man: document sd_journal_get_cursor()
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Lennart Poettering
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@ -505,7 +505,8 @@ MANPAGES = \
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man/sd_journal_next.3 \
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man/sd_journal_get_data.3 \
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man/sd_journal_get_realtime_usec.3 \
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man/sd_journal_get_cutoff_realtime_usec.3
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man/sd_journal_get_cutoff_realtime_usec.3 \
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man/sd_journal_get_cursor.3
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MANPAGES_ALIAS = \
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man/reboot.8 \
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@ -0,0 +1,122 @@
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<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2012 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_journal_get_cursor">
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<refentryinfo>
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<title>sd_journal_get_cursor</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_journal_get_cursor</refentrytitle>
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<manvolnum>3</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>sd_journal_get_cursor</refname>
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<refpurpose>Get cursor string for the current journal entry</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
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<funcprototype>
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<funcdef>int <function>sd_journal_get_cursor</function></funcdef>
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<paramdef>sd_journal* <parameter>j</parameter></paramdef>
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<paramdef>char ** <parameter>cursor</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Description</title>
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<para><function>sd_journal_get_cursor()</function>
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returns a cursor string for the current journal
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entry. A cursor is a serialization of the current
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journal position in text form. The string only
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contains printable characters and can be passed around
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in text form. The cursor identifies a journal entry
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globally and in a stable way and may be used to later
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seek to it via
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<citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. The
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cursor string should be considered opaque and not be
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parsed by clients. Seeking to a cursor position
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without the specific entry being available locally
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will seek to the next closest (in terms of time)
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available entry. The call takes two arguments: a
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journal context object and a pointer to a
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string pointer where the cursor string will be
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placed. The string is allocated via libc <citerefentry><refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum></citerefentry> and should
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be freed after use with
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<citerefentry><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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<para>Note that this function will not work before
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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(or related call) has been called at least
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once, in order to position the read pointer at a valid entry.</para>
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</refsect1>
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<refsect1>
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<title>Return Value</title>
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<para><function>sd_journal_get_cursor()</function>
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returns 0 on success or a negative errno-style error
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code.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>The <function>sd_journal_get_cursor()</function>
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interface is available as shared library, which can be
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compiled and linked to with the
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<literal>libsystemd-journal</literal>
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<citerefentry><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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@ -45,7 +45,7 @@
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<refnamediv>
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<refname>sd_journal_get_cutoff_realtime_usec</refname>
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<refname>sd_journal_get_cutoff_monotonic_usec</refname>
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<refpurpose>Read timestamps from the current journal entry</refpurpose>
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<refpurpose>Read cut-off timestamps from the current journal entry</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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@ -127,7 +127,7 @@
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<para>Note that these functions will not work before
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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(or related call) has been called at least
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once.</para>
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once, in order to position the read pointer at a valid entry.</para>
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</refsect1>
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<refsect1>
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@ -99,7 +99,7 @@
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<para>Note that these functions will not work before
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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(or related call) has been called at least
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once.</para>
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once, in order to position the read pointer at a valid entry.</para>
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</refsect1>
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<refsect1>
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@ -205,7 +205,9 @@ int main(int argc, char *argv[]) {
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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<citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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@ -118,6 +118,25 @@
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for an example how to iterate through the journal
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after opening it it with
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<function>sd_journal_open()</function>.</para>
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<para>A journal context object returned by
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<function>sd_journal_open()</function> references a
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specific journal entry as <emphasis>current</emphasis> entry,
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similar to a file seek index in a classic file system
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file, but without absolute positions. It may be
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altered with
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and
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<citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and related calls. The current entry position may be
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exported in <emphasis>cursor</emphasis> strings, as accessible
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via
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<citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. Cursor
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strings may be used to globally identify a specific
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journal entry in a stable way and then later to seek
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to it (or if the specific entry is not available
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locally, to its closest entry in time)
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<citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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</refsect1>
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<refsect1>
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