<?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"> <!-- This file is part of systemd. Copyright 2012 Lennart Poettering systemd is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. systemd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with systemd; If not, see <http://www.gnu.org/licenses/>. --> <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 <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>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>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>