+++ /dev/null
-<?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">
-
-<!--
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- Copyright 2012 Lennart Poettering
-
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--->
-
-<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>
- </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>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_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
- <citerefentry><refentrytitle>sd_journal_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>
- </para>
- </refsect1>
-
-</refentry>
~ianmdlvl / elogind.git / blobdiff