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Diffstat (limited to 'src/libsystemd/sd_journal_open.xml')
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diff --git a/src/libsystemd/sd_journal_open.xml b/src/libsystemd/sd_journal_open.xml new file mode 100644 index 0000000000..25b3048f2e --- /dev/null +++ b/src/libsystemd/sd_journal_open.xml @@ -0,0 +1,234 @@ +<?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_open"> + + <refentryinfo> + <title>sd_journal_open</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_open</refentrytitle> + <manvolnum>3</manvolnum> + </refmeta> + + <refnamediv> + <refname>sd_journal_open</refname> + <refname>sd_journal_open_directory</refname> + <refname>sd_journal_open_directory_fd</refname> + <refname>sd_journal_open_files</refname> + <refname>sd_journal_open_files_fd</refname> + <refname>sd_journal_close</refname> + <refname>sd_journal</refname> + <refname>SD_JOURNAL_LOCAL_ONLY</refname> + <refname>SD_JOURNAL_RUNTIME_ONLY</refname> + <refname>SD_JOURNAL_SYSTEM</refname> + <refname>SD_JOURNAL_CURRENT_USER</refname> + <refname>SD_JOURNAL_OS_ROOT</refname> + <refpurpose>Open the system journal for reading</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> + + <funcprototype> + <funcdef>int <function>sd_journal_open</function></funcdef> + <paramdef>sd_journal **<parameter>ret</parameter></paramdef> + <paramdef>int <parameter>flags</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_journal_open_directory</function></funcdef> + <paramdef>sd_journal **<parameter>ret</parameter></paramdef> + <paramdef>const char *<parameter>path</parameter></paramdef> + <paramdef>int <parameter>flags</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_journal_open_directory_fd</function></funcdef> + <paramdef>sd_journal **<parameter>ret</parameter></paramdef> + <paramdef>int <parameter>fd</parameter></paramdef> + <paramdef>int <parameter>flags</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_journal_open_files</function></funcdef> + <paramdef>sd_journal **<parameter>ret</parameter></paramdef> + <paramdef>const char **<parameter>paths</parameter></paramdef> + <paramdef>int <parameter>flags</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_journal_open_files_fd</function></funcdef> + <paramdef>sd_journal **<parameter>ret</parameter></paramdef> + <paramdef>int <parameter>fds[]</parameter></paramdef> + <paramdef>unsigned <parameter>n_fds</parameter></paramdef> + <paramdef>int <parameter>flags</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>void <function>sd_journal_close</function></funcdef> + <paramdef>sd_journal *<parameter>j</parameter></paramdef> + </funcprototype> + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><function>sd_journal_open()</function> opens the log journal + for reading. It will find all journal files automatically and + interleave them automatically when reading. As first argument it + takes a pointer to a <varname>sd_journal</varname> pointer, which, + on success, will contain a journal context object. The second + argument is a flags field, which may consist of the following + flags ORed together: <constant>SD_JOURNAL_LOCAL_ONLY</constant> + makes sure only journal files generated on the local machine will + be opened. <constant>SD_JOURNAL_RUNTIME_ONLY</constant> makes sure + only volatile journal files will be opened, excluding those which + are stored on persistent storage. + <constant>SD_JOURNAL_SYSTEM</constant> will cause journal files of + system services and the kernel (in opposition to user session + processes) to be opened. + <constant>SD_JOURNAL_CURRENT_USER</constant> will cause journal + files of the current user to be opened. If neither + <constant>SD_JOURNAL_SYSTEM</constant> nor + <constant>SD_JOURNAL_CURRENT_USER</constant> are specified, all + journal file types will be opened.</para> + + <para><function>sd_journal_open_directory()</function> is similar to <function>sd_journal_open()</function> but + takes an absolute directory path as argument. All journal files in this directory will be opened and interleaved + automatically. This call also takes a flags argument. The flags parameters accepted by this call are + <constant>SD_JOURNAL_OS_ROOT</constant>, <constant>SD_JOURNAL_SYSTEM</constant>, and + <constant>SD_JOURNAL_CURRENT_USER</constant>. If <constant>SD_JOURNAL_OS_ROOT</constant> is specified, journal + files are searched for below the usual <filename>/var/log/journal</filename> and + <filename>/run/log/journal</filename> relative to the specified path, instead of directly beneath it. + The other two flags limit which files are opened, the same as for <function>sd_journal_open()</function>. + </para> + + <para><function>sd_journal_open_directory_fd()</function> is similar to + <function>sd_journal_open_directory()</function>, but takes a file descriptor referencing a directory in the file + system instead of an absolute file system path.</para> + + <para><function>sd_journal_open_files()</function> is similar to <function>sd_journal_open()</function> but takes a + <constant>NULL</constant>-terminated list of file paths to open. All files will be opened and interleaved + automatically. This call also takes a flags argument, but it must be passed as 0 as no flags are currently + understood for this call. Please note that in the case of a live journal, this function is only useful for + debugging, because individual journal files can be rotated at any moment, and the opening of specific files is + inherently racy.</para> + + <para><function>sd_journal_open_files_fd()</function> is similar to <function>sd_journal_open_files()</function> + but takes an array of open file descriptors that must reference journal files, instead of an array of file system + paths. Pass the array of file descriptors as second argument, and the number of array entries in the third. The + flags parameter must be passed as 0.</para> + + <para><varname>sd_journal</varname> objects cannot be used in the + child after a fork. Functions which take a journal object as an + argument (<function>sd_journal_next()</function> and others) will + return <constant>-ECHILD</constant> after a fork. + </para> + + <para><function>sd_journal_close()</function> will close the + journal context allocated with + <function>sd_journal_open()</function> or + <function>sd_journal_open_directory()</function> and free its + resources.</para> + + <para>When opening the journal only journal files accessible to + the calling user will be opened. If journal files are not + accessible to the caller, this will be silently ignored.</para> + + <para>See + <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> + for an example of how to iterate through the journal after opening + it with <function>sd_journal_open()</function>.</para> + + <para>A journal context object returned by + <function>sd_journal_open()</function> references a specific + journal entry as <emphasis>current</emphasis> entry, similar to a + file seek index in a classic file system file, but without + absolute positions. It may be altered with + <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry> + and + <citerefentry><refentrytitle>sd_journal_seek_head</refentrytitle><manvolnum>3</manvolnum></citerefentry> + and related calls. The current entry position may be exported in + <emphasis>cursor</emphasis> strings, as accessible via + <citerefentry><refentrytitle>sd_journal_get_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>. + Cursor strings may be used to globally identify a specific journal + entry in a stable way and then later to seek to it (or if the + specific entry is not available locally, to its closest entry in + time) + <citerefentry><refentrytitle>sd_journal_seek_cursor</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</para> + + <para>Notification of journal changes is available via + <function>sd_journal_get_fd()</function> and related calls.</para> + </refsect1> + + <refsect1> + <title>Return Value</title> + + <para>The <function>sd_journal_open()</function>, + <function>sd_journal_open_directory()</function>, and + <function>sd_journal_open_files()</function> calls return 0 on + success or a negative errno-style error code. + <function>sd_journal_close()</function> returns nothing.</para> + </refsect1> + + <refsect1> + <title>Notes</title> + + <para>All functions listed here are thread-agnostic and only a single thread may operate + on a given <structname>sd_journal</structname> object.</para> + + <para>The <function>sd_journal_open()</function>, + <function>sd_journal_open_directory()</function> and + <function>sd_journal_close()</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_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-machined</refentrytitle><manvolnum>8</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |