diff options
Diffstat (limited to 'man/sd_journal_query_unique.xml')
| -rw-r--r-- | man/sd_journal_query_unique.xml | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/man/sd_journal_query_unique.xml b/man/sd_journal_query_unique.xml new file mode 100644 index 0000000..81ee55b --- /dev/null +++ b/man/sd_journal_query_unique.xml @@ -0,0 +1,175 @@ +<?xml version='1.0'?> <!--*-nxml-*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> + +<refentry id="sd_journal_query_unique" xmlns:xi="http://www.w3.org/2001/XInclude"> + + <refentryinfo> + <title>sd_journal_query_unique</title> + <productname>systemd</productname> + </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_enumerate_available_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_available_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>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>, + but any field can be specified. Field names must be specified without a trailing + <literal>=</literal>. After this function has been executed successfully the field values may be queried + using <function>sd_journal_enumerate_unique()</function> and + <function>sd_journal_enumerate_available_unique()</function>. Invoking one of those calls 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 object, plus a pair of pointers to pointer/size variables where the data object and its size + shall be stored. 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 <literal>=</literal>. Note that this call is subject to the data field + size threshold as controlled by <function>sd_journal_set_data_threshold()</function> and only the initial + part of the field up to the threshold is returned. An error is returned for fields which cannot be + retrieved. See the error list below for details.</para> + + <para><function>sd_journal_enumerate_available_unique()</function> is similar to + <function>sd_journal_enumerate_unique()</function>, but silently skips any fields which may be valid, but + are too large or not supported by current implementation.</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_available_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> and + <function>sd_journal_query_available_unique()</function> return a positive integer if the next field data + has been read, 0 when no more fields remain, or a negative errno-style error code. + <function>sd_journal_restart_unique()</function> doesn't return anything.</para> + + <refsect2> + <title>Errors</title> + + <para>Returned errors may indicate the following problems:</para> + + <variablelist> + <xi:include href="sd_journal_get_data.xml" xpointer="EINVAL"/> + <xi:include href="sd_journal_get_data.xml" xpointer="ECHILD"/> + <xi:include href="sd_journal_get_data.xml" xpointer="EADDRNOTAVAIL"/> + <xi:include href="sd_journal_get_data.xml" xpointer="ENOENT"/> + <xi:include href="sd_journal_get_data.xml" xpointer="ENOBUFS"/> + <xi:include href="sd_journal_get_data.xml" xpointer="E2BIG"/> + <xi:include href="sd_journal_get_data.xml" xpointer="EPROTONOSUPPORT"/> + <xi:include href="sd_journal_get_data.xml" xpointer="EBADMSG"/> + <xi:include href="sd_journal_get_data.xml" xpointer="EIO"/> + </variablelist> + </refsect2> + </refsect1> + + <refsect1> + <title>Notes</title> + + <xi:include href="threads-aware.xml" xpointer="strict"/> + + <xi:include href="libsystemd-pkgconfig.xml" xpointer="pkgconfig-text"/> + </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 (and which can be accessed on the given architecture and are not compressed with + an unsupported mechanism). The following example lists all unit names referenced in the journal:</para> + + <programlisting><xi:include href="journal-iterate-unique.c" parse="text" /></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> |