diff options
Diffstat (limited to 'man/sd_journal_query_unique.xml')
| -rw-r--r-- | man/sd_journal_query_unique.xml | 214 |
1 files changed, 214 insertions, 0 deletions
diff --git a/man/sd_journal_query_unique.xml b/man/sd_journal_query_unique.xml new file mode 100644 index 0000000000..f2f8af0eb5 --- /dev/null +++ b/man/sd_journal_query_unique.xml @@ -0,0 +1,214 @@ +<?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 '='.</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 shared library, which can + be compiled and linked to with the + <literal>libsystemd-journal</literal> + <citerefentry><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> |