> returns a
47    cursor string for the current journal entry. A cursor is a
48    serialization of the current journal position formatted as text.
49    The string only contains printable characters and can be passed
50    around in text form. The cursor identifies a journal entry
51    globally and in a stable way and may be used to later seek to it
52    via
53    <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
54    The cursor string should be considered opaque and not be parsed by
55    clients. Seeking to a cursor position without the specific entry
56    being available locally will seek to the next closest (in terms of
57    time) available entry. The call takes two arguments: a journal
58    context object and a pointer to a string pointer where the cursor
59    string will be placed. The string is allocated via libc
60    <citerefentry project='man-pages'><refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum></citerefentry>
61    and should be freed after use with
62    <citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
63
64    <para>Note that <function>sd_journal_get_cursor()</function> will
65    not work before
66    <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
67    (or related call) has been called at least once, in order to
68    position the read pointer at a valid entry.</para>
69
70    <para><function>sd_journal_test_cursor()</function>
71    may be used to check whether the current position in
72    the journal matches the specified cursor. This is
73    useful since cursor strings do not uniquely identify
74    an entry: the same entry might be referred to by
75    multiple different cursor strings, and hence string
76    comparing cursors is not possible. Use this call to
77    verify after an invocation of
78    <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>
79    whether the entry being sought to was actually found
80    in the journal or the next closest entry was used
81    instead.</para>
82  </refsect1>
83
84  <refsect1>
85    <title>Return Value</title>
86
87    <para><function>sd_journal_get_cursor()</function> returns 0 on
88    success or a negative errno-style error code.
89    <function>sd_journal_test_cursor()</function> returns positive if
90    the current entry matches the specified cursor, 0 if it does not
91    match the specified cursor or a negative errno-style error code on
92    failure.</para>
93  </refsect1>
94
95  <refsect1>
96    <title>Notes</title>
97
98    <xi:include href="threads-aware.xml" xpointer="strict" />
99
100    <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
101  </refsect1>
102
103  <refsect1>
104    <title>See Also</title>
105
106    <para>
107      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
108      <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
109      <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
110      <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>
111    </para>
112  </refsect1>
113
114</refentry>
115