+++ /dev/null
-<?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_get_data">
-
- <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>
- <refentrytitle>sd_journal_get_data</refentrytitle>
- <manvolnum>3</manvolnum>
- </refmeta>
-
- <refnamediv>
- <refname>sd_journal_get_data</refname>
- <refname>sd_journal_enumerate_data</refname>
- <refname>sd_journal_restart_data</refname>
- <refname>SD_JOURNAL_FOREACH_DATA</refname>
- <refname>sd_journal_set_data_threshold</refname>
- <refname>sd_journal_get_data_threshold</refname>
- <refpurpose>Read data fields from the current journal entry</refpurpose>
- </refnamediv>
-
- <refsynopsisdiv>
- <funcsynopsis>
- <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_get_data</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- <paramdef>const char *<parameter>field</parameter></paramdef>
- <paramdef>const void **<parameter>data</parameter></paramdef>
- <paramdef>size_t *<parameter>length</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_enumerate_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>
- </funcprototype>
-
- <funcprototype>
- <funcdef><function>SD_JOURNAL_FOREACH_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>int <function>sd_journal_set_data_threshold</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- <paramdef>size_t <parameter>sz</parameter></paramdef>
- </funcprototype>
-
- <funcprototype>
- <funcdef>int <function>sd_journal_get_data_threshold</function></funcdef>
- <paramdef>sd_journal *<parameter>j</parameter></paramdef>
- <paramdef>size_t *<parameter>sz</parameter></paramdef>
- </funcprototype>
- </funcsynopsis>
- </refsynopsisdiv>
-
- <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_enumerate_data()</function> may be used
- to iterate through all fields of the current entry. On each
- invocation the data for the next field is returned. The order of
- these fields is not defined. The data returned is in the same
- format as with <function>sd_journal_get_data()</function> and also
- follows the same life-time semantics.</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 these functions will not work before
- <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- (or related call) has been called at least once, in order to
- position the read pointer at a valid entry.</para>
-
- <para><function>sd_journal_set_data_threshold()</function> may be
- used to change the data field size threshold for data returned by
- <function>sd_journal_get_data()</function>,
- <function>sd_journal_enumerate_data()</function> and
- <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.
- 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
- 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.
- It is recommended to set this threshold as low as possible since
- this relieves the library from having to decompress large
- compressed data objects in full.</para>
-
- <para><function>sd_journal_get_data_threshold()</function> returns
- the currently configured data field size threshold.</para>
- </refsect1>
-
- <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>
- </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>
- </refsect1>
-
- <refsect1>
- <title>Examples</title>
-
- <para>See
- <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- for a complete example how to use
- <function>sd_journal_get_data()</function>.</para>
-
- <para>Use the
- <function>SD_JOURNAL_FOREACH_DATA</function> macro to
- iterate through all fields of the current journal
- entry:</para>
-
- <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>
-
- </refsect1>
-
- <refsect1>
- <title>See Also</title>
-
- <para>
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_query_unique</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- </para>
- </refsect1>
-
-</refentry>
~ianmdlvl / elogind.git / blobdiff