<?xml version='1.0'?> <!--*- Mode: nxml; nxml-child-indent: 2; indent-tabs-mode: nil -*--> <!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN" "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> <!-- This file is part of systemd. Copyright 2016 Julian Orth 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="sd_bus_message_read_basic"> <refentryinfo> <title>sd_bus_message_read_basic</title> <productname>systemd</productname> <authorgroup> <author> <firstname>Julian</firstname> <surname>Orth</surname> <email>ju.orth@gmail.com</email> </author> </authorgroup> </refentryinfo> <refmeta> <refentrytitle>sd_bus_message_read_basic</refentrytitle> <manvolnum>3</manvolnum> </refmeta> <refnamediv> <refname>sd_bus_message_read_basic</refname> <refpurpose>Read a basic type from a message</refpurpose> </refnamediv> <refsynopsisdiv> <funcsynopsis> <funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo> <funcprototype> <funcdef>int <function>sd_bus_message_read_basic</function></funcdef> <paramdef>sd_bus_message *<parameter>m</parameter></paramdef> <paramdef>char <parameter>type</parameter></paramdef> <paramdef>void *<parameter>p</parameter></paramdef> </funcprototype> </funcsynopsis> </refsynopsisdiv> <refsect1> <title>Description</title> <para> <function>sd_bus_message_read_basic()</function> reads a basic type from a message and advances the read position in the message. The set of basic types and their ascii codes passed in <parameter>type</parameter> are described in the <ulink url="https://dbus.freedesktop.org/doc/dbus-specification.html">D-Bus Specification</ulink>. </para> <para> If <parameter>p</parameter> is not NULL, it should contain a pointer to an appropriate object. For example, if <parameter>type</parameter> is <constant>'y'</constant>, the object passed in <parameter>p</parameter> should have type <code>uint8_t *</code>. If <parameter>type</parameter> is <constant>'s'</constant>, the object passed in <parameter>p</parameter> should have type <code>const char **</code>. Note that, if the basic type is a pointer (e.g., <code>const char *</code> in the case of a string), the pointer is only borrowed and the contents must be copied if they are to be used after the end of the messages lifetime. Similarly, during the lifetime of such a pointer, the message must not be modified. </para> <para> If there is no object of the specified type at the current position in the message, an error is returned. </para> </refsect1> <refsect1> <title>Return Value</title> <para> On success, <function>sd_bus_message_read_basic()</function> returns 0 or a positive integer. On failure, it returns a negative errno-style error code. </para> </refsect1> <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>