<?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" [
-<!ENTITY % entities SYSTEM "custom-entities.ent" >
-%entities;
-]>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
+<!-- SPDX-License-Identifier: LGPL-2.1+ -->
-<!--
- 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.
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--->
-
-<refentry id="sd_journal_get_data">
+<refentry id="sd_journal_get_data" xmlns:xi="http://www.w3.org/2001/XInclude">
<refentryinfo>
<title>sd_journal_get_data</title>
<productname>systemd</productname>
-
- <authorgroup>
- <author>
- <contrib>Developer</contrib>
- <firstname>Lennart</firstname>
- <surname>Poettering</surname>
- <email>lennart@poettering.net</email>
- </author>
- </authorgroup>
</refentryinfo>
<refmeta>
<refnamediv>
<refname>sd_journal_get_data</refname>
<refname>sd_journal_enumerate_data</refname>
+ <refname>sd_journal_enumerate_available_data</refname>
<refname>sd_journal_restart_data</refname>
<refname>SD_JOURNAL_FOREACH_DATA</refname>
<refname>sd_journal_set_data_threshold</refname>
<paramdef>size_t *<parameter>length</parameter></paramdef>
</funcprototype>
+ <funcprototype>
+ <funcdef>int <function>sd_journal_enumerate_available_data</function></funcdef>
+ <paramdef>sd_journal *<parameter>j</parameter></paramdef>
+ <paramdef>const void **<parameter>data</parameter></paramdef>
+ <paramdef>size_t *<parameter>length</parameter></paramdef>
+ </funcprototype>
+
<funcprototype>
<funcdef>void <function>sd_journal_restart_data</function></funcdef>
<paramdef>sd_journal *<parameter>j</parameter></paramdef>
<refsect1>
<title>Description</title>
- <para><function>sd_journal_get_data()</function> gets the data
- object associated with a specific field from the current journal
- entry. It takes four arguments: the journal context object, a
- string with the field name to request, plus a pair of pointers to
- pointer/size variables where the data object and its size shall be
- stored in. The field name should be an entry field name.
- Well-known field names are listed in
- <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
- The returned data is in a read-only memory map and is only valid
- until the next invocation of
- <function>sd_journal_get_data()</function> or
- <function>sd_journal_enumerate_data()</function>, or the read
- pointer is altered. Note that the data returned will be prefixed
- with the field name and '='. Also note that by default data fields
- larger than 64K might get truncated to 64K. This threshold may be
- changed and turned off with
- <function>sd_journal_set_data_threshold()</function> (see
- below).</para>
+ <para><function>sd_journal_get_data()</function> gets the data object associated with a specific field
+ from the current journal entry. It takes four arguments: the journal context object, a string with the
+ field name to request, plus a pair of pointers to pointer/size variables where the data object and its
+ size shall be stored in. The field name should be an entry field name. Well-known field names are listed in
+ <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
+ but any field can be specified. The returned data is in a read-only memory map and is only valid until
+ the next invocation of <function>sd_journal_get_data()</function>,
+ <function>sd_journal_enumerate_data()</function>,
+ <function>sd_journal_enumerate_available_data()</function>, or when the read pointer is altered. Note
+ that the data returned will be prefixed with the field name and <literal>=</literal>. Also note that, by
+ default, data fields larger than 64K might get truncated to 64K. This threshold may be changed and turned
+ off with <function>sd_journal_set_data_threshold()</function> (see below).</para>
<para><function>sd_journal_enumerate_data()</function> may be used
to iterate through all fields of the current entry. On each
format as with <function>sd_journal_get_data()</function> and also
follows the same life-time semantics.</para>
+ <para><function>sd_journal_enumerate_available_data()</function> is similar to
+ <function>sd_journal_enumerate_data()</function>, but silently skips any fields which may be valid, but
+ are too large or not supported by current implementation.</para>
+
<para><function>sd_journal_restart_data()</function> resets the
data enumeration index to the beginning of the entry. The next
invocation of <function>sd_journal_enumerate_data()</function>
will return the first field of the entry again.</para>
- <para>Note that the <function>SD_JOURNAL_FOREACH_DATA()</function>
- macro may be used as a handy wrapper around
- <function>sd_journal_restart_data()</function> and
- <function>sd_journal_enumerate_data()</function>.</para>
+ <para>Note that the <function>SD_JOURNAL_FOREACH_DATA()</function> macro may be used as a handy wrapper
+ around <function>sd_journal_restart_data()</function> and
+ <function>sd_journal_enumerate_available_data()</function>.</para>
<para>Note that these functions will not work before
<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
<function>sd_journal_enumerate_unique()</function>. This threshold
is a hint only: it indicates that the client program is interested
only in the initial parts of the data fields, up to the threshold
- in size -- but the library might still return larger data objects.
+ in size — but the library might still return larger data objects.
That means applications should not rely exclusively on this
setting to limit the size of the data fields returned, but need to
- apply a explicit size limit on the returned data as well. This
+ apply an explicit size limit on the returned data as well. This
threshold defaults to 64K by default. To retrieve the complete
data fields this threshold should be turned off by setting it to
0, so that the library always returns the complete data objects.
<refsect1>
<title>Return Value</title>
- <para><function>sd_journal_get_data()</function> returns 0 on
- success or a negative errno-style error code. If the current entry
- does not include the specified field, -ENOENT is returned. If
- <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- has not been called at least once, -EADDRNOTAVAIL is returned.
- <function>sd_journal_enumerate_data()</function> returns a
- positive integer if the next field has been read, 0 when no more
- fields are known, or a negative errno-style error code.
- <function>sd_journal_restart_data()</function> returns nothing.
- <function>sd_journal_set_data_threshold()</function> and
- <function>sd_journal_get_threshold()</function> return 0 on
- success or a negative errno-style error code.</para>
+ <para><function>sd_journal_get_data()</function> returns 0 on success or a negative errno-style error
+ code. <function>sd_journal_enumerate_data()</function> and
+ <function>sd_journal_enumerate_available_data()</function> return a positive integer if the next field
+ has been read, 0 when no more fields remain, or a negative errno-style error code.
+ <function>sd_journal_restart_data()</function> doesn't return anything.
+ <function>sd_journal_set_data_threshold()</function> and <function>sd_journal_get_threshold()</function>
+ return 0 on success or a negative errno-style error code.</para>
+
+ <refsect2>
+ <title>Errors</title>
+
+ <para>Returned errors may indicate the following problems:</para>
+
+ <variablelist>
+ <varlistentry id='EINVAL'>
+ <term><constant>-EINVAL</constant></term>
+
+ <listitem><para>One of the required parameters is <constant>NULL</constant> or invalid.
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id='ECHILD'>
+ <term><constant>-ECHILD</constant></term>
+
+ <listitem><para>The journal object was created in a different process.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id='EADDRNOTAVAIL'>
+ <term><constant>-EADDRNOTAVAIL</constant></term>
+
+ <listitem><para>The read pointer is not positioned at a valid entry;
+ <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+ or a related call has not been called at least once.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id='ENOENT'>
+ <term><constant>-ENOENT</constant></term>
+
+ <listitem><para>The current entry does not include the specified field.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id='ENOMEM'>
+ <term><constant>-ENOMEM</constant></term>
+
+ <listitem><para>Memory allocation failed.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id='ENOBUFS'>
+ <term><constant>-ENOBUFS</constant></term>
+
+ <listitem><para>A compressed entry is too large.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id='E2BIG'>
+ <term><constant>-E2BIG</constant></term>
+
+ <listitem><para>The data field is too large for this computer architecture (e.g. above 4 GB on a
+ 32-bit architecture).</para></listitem>
+ </varlistentry>
+
+ <varlistentry id='EPROTONOSUPPORT'>
+ <term><constant>-EPROTONOSUPPORT</constant></term>
+
+ <listitem><para>The journal is compressed with an unsupported method or the journal uses an
+ unsupported feature.</para></listitem>
+ </varlistentry>
+
+ <varlistentry id='EBADMSG'>
+ <term><constant>-EBADMSG</constant></term>
+
+ <listitem><para>The journal is corrupted (possibly just the entry being iterated over).
+ </para></listitem>
+ </varlistentry>
+
+ <varlistentry id='EIO'>
+ <term><constant>-EIO</constant></term>
+
+ <listitem><para>An I/O error was reported by the kernel.</para></listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect2>
</refsect1>
<refsect1>
<title>Notes</title>
- <para>The <function>sd_journal_get_data()</function>,
- <function>sd_journal_enumerate_data()</function>,
- <function>sd_journal_restart_data()</function>,
- <function>sd_journal_set_data_threshold()</function> and
- <function>sd_journal_get_data_threshold()</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>
+ <xi:include href="threads-aware.xml" xpointer="strict"/>
+
+ <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
</refsect1>
<refsect1>
iterate through all fields of the current journal
entry:</para>
- <programlisting>...
+ <programlisting>…
int print_fields(sd_journal *j) {
const void *data;
size_t length;
SD_JOURNAL_FOREACH_DATA(j, data, length)
printf("%.*s\n", (int) length, data);
}
-...</programlisting>
-
+…</programlisting>
</refsect1>
<refsect1>
projects / thirdparty / systemd.git / blobdiff