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12b42c7667
This did not really work out as we had hoped. Trying to do this upstream introduced several problems that probably makes it better suited as a downstream patch after all. At any rate, it is not releaseable in the current state, so we at least need to revert this before the release. * by adjusting the path to binaries, but not do the same thing to the search path we end up with inconsistent man-pages. Adjusting the search path too would be quite messy, and it is not at all obvious that this is worth the effort, but at any rate it would have to be done before we could ship this. * this means that distributed man-pages does not make sense as they depend on config options, and for better or worse we are still distributing man pages, so that is something that definitely needs sorting out before we could ship with this patch. * we have long held that split-usr is only minimally supported in order to boot, and something we hope will eventually go away. So before we start adding even more magic/effort in order to make this work nicely, we should probably question if it makes sense at all.
236 lines
10 KiB
XML
236 lines
10 KiB
XML
<?xml version='1.0'?> <!--*-nxml-*-->
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
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<!--
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This file is part of systemd.
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Copyright 2012 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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-->
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<refentry id="sd_journal_get_data">
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<refentryinfo>
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<title>sd_journal_get_data</title>
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<productname>systemd</productname>
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<authorgroup>
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<author>
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<contrib>Developer</contrib>
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<firstname>Lennart</firstname>
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<surname>Poettering</surname>
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<email>lennart@poettering.net</email>
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</author>
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</authorgroup>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_journal_get_data</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_data</refname>
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<refname>sd_journal_enumerate_data</refname>
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<refname>sd_journal_restart_data</refname>
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<refname>SD_JOURNAL_FOREACH_DATA</refname>
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<refname>sd_journal_set_data_threshold</refname>
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<refname>sd_journal_get_data_threshold</refname>
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<refpurpose>Read data fields from the current journal 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_data</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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<paramdef>const char *<parameter>field</parameter></paramdef>
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<paramdef>const void **<parameter>data</parameter></paramdef>
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<paramdef>size_t *<parameter>length</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_enumerate_data</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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<paramdef>const void **<parameter>data</parameter></paramdef>
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<paramdef>size_t *<parameter>length</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>void <function>sd_journal_restart_data</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef><function>SD_JOURNAL_FOREACH_DATA</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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<paramdef>const void *<parameter>data</parameter></paramdef>
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<paramdef>size_t <parameter>length</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_set_data_threshold</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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<paramdef>size_t <parameter>sz</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_get_data_threshold</function></funcdef>
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<paramdef>sd_journal *<parameter>j</parameter></paramdef>
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<paramdef>size_t *<parameter>sz</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_data()</function> gets the data
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object associated with a specific field from the current journal
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entry. It takes four arguments: the journal context object, a
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string with the field name to request, plus a pair of pointers to
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pointer/size variables where the data object and its size shall be
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stored in. The field name should be an entry field name.
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Well-known field names are listed in
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
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The returned data is in a read-only memory map and is only valid
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until the next invocation of
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<function>sd_journal_get_data()</function> or
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<function>sd_journal_enumerate_data()</function>, or the read
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pointer is altered. Note that the data returned will be prefixed
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with the field name and '='. Also note that by default data fields
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larger than 64K might get truncated to 64K. This threshold may be
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changed and turned off with
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<function>sd_journal_set_data_threshold()</function> (see
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below).</para>
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<para><function>sd_journal_enumerate_data()</function> may be used
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to iterate through all fields of the current entry. On each
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invocation the data for the next field is returned. The order of
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these fields is not defined. The data returned is in the same
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format as with <function>sd_journal_get_data()</function> and also
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follows the same life-time semantics.</para>
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<para><function>sd_journal_restart_data()</function> resets the
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data enumeration index to the beginning of the entry. The next
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invocation of <function>sd_journal_enumerate_data()</function>
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will return the first field of the entry again.</para>
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<para>Note that the <function>SD_JOURNAL_FOREACH_DATA()</function>
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macro may be used as a handy wrapper around
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<function>sd_journal_restart_data()</function> and
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<function>sd_journal_enumerate_data()</function>.</para>
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<para>Note that these functions will not work before
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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(or related call) has been called at least once, in order to
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position the read pointer at a valid entry.</para>
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<para><function>sd_journal_set_data_threshold()</function> may be
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used to change the data field size threshold for data returned by
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<function>sd_journal_get_data()</function>,
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<function>sd_journal_enumerate_data()</function> and
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<function>sd_journal_enumerate_unique()</function>. This threshold
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is a hint only: it indicates that the client program is interested
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only in the initial parts of the data fields, up to the threshold
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in size -- but the library might still return larger data objects.
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That means applications should not rely exclusively on this
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setting to limit the size of the data fields returned, but need to
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apply a explicit size limit on the returned data as well. This
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threshold defaults to 64K by default. To retrieve the complete
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data fields this threshold should be turned off by setting it to
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0, so that the library always returns the complete data objects.
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It is recommended to set this threshold as low as possible since
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this relieves the library from having to decompress large
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compressed data objects in full.</para>
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<para><function>sd_journal_get_data_threshold()</function> returns
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the currently configured data field size threshold.</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_data()</function> returns 0 on
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success or a negative errno-style error code. If the current entry
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does not include the specified field, -ENOENT is returned. If
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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has not been called at least once, -EADDRNOTAVAIL is returned.
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<function>sd_journal_enumerate_data()</function> returns a
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positive integer if the next field has been read, 0 when no more
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fields are known, or a negative errno-style error code.
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<function>sd_journal_restart_data()</function> returns nothing.
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<function>sd_journal_set_data_threshold()</function> and
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<function>sd_journal_get_threshold()</function> return 0 on
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success or a negative errno-style error code.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<para>The <function>sd_journal_get_data()</function>,
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<function>sd_journal_enumerate_data()</function>,
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<function>sd_journal_restart_data()</function>,
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<function>sd_journal_set_data_threshold()</function> and
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<function>sd_journal_get_data_threshold()</function> interfaces
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are available as a shared library, which can be compiled and
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linked to with the
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<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
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file.</para>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>See
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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for a complete example how to use
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<function>sd_journal_get_data()</function>.</para>
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<para>Use the
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<function>SD_JOURNAL_FOREACH_DATA</function> macro to
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iterate through all fields of the current journal
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entry:</para>
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<programlisting>...
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int print_fields(sd_journal *j) {
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const void *data;
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size_t length;
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SD_JOURNAL_FOREACH_DATA(j, data, length)
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printf("%.*s\n", (int) length, data);
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}
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...</programlisting>
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</refsect1>
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<refsect1>
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<title>See Also</title>
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<para>
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<citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_open</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_get_realtime_usec</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_query_unique</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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