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diff --git a/src/libsystemd/sd_journal_query_unique.xml b/src/libsystemd/sd_journal_query_unique.xml new file mode 100644 index 0000000000..d7a41a039c --- /dev/null +++ b/src/libsystemd/sd_journal_query_unique.xml @@ -0,0 +1,215 @@ +<?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_query_unique"> + + <refentryinfo> + <title>sd_journal_query_unique</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_query_unique</refentrytitle> + <manvolnum>3</manvolnum> + </refmeta> + + <refnamediv> + <refname>sd_journal_query_unique</refname> + <refname>sd_journal_enumerate_unique</refname> + <refname>sd_journal_restart_unique</refname> + <refname>SD_JOURNAL_FOREACH_UNIQUE</refname> + <refpurpose>Read unique data fields from the journal</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcsynopsisinfo>#include <systemd/sd-journal.h></funcsynopsisinfo> + + <funcprototype> + <funcdef>int <function>sd_journal_query_unique</function></funcdef> + <paramdef>sd_journal *<parameter>j</parameter></paramdef> + <paramdef>const char *<parameter>field</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef>int <function>sd_journal_enumerate_unique</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_unique</function></funcdef> + <paramdef>sd_journal *<parameter>j</parameter></paramdef> + </funcprototype> + + <funcprototype> + <funcdef><function>SD_JOURNAL_FOREACH_UNIQUE</function></funcdef> + <paramdef>sd_journal *<parameter>j</parameter></paramdef> + <paramdef>const void *<parameter>data</parameter></paramdef> + <paramdef>size_t <parameter>length</parameter></paramdef> + </funcprototype> + + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><function>sd_journal_query_unique()</function> queries the + journal for all unique values the specified field can take. It + takes two arguments: the journal to query and the field name to + look for. Well-known field names are listed on + <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>. + Field names must be specified without a trailing '='. After this + function has been executed successfully the field values may be + queried using <function>sd_journal_enumerate_unique()</function>. + Invoking this call a second time will change the field name being + queried and reset the enumeration index to the first field value + that matches.</para> + + <para><function>sd_journal_enumerate_unique()</function> may be + used to iterate through all data fields which match the previously + selected field name as set with + <function>sd_journal_query_unique()</function>. On each invocation + the next field data matching the field name is returned. The order + of the returned data fields is not defined. It takes three + arguments: the journal context object, plus a pair of pointers to + pointer/size variables where the data object and its size shall be + stored in. The returned data is in a read-only memory map and is + only valid until the next invocation of + <function>sd_journal_enumerate_unique()</function>. Note that the + data returned will be prefixed with the field name and '='. Note + that this call is subject to the data field size threshold as + controlled by + <function>sd_journal_set_data_threshold()</function>.</para> + + <para><function>sd_journal_restart_unique()</function> resets the + data enumeration index to the beginning of the list. The next + invocation of <function>sd_journal_enumerate_unique()</function> + will return the first field data matching the field name + again.</para> + + <para>Note that the + <function>SD_JOURNAL_FOREACH_UNIQUE()</function> macro may be used + as a handy wrapper around + <function>sd_journal_restart_unique()</function> and + <function>sd_journal_enumerate_unique()</function>.</para> + + <para>Note that these functions currently are not influenced by + matches set with <function>sd_journal_add_match()</function> but + this might change in a later version of this software.</para> + + <para>To enumerate all field names currently in use (and thus all suitable field parameters for + <function>sd_journal_query_unique()</function>), use the + <citerefentry><refentrytitle>sd_journal_enumerate_fields</refentrytitle><manvolnum>3</manvolnum></citerefentry> + call.</para> + </refsect1> + + <refsect1> + <title>Return Value</title> + + <para><function>sd_journal_query_unique()</function> returns 0 on + success or a negative errno-style error code. + <function>sd_journal_enumerate_unique()</function> returns a + positive integer if the next field data has been read, 0 when no + more fields are known, or a negative errno-style error code. + <function>sd_journal_restart_unique()</function> returns + nothing.</para> + </refsect1> + + <refsect1> + <title>Notes</title> + + <para>All functions listed here are thread-agnostic and only a single thread may operate + on a given <structname>sd_journal</structname> object.</para> + + <para>The <function>sd_journal_query_unique()</function>, + <function>sd_journal_enumerate_unique()</function> and + <function>sd_journal_restart_unique()</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>Use the <function>SD_JOURNAL_FOREACH_UNIQUE</function> macro + to iterate through all values a field of the journal can take. The + following example lists all unit names referenced in the + journal:</para> + + <programlisting>#include <stdio.h> +#include <string.h> +#include <systemd/sd-journal.h> + +int main(int argc, char *argv[]) { + sd_journal *j; + const void *d; + size_t l; + int r; + + r = sd_journal_open(&j, SD_JOURNAL_LOCAL_ONLY); + if (r < 0) { + fprintf(stderr, "Failed to open journal: %s\n", strerror(-r)); + return 1; + } + r = sd_journal_query_unique(j, "_SYSTEMD_UNIT"); + if (r < 0) { + fprintf(stderr, "Failed to query journal: %s\n", strerror(-r)); + return 1; + } + SD_JOURNAL_FOREACH_UNIQUE(j, d, l) + printf("%.*s\n", (int) l, (const char*) d); + sd_journal_close(j); + return 0; +}</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_enumerate_fields</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>, + <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |