mirror of
https://github.com/morgan9e/systemd
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4a3620c55a
The prohibition to move libsystemd objects between threads was added in64a7ef8bc0('man: be more explicit about thread safety of sd_journal'). At the time, this was valid, because we were using the mempool for allocation and it apparently didn't handle access from different threads. Sadlly, the commit links to a bugzilla entry referenced in the commit is not publicly visible anymore, so the details are murky. But we stopped using the mempool ina5d8835c78('mempool: only enable mempool use when linked to libsystemd-shared.so'), with subsequent followup inb01f31954f('Turn mempool_enabled() into a weak symbol'). The restriction added in the man page is not necessary since then. The text in the man page was arguably incorrect in calling the code "thread-agnostic". If the code does not support being touched from threads at all and has global state to tied to the main thread, it is not "agnostic", but just doesn't support threads. (I'm looking into https://github.com/systemd/python-systemd/issues/143, and with the current scheme, the python-systemd module and all python code using libsystemd would be very hard to use. With the change to free-threaded python in python3.13, i.e. the replacement of single Global Interpreter Lock by locking on individual objects, this limitation would become even more constraining.)
118 lines
4.8 KiB
XML
118 lines
4.8 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_catalog" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_journal_get_catalog</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_catalog</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_catalog</refname>
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<refname>sd_journal_get_catalog_for_message_id</refname>
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<refpurpose>Retrieve message catalog 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_catalog</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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<paramdef>char **<parameter>ret</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_get_catalog_for_message_id</function></funcdef>
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<paramdef>sd_id128_t <parameter>id</parameter></paramdef>
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<paramdef>char **<parameter>ret</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_catalog()</function> retrieves a
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message catalog entry for the current journal entry. This will
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look up an entry in the message catalog by using the
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<literal>MESSAGE_ID=</literal> field of the current journal entry.
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Before returning the entry all journal field names in the catalog
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entry text enclosed in "@" will be replaced by the respective
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field values of the current entry. If a field name referenced in
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the message catalog entry does not exist, in the current journal
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entry, the "@" will be removed, but the field name otherwise left
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untouched.</para>
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<para><function>sd_journal_get_catalog_for_message_id()</function>
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works similar to <function>sd_journal_get_catalog()</function> but
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the entry is looked up by the specified message ID (no open
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journal context is necessary for this), and no field substitution
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is performed.</para>
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<para>For more information about the journal message catalog
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please refer to the <ulink
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url="https://systemd.io/CATALOG">Journal
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Message Catalogs</ulink> documentation page.</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_catalog()</function> and
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<function>sd_journal_get_catalog_for_message_id()</function>
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return 0 on success or a negative errno-style error code. If no
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matching message catalog entry is found, -ENOENT is
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returned.</para>
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<para>On successful return, <parameter>ret</parameter> points to a
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new string, which must be freed with
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<citerefentry project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
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</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>Function <function>sd_journal_get_catalog()</function> is thread-agnostic and only a single thread
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may operate on a given object at any given time. Multiple independent objects may be used from different
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threads in parallel.</para>
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<para>Function <function>sd_journal_get_catalog_for_message_id()</function> is thread-safe and may be
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called from multiple threads in parallel.</para>
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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_catalog()</function> and
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<function>sd_journal_get_catalog_for_message_id()</function> were added in version 196.</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>systemd.journal-fields</refentrytitle><manvolnum>7</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_next</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
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<member><citerefentry project='man-pages'><refentrytitle>malloc</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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