systemd/man/sd_bus_message_dump.xml

<?xml version='1.0'?>
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
<!-- SPDX-License-Identifier: LGPL-2.1-or-later -->

<refentry id="sd_bus_message_dump"
          xmlns:xi="http://www.w3.org/2001/XInclude">

  <refentryinfo>
    <title>sd_bus_message_dump</title>
    <productname>systemd</productname>
  </refentryinfo>

  <refmeta>
    <refentrytitle>sd_bus_message_dump</refentrytitle>
    <manvolnum>3</manvolnum>
  </refmeta>

  <refnamediv>
    <refname>sd_bus_message_dump</refname>
    <refname>sd_bus_message_dump_json</refname>

    <refpurpose>Produce a string representation of a message for debugging purposes</refpurpose>
  </refnamediv>

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

      <funcprototype>
        <funcdef>int sd_bus_message_dump</funcdef>
        <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
        <paramdef>FILE *<parameter>f</parameter></paramdef>
        <paramdef>uint64_t <parameter>flags</parameter></paramdef>
      </funcprototype>

      <funcprototype>
        <funcdef>int sd_bus_message_dump_json</funcdef>
        <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
        <paramdef>uint64_t <parameter>flags</parameter></paramdef>
        <paramdef>sd_json_variant **<parameter>ret</parameter></paramdef>
      </funcprototype>
    </funcsynopsis>
  </refsynopsisdiv>

  <refsect1>
    <title>Description</title>

    <para>The <function>sd_bus_message_dump()</function> function writes a textual representation of the
    message <parameter>m</parameter> to the stream <parameter>f</parameter>. If <parameter>f</parameter> is
    <constant>NULL</constant>, standard output (<constant>stdio</constant>) will be used. This function is
    intended to be used for debugging purposes, and the output is neither stable nor designed to be machine
    readable.</para>

    <para>The <function>sd_bus_message_dump_json()</function> function converts the DBus message
    <parameter>m</parameter> to a JSON variant and stores it in <parameter>ret</parameter>. The caller should
    call <function>sd_json_variant_unref()</function> for the acquired JSON variant after use. Unlike
    <function>sd_bus_message_dump()</function>, the function itself does not print anything. To print the
    DBus message in the JSON format, please pass the returned JSON variant to
    <function>sd_json_variant_dump()</function>.</para>

    <para>The <parameter>flags</parameter> parameter may be used to modify the output, and is a combination
    of zero or more of the following flags:</para>

    <variablelist>
      <varlistentry>
        <term><constant>SD_BUS_MESSAGE_DUMP_WITH_HEADER</constant></term>

        <listitem><para>The header of the message that specifies the message type, flags, and several more
        additional metadata will be printed or included in the resulting JSON object.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><constant>SD_BUS_MESSAGE_DUMP_SUBTREE_ONLY</constant></term>

        <listitem><para>Only the current container will be printed or converted. When the flag is
        <emphasis>not</emphasis> specified, the contents of the whole message will be printed or converted.
        </para></listitem>
      </varlistentry>
    </variablelist>

    <para>Note that these functions move the read pointer of the message. It may be necessary to reset the
    position afterwards, for example with
    <citerefentry><refentrytitle>sd_bus_message_rewind</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
    </para>

  </refsect1>

  <refsect1>
    <title>Examples</title>

    <para>Output for a signal message (with <constant>SD_BUS_MESSAGE_DUMP_WITH_HEADER</constant>):
    <programlisting>
‣ Type=signal  Endian=l  Flags=1  Version=1  Cookie=22
  Path=/value/a  Interface=org.freedesktop.DBus.Properties  Member=PropertiesChanged
  MESSAGE "sa{sv}as" {
          STRING "org.freedesktop.systemd.ValueTest";
          ARRAY "{sv}" {
                  DICT_ENTRY "sv" {
                          STRING "Value";
                          VARIANT "s" {
                                  STRING "object 0x1e, path /value/a";
                          };
                  };
          };
          ARRAY "s" {
                  STRING "Value2";
                  STRING "AnExplicitProperty";
          };
  };
</programlisting>
    </para>
  </refsect1>

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

    <para>On success, this function returns 0 or a positive integer. On failure, it returns a negative
    errno-style error code. No error codes are currently defined.</para>
  </refsect1>

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

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

    <para><simplelist type="inline">
      <member><citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
      <member><citerefentry><refentrytitle>sd-json</refentrytitle><manvolnum>3</manvolnum></citerefentry></member>
    </simplelist></para>
  </refsect1>

</refentry>