man: add libsystemd(3)

Before libsystemd-daemon, libsystemd-journal, libsystemd-id128, etc., were
merged into libsystemd, it was enough to have individual man pages for them.
But they have been delivered as one thing for many years, so it's better to
have a landing page for libsystemd. It mostly directs to individual pages
anyway.

man/libsystemd.xml

@@ -0,0 +1,89 @@
+<?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="libsystemd"
+  xmlns:xi="http://www.w3.org/2001/XInclude">
+
+  <refentryinfo>
+    <title>libsystemd</title>
+    <productname>systemd</productname>
+  </refentryinfo>
+
+  <refmeta>
+    <refentrytitle>libsystemd</refentrytitle>
+    <manvolnum>3</manvolnum>
+  </refmeta>
+
+  <refnamediv>
+    <refname>libsystemd</refname>
+    <refpurpose>Functions for implementing services and interacting with systemd</refpurpose>
+  </refnamediv>
+
+  <refsynopsisdiv>
+    <programlisting>
+#include &lt;systemd/sd-bus.h&gt;
+#include &lt;systemd/sd-bus-vtable.h&gt;
+#include &lt;systemd/sd-bus-protocol.h&gt;
+#include &lt;systemd/sd-daemon.h&gt;
+#include &lt;systemd/sd-device.h&gt;
+#include &lt;systemd/sd-event.h&gt;
+#include &lt;systemd/sd-gpt.h&gt;
+#include &lt;systemd/sd-hwdb.h&gt;
+#include &lt;systemd/sd-id128.h&gt;
+#include &lt;systemd/sd-journal.h&gt;
+#include &lt;systemd/sd-login.h&gt;
+#include &lt;systemd/sd-messages.h&gt;
+#include &lt;systemd/sd-path.h&gt;
+    </programlisting>
+
+    <cmdsynopsis>
+      <command>pkg-config --cflags --libs libsystemd</command>
+    </cmdsynopsis>
+  </refsynopsisdiv>
+
+  <refsect1>
+    <title>Description</title>
+
+    <para>The <filename>libsystemd</filename> library provides functions that allow interacting with various
+    interfaces provided by the
+    <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> service
+    manager, as well as various other functions and constants useful for implementing services in
+    general.</para>
+
+    <para>See
+    <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd-daemon</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd-device</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd-event</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd-hwdb</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd-id128</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    <citerefentry><refentrytitle>sd-journal</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+    and
+    <citerefentry><refentrytitle>sd-login</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    for information about different parts of the library interface.</para>
+  </refsect1>
+
+  <refsect1>
+    <title>Interface stability</title>
+
+    <para>Strict backwards-compatibility is maintained for the API (application programming interface) and
+    ABI (application binary interface). Symbol versioning is used, with symbols only added and never removed.
+    </para>
+  </refsect1>
+
+  <xi:include href="libsystemd-pkgconfig.xml" />
+
+  <refsect1>
+    <title>See Also</title>
+    <para>
+      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>libudev</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <ulink url="https://systemd.io/PORTABILITY_AND_STABILITY/">Interface Portability and Stability Promise</ulink>
+    </para>
+  </refsect1>
+
+</refentry>

man/rules/meson.build

@@ -31,6 +31,7 @@ manpages = [
  ['journald.conf', '5', ['journald.conf.d', 'journald@.conf'], ''],
  ['kernel-command-line', '7', [], ''],
  ['kernel-install', '8', [], 'ENABLE_KERNEL_INSTALL'],
+ ['libsystemd', '3', [], ''],
  ['libudev', '3', [], ''],
  ['loader.conf', '5', [], 'ENABLE_BOOTLOADER'],
  ['locale.conf', '5', [], ''],

man/sd-bus-errors.xml

@@ -274,6 +274,7 @@
 
     <para>
       <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
+      <citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>sd_bus_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>sd_bus_message_set_allow_interactive_authorization</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

man/sd-bus.xml

@@ -34,10 +34,11 @@
   <refsect1>
     <title>Description</title>
 
-    <para><filename>sd-bus.h</filename> provides an implementation of a D-Bus IPC client. See
+    <para><filename>sd-bus.h</filename> is part of
+    <citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
+    provides an implementation of a D-Bus IPC client. See
     <ulink url="https://www.freedesktop.org/software/dbus/" />
-    for more information about D-Bus IPC.
+    for more information about D-Bus IPC.</para>
-    </para>
 
     <para>See
     <literallayout><citerefentry><refentrytitle>sd_bus_add_match</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

man/sd-daemon.xml

@@ -44,10 +44,11 @@
   <refsect1>
     <title>Description</title>
 
-    <para><filename>sd-daemon.h</filename> provides APIs for new-style
+    <para><filename>sd-daemon.h</filename> is part of
-    daemons, as implemented by the
+    <citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
-    <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>
+    provides APIs for new-style daemons, as implemented by the
-    service manager.</para>
+    <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> service
+    manager.</para>
 
     <para>See
     <citerefentry><refentrytitle>sd_listen_fds</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

man/sd-device.xml

@@ -34,8 +34,10 @@
   <refsect1>
     <title>Description</title>
 
-    <para><filename>sd-device.h</filename> provides an API to introspect and enumerate devices on the local
+    <para><filename>sd-device.h</filename> is part of
-    system. It provides a programmatic interface to the database of devices and their properties mananaged by
+    <citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
+    provides an API to introspect and enumerate devices on the local system. It provides a programmatic
+    interface to the database of devices and their properties mananaged by
     <citerefentry><refentrytitle>systemd-udevd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.
     This API is a replacement for
     <citerefentry><refentrytitle>libudev</refentrytitle><manvolnum>3</manvolnum></citerefentry> and

man/sd-event.xml

@@ -34,8 +34,9 @@
   <refsect1>
     <title>Description</title>
 
-    <para><filename>sd-event.h</filename> provides a generic event
+    <para><filename>sd-event.h</filename> is part of
-    loop implementation, based on Linux <citerefentry
+    <citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
+    provides a generic event loop implementation, based on Linux <citerefentry
     project='man-pages'><refentrytitle>epoll</refentrytitle><manvolnum>7</manvolnum></citerefentry>.
     </para>
 

man/sd-hwdb.xml

@@ -34,8 +34,10 @@
   <refsect1>
     <title>Description</title>
 
-    <para><filename>sd-hwdb.h</filename> allows read-only access the systemd database of hardware properties.
+    <para><filename>sd-hwdb.h</filename> is part of
-    See <citerefentry><refentrytitle>hwdb</refentrytitle><manvolnum>7</manvolnum></citerefentry> and
+    <citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry> and allows
+    read-only access the systemd database of hardware properties. See
+    <citerefentry><refentrytitle>hwdb</refentrytitle><manvolnum>7</manvolnum></citerefentry> and
     <citerefentry><refentrytitle>systemd-hwdb</refentrytitle><manvolnum>8</manvolnum></citerefentry> for more
     information about the database.</para>
 

man/sd-id128.xml

@@ -121,11 +121,13 @@
   <refsect1>
     <title>Description</title>
 
-    <para><filename>sd-id128.h</filename> provides APIs to generate, convert, and compare 128-bit ID values.
+    <para><filename>sd-id128.h</filename> is part of
-    The 128-bit ID values processed and generated by these APIs are a generalization of OSF UUIDs as defined
+    <citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
-    by <ulink url="https://tools.ietf.org/html/rfc4122">RFC 4122</ulink> but use a simpler string format.
+    provides APIs to generate, convert, and compare 128-bit ID values. The 128-bit ID values processed and
-    These functions impose no structure on the used IDs, much unlike OSF UUIDs or Microsoft GUIDs, but are
+    generated by these APIs are a generalization of OSF UUIDs as defined by <ulink
-    mostly compatible with those types of IDs.
+    url="https://tools.ietf.org/html/rfc4122">RFC 4122</ulink> but use a simpler string format. These
+    functions impose no structure on the used IDs, much unlike OSF UUIDs or Microsoft GUIDs, but are mostly
+    compatible with those types of IDs.
     </para>
 
     <para>A 128-bit ID is implemented as the following

man/sd-journal.xml

@@ -36,8 +36,9 @@
   <refsect1>
     <title>Description</title>
 
-    <para><filename>sd-journal.h</filename> provides APIs to submit
+    <para><filename>sd-journal.h</filename> is part of
-    and query log entries. The APIs exposed act both as client for the
+    <citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
+    provides APIs to submit and query log entries. The APIs exposed act both as client for the
     <citerefentry><refentrytitle>systemd-journald.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>
     journal service and as parser for the journal files on disk.
     </para>

man/sd-login.xml

@@ -35,9 +35,10 @@
   <refsect1>
     <title>Description</title>
 
-    <para><filename>sd-login.h</filename> provides APIs to introspect
+    <para><filename>sd-login.h</filename> is part of
-    and monitor seat, login session and user status information on the
+    <citerefentry><refentrytitle>libsystemd</refentrytitle><manvolnum>3</manvolnum></citerefentry> and
-    local system. </para>
+    provides APIs to introspect and monitor seat, login session, and user status information on the local
+    system.</para>
 
     <para>Note that these APIs only allow purely passive access and
     monitoring of seats, sessions and users. To actively make changes