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64a7ef8bc0
Triggered by https://bugzilla.redhat.com/show_bug.cgi?id=1609349 This adds two generic paragaphs we include via xinclude. One is the "strict" version, which contains wording saying that we are thread agnostic and what that means. And the other is the "safe" version, for the cases we provide fully safety. Let's then change most man pages to use either of these generic paragraphs. With one exception: man/sd_journal_get_catalog.xml contains both kinds of function, we hence use manual wording.
137 lines
5.3 KiB
XML
137 lines
5.3 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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SPDX-License-Identifier: LGPL-2.1+
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-->
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<refentry id="sd_journal_enumerate_fields" xmlns:xi="http://www.w3.org/2001/XInclude">
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<refentryinfo>
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<title>sd_journal_enumerate_fields</title>
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<productname>systemd</productname>
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</refentryinfo>
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<refmeta>
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<refentrytitle>sd_journal_enumerate_fields</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_enumerate_fields</refname>
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<refname>sd_journal_restart_fields</refname>
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<refname>SD_JOURNAL_FOREACH_FIELD</refname>
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<refpurpose>Read used field names 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_enumerate_fields</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>void <function>sd_journal_restart_fields</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_FIELD</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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</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_enumerate_fields()</function> may be used to iterate through all field names used in the
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opened journal files. On each invocation the next field name is returned. The order of the returned field names is
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not defined. It takes two arguments: the journal context object, plus a pointer to a constant string pointer where
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the field name is stored in. The returned data is in a read-only memory map and is only valid until the next
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invocation of <function>sd_journal_enumerate_fields()</function>. Note that this call is subject to the data field
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size threshold as controlled by <function>sd_journal_set_data_threshold()</function>.</para>
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<para><function>sd_journal_restart_fields()</function> resets the field name enumeration index to the beginning of
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the list. The next invocation of <function>sd_journal_enumerate_fields()</function> will return the first field
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name again.</para>
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<para>The <function>SD_JOURNAL_FOREACH_FIELD()</function> macro may be used as a handy wrapper around
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<function>sd_journal_restart_fields()</function> and <function>sd_journal_enumerate_fields()</function>.</para>
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<para>These functions currently are not influenced by matches set with <function>sd_journal_add_match()</function>
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but this might change in a later version of this software.</para>
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<para>To retrieve the possible values a specific field can take use
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<citerefentry><refentrytitle>sd_journal_query_unique</refentrytitle><manvolnum>3</manvolnum></citerefentry>.</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_enumerate_fields()</function> returns a
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positive integer if the next field name has been read, 0 when no
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more field names are known, or a negative errno-style error code.
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<function>sd_journal_restart_fields()</function> returns
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nothing.</para>
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</refsect1>
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<refsect1>
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<title>Notes</title>
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<xi:include href="threads-aware.xml" xpointer="strict" />
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<xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/>
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</refsect1>
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<refsect1>
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<title>Examples</title>
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<para>Use the <function>SD_JOURNAL_FOREACH_FIELD</function> macro to iterate through all field names in use in the
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current 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 char *field;
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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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SD_JOURNAL_FOREACH_FIELD(j, field)
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printf("%s\n", field);
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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_query_unique</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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