man: document sd_journal_get_data() and friends

2 files changed, 217 insertions, 0 deletions

diff --git a/man/sd_journal_get_data.xml b/man/sd_journal_get_data.xml
new file mode 100644
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+<?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_get_data">
+
+        <refentryinfo>
+                <title>sd_journal_get_data</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_get_data</refentrytitle>
+                <manvolnum>3</manvolnum>
+        </refmeta>
+
+        <refnamediv>
+                <refname>sd_journal_get_data</refname>
+                <refname>sd_journal_enumerate_data</refname>
+                <refname>sd_journal_restart_data</refname>
+                <refname>SD_JOURNAL_FOREACH_DATA</refname>
+                <refpurpose>Read data fields from the current journal entry</refpurpose>
+        </refnamediv>
+
+        <refsynopsisdiv>
+                <funcsynopsis>
+                        <funcsynopsisinfo>#include &lt;systemd/sd-journal.h&gt;</funcsynopsisinfo>
+
+                        <funcprototype>
+                                <funcdef>int <function>sd_journal_get_data</function></funcdef>
+                                <paramdef>sd_journal* <parameter>j</parameter></paramdef>
+                                <paramdef>const char* <parameter>field</parameter></paramdef>
+                                <paramdef>const void** <parameter>data</parameter></paramdef>
+                                <paramdef>size_t* <parameter>length</parameter></paramdef>
+                        </funcprototype>
+
+                        <funcprototype>
+                                <funcdef>int <function>sd_journal_enumerate_data</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_restart_data</function></funcdef>
+                                <paramdef>sd_journal* <parameter>j</parameter></paramdef>
+                        </funcprototype>
+
+                        <funcprototype>
+                                <funcdef><function>SD_JOURNAL_FOREACH_DATA</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_get_data()</function> gets
+                the data object associated with a specific field from
+                the current journal entry. It takes four arguments:
+                the journal context object, a string with the field
+                name to request, plus a pair of pointers to
+                pointer/size variables where the data object and its
+                size shall be stored in. The field name should be an
+                entry field name. Well-known field names are listed in
+                <citerefentry><refentrytitle>systemd.journal-fields</refentrytitle><manvolnum>7</manvolnum></citerefentry>. The
+                returned data is in a read-only memory map and is only
+                valid until the next invocation of
+                <function>sd_journal_get_data()</function> or
+                <function>sd_journal_enumerate_data()</function>, or
+                the read pointer is altered. Note that the data
+                returned will be prefixed with the field name and
+                '='.</para>
+
+                <para><function>sd_journal_enumerate_data()</function>
+                may be used to iterate through all fields of the
+                current entry. On each invocation the data for the
+                next field is returned. The order of these fields is
+                not defined. The data returned is in the same format
+                as with <function>sd_journal_get_data()</function> and
+                also follows the same life-time semantics.</para>
+
+                <para><function>sd_journal_restart_data()</function>
+                resets the data enumeration index to the beginning of
+                the entry. The next invocation of
+                <function>sd_journal_enumerate_data()</function> will return the first
+                field of the entry again.</para>
+
+                <para>Note that the
+                <function>SD_JOURNAL_FOREACH_DATA()</function> macro
+                may be used as a wrapper around
+                <function>sd_journal_restart_data()</function> and
+                <function>sd_journal_enumerate_data()</function>.</para>
+
+                <para>Note that these functions will not work before
+                <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                (or related call) has not been called at least
+                once.</para>
+        </refsect1>
+
+        <refsect1>
+                <title>Return Value</title>
+
+                <para><function>sd_journal_get_data()</function>
+                returns 0 on success or a negative errno-style error
+                code. If the current entry does not include the
+                specified field -ENOENT is returned. If
+                <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                has not been called at least once -EADDRNOTAVAIL is
+                returned. <function>sd_journal_enumerate_data()</function>
+                returns a positive integer if the next field has been
+                read, 0 when no more fields are known, or a negative
+                errno-style error
+                code. <function>sd_journal_restart_data()</function>
+                returns nothing.</para>
+        </refsect1>
+
+        <refsect1>
+                <title>Notes</title>
+
+                <para>The <function>sd_journal_get_data()</function>,
+                <function>sd_journal_enumerate_data()</function> and
+                <function>sd_journal_restart_data()</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>See
+                <citerefentry><refentrytitle>sd_journal_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                for a complete example how to use
+                <function>sd_journal_get_data()</function>.</para>
+
+                <para>Use the
+                <function>SD_JOURNAL_FOREACH_DATA</function> macro to
+                iterate through all fields of the current journal
+                entry:</para>
+
+                <programlisting>...
+int print_fields(sd_journal *j) {
+        const void *data;
+        size_t l;
+        SD_JOURNAL_FOREACH_DATA(j, data, length)
+                printf("%.*s\n", (int) length, data);
+}
+...</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_next</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                </para>
+        </refsect1>
+
+</refentry>
diff --git a/man/sd_journal_next.xml b/man/sd_journal_next.xml
index f55ee15744..90fcecb107 100644
--- a/man/sd_journal_next.xml
+++ b/man/sd_journal_next.xml
@@ -47,6 +47,8 @@
                 <refname>sd_journal_previous</refname>
                 <refname>sd_journal_next_skip</refname>
                 <refname>sd_journal_previous_skip</refname>
+                <refname>SD_JOURNAL_FOREACH</refname>
+                <refname>SD_JOURNAL_FOREACH_BACKWARDS</refname>
                 <refpurpose>Advance or set back the read pointer in the journal</refpurpose>
         </refnamediv>
 
@@ -76,6 +78,15 @@
                                 <paramdef>uint64_t <parameter>skip</parameter></paramdef>
                         </funcprototype>
 
+                        <funcprototype>
+                                <funcdef><function>SD_JOURNAL_FOREACH</function></funcdef>
+                                <paramdef>sd_journal* <parameter>j</parameter></paramdef>
+                        </funcprototype>
+
+                        <funcprototype>
+                                <funcdef><function>SD_JOURNAL_FOREACH_BACKWARDS</function></funcdef>
+                                <paramdef>sd_journal* <parameter>j</parameter></paramdef>
+                        </funcprototype>
                 </funcsynopsis>
         </refsynopsisdiv>
 
@@ -105,6 +116,13 @@
                 that the entry then pointing to is later in time than
                 then previous one, or has the same timestamp.</para>
 
+                <para>Note that
+                <citerefentry><refentrytitle>sd_journal_get_data</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+                and related calls will fail unless
+                <function>sd_journal_next()</function> has been
+                invoked at least once in order to position the read
+                pointer on a journal entry.</para>
+
                 <para>Note that the
                 <function>SD_JOURNAL_FOREACH()</function> macro may be used
                 as a wrapper around