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Before: libsystemd-daemonpkg-config(1) After: libsystemd-daemon pkg-config(1) This fix is more complicated than it should be due to the consecutive XML elements separated by collapsible whitespace. Merging the lines and separating the XML elements with an en space or a non-breaking space is the only solution that results in one, and only one, space being inserted between them when testing. An em space results in two spaces being inserted.
216 lines
9.8 KiB
XML
216 lines
9.8 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_query_unique">
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<refentryinfo>
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<title>sd_journal_query_unique</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_query_unique</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_query_unique</refname>
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<refname>sd_journal_enumerate_unique</refname>
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<refname>sd_journal_restart_unique</refname>
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<refname>SD_JOURNAL_FOREACH_UNIQUE</refname>
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<refpurpose>Read unique data fields from the journal</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_query_unique</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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</funcprototype>
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<funcprototype>
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<funcdef>int <function>sd_journal_enumerate_unique</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_unique</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_UNIQUE</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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</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_query_unique()</function>
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queries the journal for all unique values the
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specified field can take. It takes two arguments: the
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journal to query and the field name to look
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for. Well-known field names are listed on
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<citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>. Field
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names must be specified without a trailing '='. After
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this function has been executed successfully the field
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values may be queried using
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<function>sd_journal_enumerate_unique()</function>. Invoking
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this call a second time will change the field name
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being queried and reset the enumeration index to the
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first field value that matches.</para>
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<para><function>sd_journal_enumerate_unique()</function>
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may be used to iterate through all data fields which
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match the previously selected field name as set with
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<function>sd_journal_query_unique()</function>. On
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each invocation the next field data matching the field
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name is returned. The order of the returned data
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fields is not defined. It takes three arguments: the
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journal context object, plus a pair of pointers to
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pointer/size variables where the data object and its
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size shall be stored in. The returned data is in a
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read-only memory map and is only valid until the next
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invocation of
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<function>sd_journal_enumerate_unique()</function>. Note
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that the data returned will be prefixed with the field
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name and '='. Note that this call is subject to the
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data field size threshold as controlled by
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<function>sd_journal_set_data_threshold()</function>.</para>
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<para><function>sd_journal_restart_unique()</function>
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resets the data enumeration index to the beginning of
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the list. The next invocation of
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<function>sd_journal_enumerate_unique()</function>
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will return the first field data matching the field
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name again.</para>
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<para>Note that the
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<function>SD_JOURNAL_FOREACH_UNIQUE()</function> macro
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may be used as a handy wrapper around
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<function>sd_journal_restart_unique()</function> and
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<function>sd_journal_enumerate_unique()</function>.</para>
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<para>Note that these functions currently are not
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influenced by matches set with
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<function>sd_journal_add_match()</function> but this
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might change in a later version of this
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software.</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_query_unique()</function>
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returns 0 on success or a negative errno-style error
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code. <function>sd_journal_enumerate_unique()</function>
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returns a positive integer if the next field data has
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been read, 0 when no more fields are known, or a
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negative errno-style error
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code. <function>sd_journal_restart_unique()</function>
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returns nothing.</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_query_unique()</function>,
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<function>sd_journal_enumerate_unique()</function> and
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<function>sd_journal_restart_unique()</function>
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interfaces are available as shared library, which can
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be compiled and linked to with the
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<constant>libsystemd-journal</constant> <citerefentry><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>Use the
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<function>SD_JOURNAL_FOREACH_UNIQUE</function> macro
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to iterate through all values a field of the journal
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can take. The following example lists all unit names
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referenced in the journal:</para>
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<programlisting>#include <stdio.h>
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#include <string.h>
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#include <systemd/sd-journal.h>
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int main(int argc, char *argv[]) {
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sd_journal *j;
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const void *d;
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size_t l;
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int r;
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r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY);
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if (r < 0) {
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fprintf(stderr, "Failed to open journal: %s\n", strerror(-r));
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return 1;
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}
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r = sd_journal_query_unique(j, "_SYSTEMD_UNIT");
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if (r < 0) {
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fprintf(stderr, "Failed to query journal: %s\n", strerror(-r));
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return 1;
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}
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SD_JOURNAL_FOREACH_UNIQUE(j, d, l)
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printf("%.*s\n", (int) l, (const char*) d);
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sd_journal_close(j);
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return 0;
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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_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
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<citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>
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</para>
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</refsect1>
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</refentry>
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