mirror of
https://github.com/systemd/systemd.git
synced 2024-11-24 10:43:35 +08:00
390 lines
17 KiB
XML
390 lines
17 KiB
XML
<?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 be 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 is 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>, and
|
||
<function>sd_bus_error_set_const()</function>, when successful,
|
||
return the negative errno value corresponding to the
|
||
<parameter>name</parameter> parameter. The 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>
|