man/sd_bus_error.xml - systemd-stable - Rivoreo Source Code Repositories

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   This file is part of systemd.

   Copyright 2014 Zbigniew Jędrzejewski-Szmek

   systemd is free software; you can redistribute it and/or modify it
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   the Free Software Foundation; either version 2.1 of the License, or
   (at your option) any later version.

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 <refentry id="sd_bus_error">

   <refentryinfo>
     <title>sd_bus_error</title>
     <productname>systemd</productname>

     <authorgroup>
       <author>
         <contrib>A monkey with a typewriter</contrib>
         <firstname>Zbigniew</firstname>
         <surname>Jędrzejewski-Szmek</surname>
         <email>zbyszek@in.waw.pl</email>
       </author>
     </authorgroup>
   </refentryinfo>

   <refmeta>
     <refentrytitle>sd_bus_error</refentrytitle>
     <manvolnum>3</manvolnum>
   </refmeta>

   <refnamediv>
     <refname>sd_bus_error</refname>
     <refname>SD_BUS_ERROR_MAKE_CONST</refname>
     <refname>SD_BUS_ERROR_NULL</refname>
     <refname>sd_bus_error_free</refname>
     <refname>sd_bus_error_set</refname>
     <refname>sd_bus_error_setf</refname>
     <refname>sd_bus_error_set_const</refname>
     <refname>sd_bus_error_set_errno</refname>
     <refname>sd_bus_error_set_errnof</refname>
     <refname>sd_bus_error_set_errnofv</refname>
     <refname>sd_bus_error_get_errno</refname>
     <refname>sd_bus_error_copy</refname>
     <refname>sd_bus_error_is_set</refname>
     <refname>sd_bus_error_has_name</refname>

     <refpurpose>sd-bus error handling</refpurpose>
   </refnamediv>

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

       <funcsynopsisinfo>typedef struct {
         const char *name;
         const char *message;
         ...
 } sd_bus_error;</funcsynopsisinfo>

       <para>
         <constant>SD_BUS_ERROR_MAKE_CONST(<replaceable>name</replaceable>, <replaceable>message</replaceable>)</constant>
       </para>
       <para>
         <constant>SD_BUS_ERROR_NULL</constant>
       </para>

       <funcprototype>
         <funcdef>void <function>sd_bus_error_free</function></funcdef>
         <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
       </funcprototype>

       <funcprototype>
         <funcdef>int <function>sd_bus_error_set</function></funcdef>
         <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
         <paramdef>const char *<parameter>name</parameter></paramdef>
         <paramdef>const char *<parameter>message</parameter></paramdef>
       </funcprototype>

       <funcprototype>
         <funcdef>int <function>sd_bus_error_setf</function></funcdef>
         <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
         <paramdef>const char *<parameter>name</parameter></paramdef>
         <paramdef>const char *<parameter>format</parameter></paramdef>
         <paramdef>...</paramdef>
       </funcprototype>

       <funcprototype>
         <funcdef>int <function>sd_bus_error_set_const</function></funcdef>
         <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
         <paramdef>const char *<parameter>name</parameter></paramdef>
         <paramdef>const char *<parameter>message</parameter></paramdef>
       </funcprototype>

       <funcprototype>
         <funcdef>int <function>sd_bus_error_set_errno</function></funcdef>
         <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
         <paramdef>int <parameter>error</parameter></paramdef>
       </funcprototype>

       <funcprototype>
         <funcdef>int <function>sd_bus_error_set_errnof</function></funcdef>
         <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
         <paramdef>int <parameter>error</parameter></paramdef>
         <paramdef>const char *<parameter>format</parameter></paramdef>
         <paramdef>...</paramdef>
       </funcprototype>

       <funcprototype>
         <funcdef>int <function>sd_bus_error_set_errnofv</function></funcdef>
         <paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
         <paramdef>int <parameter>error</parameter></paramdef>
         <paramdef>const char *<parameter>format</parameter></paramdef>
         <paramdef>va_list ap</paramdef>
       </funcprototype>

       <funcprototype>
         <funcdef>int <function>sd_bus_error_get_errno</function></funcdef>
         <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
       </funcprototype>

       <funcprototype>
         <funcdef>int <function>sd_bus_error_copy</function></funcdef>
         <paramdef>sd_bus_error *<parameter>dst</parameter></paramdef>
         <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
       </funcprototype>

       <funcprototype>
         <funcdef>int <function>sd_bus_error_is_set</function></funcdef>
         <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
       </funcprototype>

       <funcprototype>
         <funcdef>int <function>sd_bus_error_has_name</function></funcdef>
         <paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
         <paramdef>const char *<parameter>name</parameter></paramdef>
       </funcprototype>
     </funcsynopsis>

   </refsynopsisdiv>

   <refsect1>
     <title>Description</title>

     <para>The <structname>sd_bus_error</structname> structure carries
     information about a D-Bus error condition. The functions described
     below may be used to set and query fields in this structure. The
     <structfield>name</structfield> field contains a short identifier
     of an error. It should follow the rules for error names described
     in the D-Bus specification, subsection <ulink
     url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names">Valid
     Names</ulink>. A number of common, standardized error names are
     described in
     <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
     but additional domain-specific errors may be defined by
     applications. The <structfield>message</structfield> field usually
     contains a human readable string describing the details, but might
     be NULL. An unset <structname>sd_bus_error</structname> structure
     should have both fields initialized to NULL. Set an error
     structure to <constant>SD_BUS_ERROR_NULL</constant> in order to
     reset both fields to NULL. When no longer necessary, resources
     held by the <structname>sd_bus_error</structname>structure should
     be destroyed with <function>sd_bus_error_free()</function>.</para>

     <para><function>sd_bus_error_set()</function> sets an error
     structure to the specified name and message strings. The strings
     will be copied into internal, newly allocated memory. It is
     essential to free the error structure again when it is not
     required anymore (see above). The function will return an
     <varname>errno</varname>-like negative value (see <citerefentry
     project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
     determined from the specified error name.  Various well-known
     D-Bus errors are converted to well-known <varname>errno</varname>
     counterparts, and the other ones to <constant>-EIO</constant>. See
     <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     for a list of well-known error names. Additional error mappings
     may be defined with
     <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
     <parameter>e</parameter> is NULL no error structure is initialized
     but the error is still converted into an
     <varname>errno</varname>-style error. If
     <parameter>name</parameter> is <constant>NULL</constant>, it is
     assumed that no error occurred, and 0 is returned. This means that
     this function may be conveniently used in a
     <function>return</function> statement. If
     <parameter>message</parameter> is NULL no message is set. This
     call can fail if no memory may be allocated for the name and
     message strings, in which case an
     <constant>SD_BUS_ERROR_NO_MEMORY</constant> error might be set
     instead and -ENOMEM returned. Do not use this call on error
     structures that are already initialized. If you intend to reuse an
     error structure free the old data stored in it with
     <function>sd_bus_error_free()</function> first.</para>

     <para><function>sd_bus_error_setf()</function> is similar to
     <function>sd_bus_error_set()</function>, but takes a <citerefentry
     project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     format string and corresponding arguments to generate the
     <structfield>message</structfield> field.</para>

     <para><function>sd_bus_error_set_const()</function> is similar to
     <function>sd_bus_error_set()</function>, but the string parameters
     are not copied internally, and must hence remain constant and
     valid for the lifetime of <parameter>e</parameter>. Use this call
     to avoid memory allocations when setting error structures. Since
     this call does not allocate memory it will not fail with an
     out-of-memory condition, as
     <function>sd_bus_error_set()</function> can, as described
     above. Alternatively, the
     <constant>SD_BUS_ERROR_MAKE_CONST()</constant> macro may be used
     to generate a literal, constant bus error structure
     on-the-fly.</para>

     <para><function>sd_bus_error_set_errno()</function> will set
     <structfield>name</structfield> from an
     <varname>errno</varname>-like value that is converted to a D-Bus
     error. <citerefentry
     project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     will be used to set <structfield>message</structfield>. Well-known
     D-Bus error names will be used for <structfield>name</structfield>
     if applicable, otherwise a name in the
     <literal>System.Error.</literal> namespace will be generated. The
     sign of the specified error number is ignored. The absolute value
     is used implicitly. The call always returns a negative value, for
     convenient usage in <function>return</function> statements. This
     call might fail due to lack of memory, in which case an
     <constant>SD_BUS_ERROR_NO_MEMORY</constant> error is set instead,
     and -ENOMEM returned.</para>

     <para><function>sd_bus_error_set_errnof()</function> is similar to
     <function>sd_bus_error_set_errno()</function>, but in addition to
     <parameter>error</parameter>, takes a <citerefentry
     project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     format string and corresponding arguments.  The
     <structfield>message</structfield> field will be generated from
     <parameter>format</parameter> and the arguments.</para>

     <para><function>sd_bus_error_set_errnofv()</function> is similar to
     <function>sd_bus_error_set_errnof()</function> but takes the
     format string parameters as <citerefentry
     project='man-pages'><refentrytitle>va_arg</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     parameter list.</para>

     <para><function>sd_bus_error_get_errno()</function> converts the
     <structfield>name</structfield> field of an error structure to an
     <varname>errno</varname>-like (positive) value using the same
     rules as <function>sd_bus_error_set()</function>.  If
     <parameter>e</parameter> is <constant>NULL</constant>, 0 will be
     returned.</para>

     <para><function>sd_bus_error_copy()</function> will initialize
     <parameter>dst</parameter> using the values in
     <parameter>e</parameter>. If the strings in
     <parameter>e</parameter> were set using
     <function>sd_bus_set_error_const()</function>, they will be shared.
     Otherwise, they will be copied. Returns a converted
     <varname>errno</varname>-like, negative error code.</para>

     <para><function>sd_bus_error_is_set()</function> will return a
     non-zero value if <parameter>e</parameter> is
     non-<constant>NULL</constant> and an error has been set,
     <constant>false</constant> otherwise.</para>

     <para><function>sd_bus_error_has_name()</function> will return a
     non-zero value if <parameter>e</parameter> is
     non-<constant>NULL</constant> and an error with the same
     <parameter>name</parameter> has been set,
     <constant>false</constant> otherwise.</para>

     <para><function>sd_bus_error_free()</function> will destroy
     resources held by <parameter>e</parameter>. The parameter itself
     will not be deallocated, and must be <citerefentry
     project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>d
     by the caller if necessary. The function may also be called safely
     on unset errors (error structures with both fields set to NULL),
     in which case it performs no operation. This call will reset the
     error structure after freeing the data, so that all fields are set
     to NULL. The structure may be reused afterwards.</para>
   </refsect1>

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

     <para>The functions <function>sd_bus_error_set()</function>,
     <function>sd_bus_error_setf()</function>,
     <function>sd_bus_error_set_const()</function>, when successful,
     return the negative errno value corresponding to the
     <parameter>name</parameter> parameter. Functions
     <function>sd_bus_error_set_errno()</function>,
     <function>sd_bus_error_set_errnof()</function> and
     <function>sd_bus_error_set_errnofv()</function>, when successful,
     return the negative value of the <parameter>error</parameter>
     parameter. If an error occurs, one of the negative error values
     listed below will be returned.</para>

     <para><function>sd_bus_error_get_errno()</function> returns
     <constant>false</constant> when <parameter>e</parameter> is
     <constant>NULL</constant>, and a positive errno value mapped from
     <parameter>e-&gt;name</parameter> otherwise.</para>

     <para><function>sd_bus_error_copy()</function> returns 0 or a
     positive integer on success, and a negative error value converted
     from the error name otherwise.</para>

     <para><function>sd_bus_error_is_set()</function> returns a
     non-zero value when <parameter>e</parameter> and the
     <structfield>name</structfield> field are
     non-<constant>NULL</constant>, zero otherwise.</para>

     <para><function>sd_bus_error_has_name()</function> returns a
     non-zero value when <parameter>e</parameter> is
     non-<constant>NULL</constant> and the
     <structfield>name</structfield> field is equal to
     <parameter>name</parameter>, zero otherwise.</para>
   </refsect1>

   <refsect1>
     <title>Reference ownership</title>
     <para><structname>sd_bus_error</structname> is not reference
     counted. Users should destroy resources held by it by calling
     <function>sd_bus_error_free()</function>. Usually error structures
     are allocated on the stack or passed in as function parameters,
     but they may also be allocated dynamically, in which case it is
     the duty of the caller to <citerefentry
     project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     the memory held by the structure itself after freeing its contents
     with <function>sd_bus_error_free()</function>.</para>
   </refsect1>

   <refsect1>
     <title>Errors</title>

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

     <variablelist>

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

         <listitem><para>Error was already set in
         <structname>sd_bus_error</structname> structure when one the
         error-setting functions was called.</para></listitem>
       </varlistentry>

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

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

   <refsect1>
     <title>Notes</title>

     <para><function>sd_bus_set_error()</function> and other functions
     described here are available as a shared library, which can be
     compiled and linked to with the
     <constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
     file.</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>,
       <citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
       <citerefentry project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry>
     </para>
   </refsect1>

 </refentry>
	<?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 2014 Zbigniew Jędrzejewski-Szmek

	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_error">

	<refentryinfo>
	<title>sd_bus_error</title>
	<productname>systemd</productname>

	<authorgroup>
	<author>
	<contrib>A monkey with a typewriter</contrib>
	<firstname>Zbigniew</firstname>
	<surname>Jędrzejewski-Szmek</surname>
	<email>zbyszek@in.waw.pl</email>
	</author>
	</authorgroup>
	</refentryinfo>

	<refmeta>
	<refentrytitle>sd_bus_error</refentrytitle>
	<manvolnum>3</manvolnum>
	</refmeta>

	<refnamediv>
	<refname>sd_bus_error</refname>
	<refname>SD_BUS_ERROR_MAKE_CONST</refname>
	<refname>SD_BUS_ERROR_NULL</refname>
	<refname>sd_bus_error_free</refname>
	<refname>sd_bus_error_set</refname>
	<refname>sd_bus_error_setf</refname>
	<refname>sd_bus_error_set_const</refname>
	<refname>sd_bus_error_set_errno</refname>
	<refname>sd_bus_error_set_errnof</refname>
	<refname>sd_bus_error_set_errnofv</refname>
	<refname>sd_bus_error_get_errno</refname>
	<refname>sd_bus_error_copy</refname>
	<refname>sd_bus_error_is_set</refname>
	<refname>sd_bus_error_has_name</refname>

	<refpurpose>sd-bus error handling</refpurpose>
	</refnamediv>

	<refsynopsisdiv>
	<funcsynopsis>
	<funcsynopsisinfo>#include <systemd/sd-bus.h></funcsynopsisinfo>

	<funcsynopsisinfo>typedef struct {
	const char *name;
	const char *message;
	...
	} sd_bus_error;</funcsynopsisinfo>

	<para>
	<constant>SD_BUS_ERROR_MAKE_CONST(<replaceable>name</replaceable>, <replaceable>message</replaceable>)</constant>
	</para>
	<para>
	<constant>SD_BUS_ERROR_NULL</constant>
	</para>

	<funcprototype>
	<funcdef>void <function>sd_bus_error_free</function></funcdef>
	<paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
	</funcprototype>

	<funcprototype>
	<funcdef>int <function>sd_bus_error_set</function></funcdef>
	<paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
	<paramdef>const char *<parameter>name</parameter></paramdef>
	<paramdef>const char *<parameter>message</parameter></paramdef>
	</funcprototype>

	<funcprototype>
	<funcdef>int <function>sd_bus_error_setf</function></funcdef>
	<paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
	<paramdef>const char *<parameter>name</parameter></paramdef>
	<paramdef>const char *<parameter>format</parameter></paramdef>
	<paramdef>...</paramdef>
	</funcprototype>

	<funcprototype>
	<funcdef>int <function>sd_bus_error_set_const</function></funcdef>
	<paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
	<paramdef>const char *<parameter>name</parameter></paramdef>
	<paramdef>const char *<parameter>message</parameter></paramdef>
	</funcprototype>

	<funcprototype>
	<funcdef>int <function>sd_bus_error_set_errno</function></funcdef>
	<paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
	<paramdef>int <parameter>error</parameter></paramdef>
	</funcprototype>

	<funcprototype>
	<funcdef>int <function>sd_bus_error_set_errnof</function></funcdef>
	<paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
	<paramdef>int <parameter>error</parameter></paramdef>
	<paramdef>const char *<parameter>format</parameter></paramdef>
	<paramdef>...</paramdef>
	</funcprototype>

	<funcprototype>
	<funcdef>int <function>sd_bus_error_set_errnofv</function></funcdef>
	<paramdef>sd_bus_error *<parameter>e</parameter></paramdef>
	<paramdef>int <parameter>error</parameter></paramdef>
	<paramdef>const char *<parameter>format</parameter></paramdef>
	<paramdef>va_list ap</paramdef>
	</funcprototype>

	<funcprototype>
	<funcdef>int <function>sd_bus_error_get_errno</function></funcdef>
	<paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
	</funcprototype>

	<funcprototype>
	<funcdef>int <function>sd_bus_error_copy</function></funcdef>
	<paramdef>sd_bus_error *<parameter>dst</parameter></paramdef>
	<paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
	</funcprototype>

	<funcprototype>
	<funcdef>int <function>sd_bus_error_is_set</function></funcdef>
	<paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
	</funcprototype>

	<funcprototype>
	<funcdef>int <function>sd_bus_error_has_name</function></funcdef>
	<paramdef>const sd_bus_error *<parameter>e</parameter></paramdef>
	<paramdef>const char *<parameter>name</parameter></paramdef>
	</funcprototype>
	</funcsynopsis>

	</refsynopsisdiv>

	<refsect1>
	<title>Description</title>

	<para>The <structname>sd_bus_error</structname> structure carries
	information about a D-Bus error condition. The functions described
	below may be used to set and query fields in this structure. The
	<structfield>name</structfield> field contains a short identifier
	of an error. It should follow the rules for error names described
	in the D-Bus specification, subsection <ulink
	url="http://dbus.freedesktop.org/doc/dbus-specification.html#message-protocol-names">Valid
	Names</ulink>. A number of common, standardized error names are
	described in
	<citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	but additional domain-specific errors may be defined by
	applications. The <structfield>message</structfield> field usually
	contains a human readable string describing the details, but might
	be NULL. An unset <structname>sd_bus_error</structname> structure
	should have both fields initialized to NULL. Set an error
	structure to <constant>SD_BUS_ERROR_NULL</constant> in order to
	reset both fields to NULL. When no longer necessary, resources
	held by the <structname>sd_bus_error</structname>structure should
	be destroyed with <function>sd_bus_error_free()</function>.</para>

	<para><function>sd_bus_error_set()</function> sets an error
	structure to the specified name and message strings. The strings
	will be copied into internal, newly allocated memory. It is
	essential to free the error structure again when it is not
	required anymore (see above). The function will return an
	<varname>errno</varname>-like negative value (see <citerefentry
	project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>)
	determined from the specified error name. Various well-known
	D-Bus errors are converted to well-known <varname>errno</varname>
	counterparts, and the other ones to <constant>-EIO</constant>. See
	<citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	for a list of well-known error names. Additional error mappings
	may be defined with
	<citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>. If
	<parameter>e</parameter> is NULL no error structure is initialized
	but the error is still converted into an
	<varname>errno</varname>-style error. If
	<parameter>name</parameter> is <constant>NULL</constant>, it is
	assumed that no error occurred, and 0 is returned. This means that
	this function may be conveniently used in a
	<function>return</function> statement. If
	<parameter>message</parameter> is NULL no message is set. This
	call can fail if no memory may be allocated for the name and
	message strings, in which case an
	<constant>SD_BUS_ERROR_NO_MEMORY</constant> error might be set
	instead and -ENOMEM returned. Do not use this call on error
	structures that are already initialized. If you intend to reuse an
	error structure free the old data stored in it with
	<function>sd_bus_error_free()</function> first.</para>

	<para><function>sd_bus_error_setf()</function> is similar to
	<function>sd_bus_error_set()</function>, but takes a <citerefentry
	project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	format string and corresponding arguments to generate the
	<structfield>message</structfield> field.</para>

	<para><function>sd_bus_error_set_const()</function> is similar to
	<function>sd_bus_error_set()</function>, but the string parameters
	are not copied internally, and must hence remain constant and
	valid for the lifetime of <parameter>e</parameter>. Use this call
	to avoid memory allocations when setting error structures. Since
	this call does not allocate memory it will not fail with an
	out-of-memory condition, as
	<function>sd_bus_error_set()</function> can, as described
	above. Alternatively, the
	<constant>SD_BUS_ERROR_MAKE_CONST()</constant> macro may be used
	to generate a literal, constant bus error structure
	on-the-fly.</para>

	<para><function>sd_bus_error_set_errno()</function> will set
	<structfield>name</structfield> from an
	<varname>errno</varname>-like value that is converted to a D-Bus
	error. <citerefentry
	project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	will be used to set <structfield>message</structfield>. Well-known
	D-Bus error names will be used for <structfield>name</structfield>
	if applicable, otherwise a name in the
	<literal>System.Error.</literal> namespace will be generated. The
	sign of the specified error number is ignored. The absolute value
	is used implicitly. The call always returns a negative value, for
	convenient usage in <function>return</function> statements. This
	call might fail due to lack of memory, in which case an
	<constant>SD_BUS_ERROR_NO_MEMORY</constant> error is set instead,
	and -ENOMEM returned.</para>

	<para><function>sd_bus_error_set_errnof()</function> is similar to
	<function>sd_bus_error_set_errno()</function>, but in addition to
	<parameter>error</parameter>, takes a <citerefentry
	project='man-pages'><refentrytitle>printf</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	format string and corresponding arguments. The
	<structfield>message</structfield> field will be generated from
	<parameter>format</parameter> and the arguments.</para>

	<para><function>sd_bus_error_set_errnofv()</function> is similar to
	<function>sd_bus_error_set_errnof()</function> but takes the
	format string parameters as <citerefentry
	project='man-pages'><refentrytitle>va_arg</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	parameter list.</para>

	<para><function>sd_bus_error_get_errno()</function> converts the
	<structfield>name</structfield> field of an error structure to an
	<varname>errno</varname>-like (positive) value using the same
	rules as <function>sd_bus_error_set()</function>. If
	<parameter>e</parameter> is <constant>NULL</constant>, 0 will be
	returned.</para>

	<para><function>sd_bus_error_copy()</function> will initialize
	<parameter>dst</parameter> using the values in
	<parameter>e</parameter>. If the strings in
	<parameter>e</parameter> were set using
	<function>sd_bus_set_error_const()</function>, they will be shared.
	Otherwise, they will be copied. Returns a converted
	<varname>errno</varname>-like, negative error code.</para>

	<para><function>sd_bus_error_is_set()</function> will return a
	non-zero value if <parameter>e</parameter> is
	non-<constant>NULL</constant> and an error has been set,
	<constant>false</constant> otherwise.</para>

	<para><function>sd_bus_error_has_name()</function> will return a
	non-zero value if <parameter>e</parameter> is
	non-<constant>NULL</constant> and an error with the same
	<parameter>name</parameter> has been set,
	<constant>false</constant> otherwise.</para>

	<para><function>sd_bus_error_free()</function> will destroy
	resources held by <parameter>e</parameter>. The parameter itself
	will not be deallocated, and must be <citerefentry
	project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>d
	by the caller if necessary. The function may also be called safely
	on unset errors (error structures with both fields set to NULL),
	in which case it performs no operation. This call will reset the
	error structure after freeing the data, so that all fields are set
	to NULL. The structure may be reused afterwards.</para>
	</refsect1>

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

	<para>The functions <function>sd_bus_error_set()</function>,
	<function>sd_bus_error_setf()</function>,
	<function>sd_bus_error_set_const()</function>, when successful,
	return the negative errno value corresponding to the
	<parameter>name</parameter> parameter. Functions
	<function>sd_bus_error_set_errno()</function>,
	<function>sd_bus_error_set_errnof()</function> and
	<function>sd_bus_error_set_errnofv()</function>, when successful,
	return the negative value of the <parameter>error</parameter>
	parameter. If an error occurs, one of the negative error values
	listed below will be returned.</para>

	<para><function>sd_bus_error_get_errno()</function> returns
	<constant>false</constant> when <parameter>e</parameter> is
	<constant>NULL</constant>, and a positive errno value mapped from
	<parameter>e->name</parameter> otherwise.</para>

	<para><function>sd_bus_error_copy()</function> returns 0 or a
	positive integer on success, and a negative error value converted
	from the error name otherwise.</para>

	<para><function>sd_bus_error_is_set()</function> returns a
	non-zero value when <parameter>e</parameter> and the
	<structfield>name</structfield> field are
	non-<constant>NULL</constant>, zero otherwise.</para>

	<para><function>sd_bus_error_has_name()</function> returns a
	non-zero value when <parameter>e</parameter> is
	non-<constant>NULL</constant> and the
	<structfield>name</structfield> field is equal to
	<parameter>name</parameter>, zero otherwise.</para>
	</refsect1>

	<refsect1>
	<title>Reference ownership</title>
	<para><structname>sd_bus_error</structname> is not reference
	counted. Users should destroy resources held by it by calling
	<function>sd_bus_error_free()</function>. Usually error structures
	are allocated on the stack or passed in as function parameters,
	but they may also be allocated dynamically, in which case it is
	the duty of the caller to <citerefentry
	project='man-pages'><refentrytitle>free</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	the memory held by the structure itself after freeing its contents
	with <function>sd_bus_error_free()</function>.</para>
	</refsect1>

	<refsect1>
	<title>Errors</title>

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

	<variablelist>

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

	<listitem><para>Error was already set in
	<structname>sd_bus_error</structname> structure when one the
	error-setting functions was called.</para></listitem>
	</varlistentry>

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

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

	<refsect1>
	<title>Notes</title>

	<para><function>sd_bus_set_error()</function> and other functions
	described here are available as a shared library, which can be
	compiled and linked to with the
	<constant>libsystemd</constant> <citerefentry project='die-net'><refentrytitle>pkg-config</refentrytitle><manvolnum>1</manvolnum></citerefentry>
	file.</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>,
	<citerefentry><refentrytitle>sd-bus-errors</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	<citerefentry><refentrytitle>sd_bus_error_add_map</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	<citerefentry project='man-pages'><refentrytitle>errno</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
	<citerefentry project='die-net'><refentrytitle>strerror_r</refentrytitle><manvolnum>3</manvolnum></citerefentry>
	</para>
	</refsect1>

	</refentry>