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122 lines
5.1 KiB
XML
122 lines
5.1 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
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<refentry id="sd_journal_get_cursor" xmlns:xi="http://www.w3.org/2001/XInclude">
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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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</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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<refname>sd_journal_test_cursor</refname>
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<refpurpose>Get cursor string for or test cursor string against 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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<funcprototype>
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<funcdef>int <function>sd_journal_test_cursor</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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<paramdef>const 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> returns a
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cursor string for the current journal entry. A cursor is a
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serialization of the current journal position formatted as text.
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The string only contains printable characters and can be passed
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around 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 seek to it
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via
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<citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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The cursor string should be considered opaque and not be parsed by
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clients. Seeking to a cursor position without the specific entry
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being available locally will seek to the next closest (in terms of
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time) available entry. The call takes two arguments: a journal
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context object and a pointer to a string pointer where the cursor
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string will be placed. The string is allocated via libc
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<citerefentry project='man-pages'><refentrytitle>malloc</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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and should be freed after use with
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<citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para>
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<para><function>sd_journal_test_cursor()</function>
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may be used to check whether the current position in
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the journal matches the specified cursor. This is
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useful since cursor strings do not uniquely identify
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an entry: the same entry might be referred to by
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multiple different cursor strings, and hence string
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comparing cursors is not possible. Use this call to
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verify after an invocation of
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<citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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whether the entry being sought to was actually found
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in the journal or the next closest entry was used
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instead.</para>
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<para>Note that <function>sd_journal_get_cursor()</function>
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and <function>sd_journal_test_cursor()</function>
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will not work before
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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(or one of the other functions which move to an entry)
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has been called at least once 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> returns 0 on
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success or a negative errno-style error code.
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<function>sd_journal_test_cursor()</function> returns positive if
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the current entry matches the specified cursor, 0 if it does not
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match the specified cursor or a negative errno-style error code on
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failure.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<xi:include href="threads-aware.xml" xpointer="strict" />
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<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
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</refsect1>
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<refsect1>
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<title>History</title>
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<para><function>sd_journal_get_cursor()</function> was added in version 187.</para>
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<para><function>sd_journal_test_cursor()</function> was added in version 195.</para>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para><simplelist type="inline">
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<member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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</simplelist></para>
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</refsect1>
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</refentry>
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