verify: use manager_load_startable_unit_or_warn() to load units for verification

[thirdparty/systemd.git] / man / udev_new.xml

<?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" [
<!ENTITY % entities SYSTEM "custom-entities.ent" >
%entities;
]>

<!--
  SPDX-License-Identifier: LGPL-2.1+

  This file is part of systemd.

  Copyright 2015 David Herrmann <dh.herrmann@gmail.com>

  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="udev_new"
  xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>udev_new</title>
    <productname>systemd</productname>

    <authorgroup>
      <author>
        <contrib>Developer</contrib>
        <firstname>David</firstname>
        <surname>Herrmann</surname>
        <email>dh.herrmann@gmail.com</email>
      </author>
    </authorgroup>
  </refentryinfo>

  <refmeta>
    <refentrytitle>udev_new</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>udev_new</refname>
    <refname>udev_ref</refname>
    <refname>udev_unref</refname>

    <refpurpose>Create, acquire and release a udev context object</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;libudev.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>struct udev *<function>udev_new</function></funcdef>
        <paramdef><parameter>void</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>struct udev *<function>udev_ref</function></funcdef>
        <paramdef>struct udev *<parameter>udev</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>struct udev *<function>udev_unref</function></funcdef>
        <paramdef>struct udev *<parameter>udev</parameter></paramdef>
      </funcprototype>

    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para><function>udev_new()</function> allocates a new udev context
    object and returns a pointer to it. This object is opaque and must
    not be accessed by the caller via different means than functions
    provided by libudev. Initially, the reference count of the context
    is 1. You can acquire further references, and drop gained references
    via <function>udev_ref()</function> and
    <function>udev_unref()</function>. Once the reference count hits 0,
    the context object is destroyed and freed.</para>
  </refsect1>

  <refsect1>
    <title>Return Value</title>

    <para>On success, <function>udev_new()</function> returns a pointer
    to the allocated udev context. On failure, <constant>NULL</constant>
    is returned. <function>udev_ref()</function> returns the argument
    that it was passed, unmodified. <function>udev_unref()</function>
    always returns <constant>NULL</constant>.</para>
  </refsect1>

  <refsect1>
    <title>See Also</title>

    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
    </para>
  </refsect1>

</refentry>