mirror of
https://github.com/systemd/systemd.git
synced 2024-11-24 18:53:33 +08:00
b1de39dec8
Logically, this is better, because we're describing a subset of possible return values. Visually this also looks quite good because groff renders refsect2 much less prominently. Also rewrap things, add <constant> in various places, fix some typos.
368 lines
17 KiB
XML
368 lines
17 KiB
XML
<?xml version='1.0'?>
|
|
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd">
|
|
<!-- SPDX-License-Identifier: LGPL-2.1+ -->
|
|
|
|
<refentry id="sd_bus_error" xmlns:xi="http://www.w3.org/2001/XInclude">
|
|
|
|
<refentryinfo>
|
|
<title>sd_bus_error</title>
|
|
<productname>systemd</productname>
|
|
</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_move</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 <parameter>ap</parameter></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_move</function></funcdef>
|
|
<paramdef>sd_bus_error *<parameter>dst</parameter></paramdef>
|
|
<paramdef>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_error_set_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_move()</function> is similar to <function>sd_bus_error_copy()</function>, but will
|
|
move any error information from <parameter>e</parameter> into <parameter>dst</parameter>, resetting the
|
|
former. This function cannot fail, as no new memory is allocated. Note that if <parameter>e</parameter> is not set
|
|
(or <constant>NULL</constant>) <parameter>dst</parameter> is initializated to
|
|
<constant>SD_BUS_ERROR_NULL</constant>. Moreover, if <parameter>dst</parameter> is <constant>NULL</constant> no
|
|
operation is executed on it and and resources held by <parameter>e</parameter> are freed and reset. 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> and <function>sd_bus_error_move()</function> return 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>
|
|
|
|
<refsect2>
|
|
<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>
|
|
</refsect2>
|
|
</refsect1>
|
|
|
|
<xi:include href="libsystemd-pkgconfig.xml" />
|
|
|
|
<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>
|