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systemd/man/sd_journal_get_cursor.xml
Zbigniew Jędrzejewski-Szmek 11a1589223 tree-wide: drop license boilerplate
Files which are installed as-is (any .service and other unit files, .conf
files, .policy files, etc), are left as is. My assumption is that SPDX
identifiers are not yet that well known, so it's better to retain the
extended header to avoid any doubt.

I also kept any copyright lines. We can probably remove them, but it'd nice to
obtain explicit acks from all involved authors before doing that.
2018-04-06 18:58:55 +02:00

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<?xml version='1.0'?> <!--*-nxml-*-->
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
<!--
SPDX-License-Identifier: LGPL-2.1+
This file is part of systemd.
Copyright 2012 Lennart Poettering
-->
<refentry id="sd_journal_get_cursor">
<refentryinfo>
<title>sd_journal_get_cursor</title>
<productname>systemd</productname>
<authorgroup>
<author>
<contrib>Developer</contrib>
<firstname>Lennart</firstname>
<surname>Poettering</surname>
<email>lennart@poettering.net</email>
</author>
</authorgroup>
</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 &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
<funcprototype>
<funcdef>int <function>sd_journal_get_cursor</function></funcdef>
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
<paramdef>char **<parameter>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>.</para>
<para>Note that <function>sd_journal_get_cursor()</function> will
not work before
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
(or related call) has been called at least once, in order to
position the read pointer at a valid entry.</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>
</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>
</refsect1>
<refsect1>
<title>Notes</title>
<para>All functions listed here are thread-agnostic and only a single thread may operate
on a given <structname>sd_journal</structname> object.</para>
<para>The <function>sd_journal_get_cursor()</function> and
<function>sd_journal_test_cursor()</function> interfaces are
available as a shared library, which can be compiled and linked to
with the
<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
file.</para>
</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_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>
</para>
</refsect1>
</refentry>