mirror of
https://github.com/systemd/systemd-stable.git
synced 2024-12-24 21:34:08 +03:00
251 lines
12 KiB
XML
251 lines
12 KiB
XML
<?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><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 l;
|
||
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>
|