1<?xml version='1.0'?> <!--*-nxml-*--> 2<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" 3 "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> 4<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> 5 6<refentry id="sd_bus_message_get_type" xmlns:xi="http://www.w3.org/2001/XInclude"> 7 8 <refentryinfo> 9 <title>sd_bus_message_get_type</title> 10 <productname>systemd</productname> 11 </refentryinfo> 12 13 <refmeta> 14 <refentrytitle>sd_bus_message_get_type</refentrytitle> 15 <manvolnum>3</manvolnum> 16 </refmeta> 17 18 <refnamediv> 19 <refname>sd_bus_message_get_type</refname> 20 <refname>sd_bus_message_get_error</refname> 21 <refname>sd_bus_message_get_errno</refname> 22 <refname>sd_bus_message_get_creds</refname> 23 <refname>sd_bus_message_is_signal</refname> 24 <refname>sd_bus_message_is_method_call</refname> 25 <refname>sd_bus_message_is_method_error</refname> 26 27 <refpurpose>Query bus message addressing/credentials metadata</refpurpose> 28 </refnamediv> 29 30 <refsynopsisdiv> 31 <funcsynopsis> 32 <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> 33 34 <funcprototype> 35 <funcdef>int <function>sd_bus_message_get_type</function></funcdef> 36 <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> 37 <paramdef>uint8_t *<parameter>type</parameter></paramdef> 38 </funcprototype> 39 40 <funcprototype> 41 <funcdef>sd_bus_error* <function>sd_bus_message_get_error</function></funcdef> 42 <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> 43 </funcprototype> 44 45 <funcprototype> 46 <funcdef>int <function>sd_bus_message_get_errno</function></funcdef> 47 <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> 48 </funcprototype> 49 50 <funcprototype> 51 <funcdef>sd_bus_creds* <function>sd_bus_message_get_creds</function></funcdef> 52 <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> 53 </funcprototype> 54 55 <funcprototype> 56 <funcdef>int <function>sd_bus_message_is_signal</function></funcdef> 57 <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> 58 <paramdef>const char *<parameter>interface</parameter></paramdef> 59 <paramdef>const char *<parameter>member</parameter></paramdef> 60 </funcprototype> 61 62 <funcprototype> 63 <funcdef>int <function>sd_bus_message_is_method_call</function></funcdef> 64 <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> 65 <paramdef>const char *<parameter>interface</parameter></paramdef> 66 <paramdef>const char *<parameter>member</parameter></paramdef> 67 </funcprototype> 68 69 <funcprototype> 70 <funcdef>int <function>sd_bus_message_is_method_error</function></funcdef> 71 <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> 72 <paramdef>const char *<parameter>name</parameter></paramdef> 73 </funcprototype> 74 </funcsynopsis> 75 76 </refsynopsisdiv> 77 78 <refsect1> 79 <title>Description</title> 80 81 <para><function>sd_bus_message_get_type()</function> returns the type of a message in the output 82 parameter <parameter>type</parameter>, one of <constant>SD_BUS_MESSAGE_METHOD_CALL</constant>, 83 <constant>SD_BUS_MESSAGE_METHOD_RETURN</constant>, <constant>SD_BUS_MESSAGE_METHOD_ERROR</constant>, 84 <constant>SD_BUS_MESSAGE_SIGNAL</constant>. This type is either specified as a parameter when the message 85 is created using 86 <citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 87 or is set automatically when the message is created using 88 <citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 89 <citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 90 <citerefentry><refentrytitle>sd_bus_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry> 91 and similar functions.</para> 92 93 <para><function>sd_bus_message_get_error()</function> returns the error stored in the message 94 <parameter>m</parameter>, if there is any. Otherwise, it returns <constant>NULL</constant>. 95 <function>sd_bus_message_get_errno()</function> returns the error stored in the message 96 <parameter>m</parameter> as a positive errno-style value, if there is any. Otherwise, it returns zero. 97 Errors are mapped to errno values according to the default and any additional registered error mappings. 98 See <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry> and 99 <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>. 100 </para> 101 102 <para><function>sd_bus_message_get_creds()</function> returns the message credentials attached to the 103 message <parameter>m</parameter>. If no credentials are attached to the message, it returns 104 <constant>NULL</constant>. Ownership of the credentials instance is not transferred to the caller and 105 hence should not be freed.</para> 106 107 <para><function>sd_bus_message_is_signal()</function> checks if message <parameter>m</parameter> is a 108 signal message. If <parameter>interface</parameter> is non-null, it also checks if the message has the 109 same interface set. If <parameter>member</parameter> is non-null, it also checks if the message has the 110 same member set. Also see 111 <citerefentry><refentrytitle>sd_bus_message_new_signal</refentrytitle><manvolnum>3</manvolnum></citerefentry>. 112 It returns true when all checks pass.</para> 113 114 <para><function>sd_bus_message_is_method_call()</function> checks if message <parameter>m</parameter> 115 is a method call message. If <parameter>interface</parameter> is non-null, it also checks if the message 116 has the same interface set. If <parameter>member</parameter> is non-null, it also checks if the message 117 has the same member set. Also see 118 <citerefentry><refentrytitle>sd_bus_message_new_method_call</refentrytitle><manvolnum>3</manvolnum></citerefentry>. 119 It returns true when all checks pass.</para> 120 121 <para><function>sd_bus_message_is_method_error()</function> checks if message <parameter>m</parameter> 122 is an error reply message. If <parameter>name</parameter> is non-null, it also checks if the message has 123 the same error identifier set. Also see 124 <citerefentry><refentrytitle>sd_bus_message_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>. 125 It returns true when all checks pass.</para> 126 </refsect1> 127 128 <refsect1> 129 <title>Return Value</title> 130 131 <para>On success, these functions (except <function>sd_bus_message_get_error()</function> and 132 <function>sd_bus_message_get_creds()</function>) return a non-negative integer. On failure, they return a 133 negative errno-style error code. <function>sd_bus_message_get_errno()</function> always returns a 134 non-negative integer, even on failure.</para> 135 136 <refsect2> 137 <title>Errors</title> 138 139 <para>Returned errors may indicate the following problems:</para> 140 141 <variablelist> 142 <varlistentry> 143 <term><constant>-EINVAL</constant></term> 144 145 <listitem><para>The message parameter <parameter>m</parameter> or an output parameter is 146 <constant>NULL</constant>.</para></listitem> 147 </varlistentry> 148 </variablelist> 149 </refsect2> 150 </refsect1> 151 152 <xi:include href="libsystemd-pkgconfig.xml" /> 153 154 <refsect1> 155 <title>See Also</title> 156 157 <para> 158 <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, 159 <citerefentry><refentrytitle>sd-bus</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 160 <citerefentry><refentrytitle>sd_bus_message_new</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 161 <citerefentry><refentrytitle>sd_bus_message_set_destination</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 162 <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>, 163 <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry> 164 </para> 165 </refsect1> 166 167</refentry> 168