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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"

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<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>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>