systemd/man/sd_bus_message_new_method_error.xml

<?xml version='1.0'?>
<!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_bus_message_new_method_error"
          xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>sd_bus_message_new_method_error</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_message_new_method_error</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_message_new_method_error</refname>
    <refname>sd_bus_message_new_method_errorf</refname>
    <refname>sd_bus_message_new_method_errno</refname>
    <refname>sd_bus_message_new_method_errnof</refname>

    <refpurpose>Create an error reply for a method call</refpurpose>
  </refnamediv>

  <refsynopsisdiv>
    <funcsynopsis>
      <funcsynopsisinfo>#include &lt;systemd/sd-bus.h&gt;</funcsynopsisinfo>

      <funcprototype>
        <funcdef>int sd_bus_message_new_method_error</funcdef>
        <paramdef>sd_bus_message *<parameter>call</parameter></paramdef>
        <paramdef>sd_bus_message **<parameter>m</parameter></paramdef>
        <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int sd_bus_message_new_method_errorf</funcdef>
        <paramdef>sd_bus_message *<parameter>call</parameter></paramdef>
        <paramdef>sd_bus_message **<parameter>m</parameter></paramdef>
        <paramdef>const char *<parameter>name</parameter></paramdef>
        <paramdef>const char *<parameter>format</parameter></paramdef>
        <paramdef>…</paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int sd_bus_message_new_method_errno</funcdef>
        <paramdef>sd_bus_message *<parameter>call</parameter></paramdef>
        <paramdef>sd_bus_message **<parameter>m</parameter></paramdef>
        <paramdef>int <parameter>error</parameter></paramdef>
        <paramdef>const sd_bus_error *<parameter>p</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int sd_bus_message_new_method_errnof</funcdef>
        <paramdef>sd_bus_message *<parameter>call</parameter></paramdef>
        <paramdef>sd_bus_message **<parameter>m</parameter></paramdef>
        <paramdef>int <parameter>error</parameter></paramdef>
        <paramdef>const char *<parameter>format</parameter></paramdef>
        <paramdef>…</paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>The <function>sd_bus_message_new_method_error()</function> function creates
    a new bus message object that is an error reply to the
    <parameter>call</parameter> message, and returns it in the
    <parameter>m</parameter> output parameter. The error information from error
    <parameter>e</parameter> is appended: the <parameter>name</parameter> field of
    <parameter>e</parameter> is used as the error identifier in the reply header (for
    example an error name such as
    <literal>org.freedesktop.DBus.Error.NotSupported</literal> or the equivalent
    symbolic <constant>SD_BUS_ERROR_NOT_SUPPORTED</constant>), and the
    <parameter>message</parameter> field is set as the human readable error message
    string if present. The error <parameter>e</parameter> must have the
    <parameter>name</parameter> field set, see
    <citerefentry><refentrytitle>sd_bus_error_is_set</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
    </para>

    <para>The <function>sd_bus_message_new_method_errorf()</function> function
    creates an error reply similarly to
    <function>sd_bus_message_new_method_error()</function>, but instead of a ready
    error structure, it takes an error identifier string <parameter>name</parameter>,
    plus a <citerefentry
    project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    format string <parameter>format</parameter> and corresponding arguments. An error
    reply is sent with the error identifier <parameter>name</parameter> and the
    formatted string as the message. <parameter>name</parameter> and
    <parameter>format</parameter> must not be <constant>NULL</constant>.
    </para>

    <para>The <function>sd_bus_message_new_method_errno()</function> function creates
    an error reply similarly to
    <function>sd_bus_message_new_method_error()</function>, but in addition to the
    error structure <parameter>p</parameter>, it takes an
    <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    error value in parameter <parameter>error</parameter>. If the error
    <parameter>p</parameter> is set (see
    <citerefentry><refentrytitle>sd_bus_error_is_set</refentrytitle><manvolnum>3</manvolnum></citerefentry>),
    it is used in the reply. Otherwise, <parameter>error</parameter> is translated to
    an error identifier and used to create a new error structure using
    <citerefentry><refentrytitle>sd_bus_error_set_errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    and that is used in the reply. (If <parameter>error</parameter> is zero, no error
    is actually set, and an error reply with no information is created.)</para>

    <para>The <function>sd_bus_message_new_method_errnof()</function> function
    creates an error reply similarly to
    <function>sd_bus_message_new_method_error()</function>. It takes an
    <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    error value in parameter <parameter>error</parameter>, plus a <citerefentry
    project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    format string <parameter>format</parameter> and corresponding arguments.
    <literal>%m</literal> may be used in the format string to refer to the error
    string corresponding to the specified errno code. The error message is initialized
    using the error identifier generated from <constant>error</constant> and the
    formatted string. (If <parameter>error</parameter> is zero, no error is actually
    set, and an error reply with no information is created.)</para>
  </refsect1>

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

    <para>These functions return 0 if the error reply was successfully created, and a
    negative errno-style error code otherwise.</para>

    <refsect2 id='errors'>
      <title>Errors</title>

      <para>Returned errors may indicate the following problems:</para>

      <variablelist>
        <varlistentry>
          <term><constant>-EINVAL</constant></term>

          <listitem><para>The call message <parameter>call</parameter> or the output
          parameter <parameter>m</parameter> are <constant>NULL</constant>.</para>

          <para>Message <parameter>call</parameter> is not a method call
          message.</para>

          <para>The error <parameter>e</parameter> parameter to
          <function>sd_bus_message_new_method_error()</function> is not set, see
          <citerefentry><refentrytitle>sd_bus_error_is_set</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
          </para>
          </listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-EPERM</constant></term>

          <listitem><para>Message <parameter>call</parameter> has been sealed.
          </para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ENOTCONN</constant></term>

          <listitem><para>The bus to which message <parameter>call</parameter> is
          attached is not connected.</para></listitem>
        </varlistentry>

        <varlistentry>
          <term><constant>-ENOMEM</constant></term>

          <listitem><para>Memory allocation failed.</para></listitem>
        </varlistentry>
      </variablelist>
    </refsect2>
  </refsect1>

  <xi:include href="libsystemd-pkgconfig.xml" />

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

    <para>
      <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>,
      <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>
    </para>
  </refsect1>

</refentry>