sd_bus_add_object(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | RETURN VALUE | NOTES | HISTORY | SEE ALSO | NOTES | COLOPHON

SD_BUS_ADD_OBJECT(3)        sd_bus_add_object        SD_BUS_ADD_OBJECT(3)

NAME         top

       sd_bus_add_object, sd_bus_add_fallback, sd_bus_add_object_vtable,
       sd_bus_add_fallback_vtable, sd_bus_add_filter,
       SD_BUS_VTABLE_CAPABILITY, SD_BUS_VTABLE_START, SD_BUS_VTABLE_END,
       SD_BUS_METHOD_WITH_NAMES_OFFSET, SD_BUS_METHOD_WITH_NAMES,
       SD_BUS_METHOD_WITH_OFFSET, SD_BUS_METHOD,
       SD_BUS_SIGNAL_WITH_NAMES, SD_BUS_SIGNAL, SD_BUS_WRITABLE_PROPERTY,
       SD_BUS_PROPERTY, SD_BUS_PARAM - Declare properties and methods for
       a D-Bus path

SYNOPSIS         top

       #include <systemd/sd-bus-vtable.h>

       typedef int (*sd_bus_message_handler_t)(sd_bus_message *m,
                                               void *userdata,
                                               sd_bus_error *ret_error);

       typedef int (*sd_bus_property_get_t)(sd_bus *bus,
                                            const char *path,
                                            const char *interface,
                                            const char *property,
                                            sd_bus_message *reply,
                                            void *userdata,
                                            sd_bus_error *ret_error);

       typedef int (*sd_bus_property_set_t)(sd_bus *bus,
                                            const char *path,
                                            const char *interface,
                                            const char *property,
                                            sd_bus_message *value,
                                            void *userdata,
                                            sd_bus_error *ret_error);

       typedef int (*sd_bus_object_find_t)(const char *path,
                                           const char *interface,
                                           void *userdata,
                                           void **ret_found,
                                           sd_bus_error *ret_error);

       int sd_bus_add_object(sd_bus *bus, sd_bus_slot **slot,
                             const char *path,
                             sd_bus_message_handler_t callback,
                             void *userdata);

       int sd_bus_add_fallback(sd_bus *bus, sd_bus_slot **slot,
                               const char *path,
                               sd_bus_message_handler_t callback,
                               void *userdata);

       int sd_bus_add_object_vtable(sd_bus *bus, sd_bus_slot **slot,
                                    const char *path,
                                    const char *interface,
                                    const sd_bus_vtable *vtable,
                                    void *userdata);

       int sd_bus_add_fallback_vtable(sd_bus *bus, sd_bus_slot **slot,
                                      const char *prefix,
                                      const char *interface,
                                      const sd_bus_vtable *vtable,
                                      sd_bus_object_find_t find,
                                      void *userdata);

       int sd_bus_add_filter(sd_bus *bus, sd_bus_slot **slot,
                             sd_bus_message_handler_t callback,
                             void *userdata);

       SD_BUS_VTABLE_CAPABILITY(capability)

       SD_BUS_VTABLE_START(flags)

       SD_BUS_VTABLE_END

       SD_BUS_METHOD_WITH_ARGS_OFFSET(member, args, result, handler,
       offset, flags)

       SD_BUS_METHOD_WITH_ARGS(member, args, result, handler, flags)

       SD_BUS_METHOD_WITH_NAMES_OFFSET(member, signature, in_names,
       result, out_names, handler, offset, flags)

       SD_BUS_METHOD_WITH_NAMES(member, signature, in_names, result,
       out_names, handler, flags)

       SD_BUS_METHOD_WITH_OFFSET(member, signature, result, handler,
       offset, flags)

       SD_BUS_METHOD(member, signature, result, handler, flags)

       SD_BUS_SIGNAL_WITH_ARGS(member, args, flags)

       SD_BUS_SIGNAL_WITH_NAMES(member, signature, names, flags)

       SD_BUS_SIGNAL(member, signature, flags)

       SD_BUS_WRITABLE_PROPERTY(member, signature, get, set, offset,
       flags)

       SD_BUS_PROPERTY(member, signature, get, offset, flags)

       SD_BUS_PARAM(name)

       SD_BUS_ARGS(...)

       SD_BUS_RESULT(...)

       SD_BUS_NO_ARGS

       SD_BUS_NO_RESULT

DESCRIPTION         top

       sd_bus_add_object_vtable() is used to declare attributes for the
       object path path connected to the bus connection bus under the
       interface interface. The table vtable may contain property
       declarations using SD_BUS_PROPERTY() or
       SD_BUS_WRITABLE_PROPERTY(), method declarations using
       SD_BUS_METHOD(), SD_BUS_METHOD_WITH_NAMES(),
       SD_BUS_METHOD_WITH_OFFSET(), or SD_BUS_METHOD_WITH_NAMES_OFFSET(),
       and signal declarations using SD_BUS_SIGNAL_WITH_NAMES() or
       SD_BUS_SIGNAL(), see below. The userdata parameter contains a
       pointer that will be passed to various callback functions. It may
       be specified as NULL if no value is necessary. An interface can
       have any number of vtables attached to it.

       sd_bus_add_fallback_vtable() is similar to
       sd_bus_add_object_vtable(), but is used to register "fallback"
       attributes. When looking for an attribute declaration, bus object
       paths registered with sd_bus_add_object_vtable() are checked
       first. If no match is found, the fallback vtables are checked for
       each prefix of the bus object path, i.e. with the last
       slash-separated components successively removed. This allows the
       vtable to be used for an arbitrary number of dynamically created
       objects.

       Parameter find is a function which is used to locate the target
       object based on the bus object path path. It must return 1 and set
       the ret_found output parameter if the object is found, return 0 if
       the object was not found, and return a negative errno-style error
       code or initialize the error structure ret_error on error. The
       pointer passed in ret_found will be used as the userdata parameter
       for the callback functions (offset by the offset offsets as
       specified in the vtable entries).

       sd_bus_add_object() attaches a callback directly to the object
       path path. An object path can have any number of callbacks
       attached to it. Each callback is prepended to the list of
       callbacks which are always called in order.  sd_bus_add_fallback()
       is similar to sd_bus_add_object() but applies to fallback paths
       instead.

       sd_bus_add_filter() installs a callback that is invoked for each
       incoming D-Bus message. Filters can be used to handle logic common
       to all messages received by a service (e.g. authentication or
       authorization).

       When a request is received, any associated callbacks are called
       sequentially until a callback returns a non-zero integer. Return
       zero from a callback to give other callbacks the chance to process
       the request. Callbacks are called in the following order: first,
       global callbacks installed with sd_bus_add_filter() are called.
       Second, callbacks attached directly to the request object path are
       called, followed by any D-Bus method callbacks attached to the
       request object path, interface and member. Finally, the property
       callbacks attached to the request object path, interface and
       member are called. If the final callback returns zero, an error
       reply is sent back to the caller indicating no matching object for
       the request was found.

       Note that you can return a positive integer from a method callback
       without immediately sending a reply. This informs sd-bus this
       callback will take responsibility for replying to the request
       without forcing the callback to produce a reply immediately. This
       allows a callback to perform any number of asynchronous operations
       required to construct a reply. However, if producing a reply takes
       too long, the method call will time out at the caller. This is
       only available to methods and not properties.

       If a callback was invoked to handle a request that expects a reply
       and the callback returns a negative value, the value is
       interpreted as a negative errno-style error code and sent back to
       the caller as a D-Bus error as if sd_bus_reply_method_errno(3) was
       called. Additionally, all callbacks take a sd_bus_error output
       parameter that can be used to provide more detailed error
       information. If ret_error is set when the callback finishes, the
       corresponding D-Bus error is sent back to the caller as if
       sd_bus_reply_method_error(3) was called. Any error stored in
       ret_error takes priority over any negative values returned by the
       same callback when determining which error to send back to the
       caller. Use sd_bus_error_set(3) or one of its variants to set
       ret_error and return a negative integer from a callback with a
       single function call. To send an error reply after a callback has
       already finished, use sd_bus_reply_method_errno(3) or one of its
       variants.

       For all functions, a match slot is created internally. If the
       output parameter slot is NULL, a "floating" slot object is
       created, see sd_bus_slot_set_floating(3). Otherwise, a pointer to
       the slot object is returned. In that case, the reference to the
       slot object should be dropped when the vtable is not needed
       anymore, see sd_bus_slot_unref(3).

   The sd_bus_vtable array
       The array consists of the structures of type sd_bus_vtable, but it
       should never be filled in manually, but through one of the
       following macros:

       SD_BUS_VTABLE_START(flags), SD_BUS_VTABLE_END
           Those must always be the first and last element. The flags
           parameter can be used to set attributes that apply to the
           whole array; see the "Flags" section below.

       SD_BUS_METHOD_WITH_ARGS_OFFSET(), SD_BUS_METHOD_WITH_ARGS()
           Declare a D-Bus method with the name member, arguments args
           and result result.  args expects a sequence of argument
           type/name pairs wrapped in the SD_BUS_ARGS() macro. The
           elements at even indices in this list describe the types of
           the method's arguments. The method's parameter signature is
           the concatenation of all the string literals at even indices
           in args. If a method has no parameters, pass SD_BUS_NO_ARGS to
           args. The elements at uneven indices describe the names of the
           method's arguments.  result expects a sequence of type/name
           pairs wrapped in the SD_BUS_RESULT() macro in the same format
           as SD_BUS_ARGS(). The method's result signature is the
           concatenation of all the string literals at even indices in
           result. If a method has no result, pass SD_BUS_NO_RESULT to
           result. Note that argument types are expected to be quoted
           string literals and argument names are expected to be unquoted
           string literals. See below for a complete example.

           The handler function handler must be of type
           sd_bus_message_handler_t. It will be called to handle the
           incoming messages that call this method. It receives a pointer
           that is the userdata parameter passed to the registration
           function offset by offset bytes. This may be used to pass
           pointers to different fields in the same data structure to
           different methods in the same vtable. To send a reply from
           handler, call sd_bus_reply_method_return(3) with the message
           the callback was invoked with. Parameter flags is a
           combination of flags, see below.

           SD_BUS_METHOD_WITH_ARGS() is a shorthand for calling
           SD_BUS_METHOD_WITH_ARGS_OFFSET() with an offset of zero.

       SD_BUS_METHOD_WITH_NAMES_OFFSET(), SD_BUS_METHOD_WITH_NAMES(),
       SD_BUS_METHOD_WITH_OFFSET(), SD_BUS_METHOD()
           Declare a D-Bus method with the name member, parameter
           signature signature, result signature result. Parameters
           in_names and out_names specify the argument names of the input
           and output arguments in the function signature.  in_names and
           out_names should be created using the SD_BUS_PARAM() macro,
           see below. In all other regards, this macro behaves exactly
           the same as SD_BUS_METHOD_WITH_ARGS_OFFSET().

           SD_BUS_METHOD_WITH_NAMES(), SD_BUS_METHOD_WITH_OFFSET(), and
           SD_BUS_METHOD() are variants which specify zero offset
           (userdata parameter is passed with no change), leave the names
           unset (i.e. no parameter names), or both.

           Prefer using SD_BUS_METHOD_WITH_ARGS_OFFSET() and
           SD_BUS_METHOD_WITH_ARGS() over these macros as they allow
           specifying argument types and names next to each other which
           is less error-prone than first specifying all argument types
           followed by specifying all argument names.

       SD_BUS_SIGNAL_WITH_ARGS()
           Declare a D-Bus signal with the name member and arguments
           args.  args expects a sequence of argument type/name pairs
           wrapped in the SD_BUS_ARGS() macro. The elements at even
           indices in this list describe the types of the signal's
           arguments. The signal's parameter signature is the
           concatenation of all the string literals at even indices in
           args. If a signal has no parameters, pass SD_BUS_NO_ARGS to
           args. The elements at uneven indices describe the names of the
           signal's arguments. Parameter flags is a combination of flags.
           See below for a complete example.

       SD_BUS_SIGNAL_WITH_NAMES(), SD_BUS_SIGNAL()
           Declare a D-Bus signal with the name member, parameter
           signature signature, and argument names names.  names should
           be created using the SD_BUS_PARAM() macro, see below.
           Parameter flags is a combination of flags, see below.

           SD_BUS_SIGNAL() is equivalent to SD_BUS_SIGNAL_WITH_NAMES()
           with the names parameter unset (i.e. no parameter names).

           Prefer using SD_BUS_SIGNAL_WITH_ARGS() over these macros as it
           allows specifying argument types and names next to each other
           which is less error-prone than first specifying all argument
           types followed by specifying all argument names.

       SD_BUS_WRITABLE_PROPERTY(), SD_BUS_PROPERTY()
           Declare a D-Bus property with the name member and value
           signature signature. Parameters get and set are the getter and
           setter methods. They are called with a pointer that is the
           userdata parameter passed to the registration function offset
           by offset bytes. This may be used pass pointers to different
           fields in the same data structure to different setters and
           getters in the same vtable. Parameter flags is a combination
           of flags, see below.

           The setter and getter methods may be omitted (specified as
           NULL), if the property is one of the basic types or "as" in
           case of read-only properties. In those cases, the userdata and
           offset parameters must together point to a valid variable of
           the corresponding type. A default setter and getter will be
           provided, which simply copy the argument between this variable
           and the message.

           SD_BUS_PROPERTY() is used to define a read-only property.

       SD_BUS_PARAM()
           Parameter names should be wrapped in this macro, see the
           example below.

   Flags
       The flags parameter is used to specify a combination of D-Bus
       annotations[1].

       SD_BUS_VTABLE_DEPRECATED
           Mark this vtable entry as deprecated using the
           org.freedesktop.DBus.Deprecated annotation in introspection
           data. If specified for SD_BUS_VTABLE_START(), the annotation
           is applied to the enclosing interface.

       SD_BUS_VTABLE_HIDDEN
           Make this vtable entry hidden. It will not be shown in
           introspection data. If specified for SD_BUS_VTABLE_START(),
           all entries in the array are hidden.

       SD_BUS_VTABLE_METHOD_NO_REPLY
           Mark this vtable entry as a method that will not return a
           reply using the org.freedesktop.DBus.Method.NoReply annotation
           in introspection data.

       SD_BUS_VTABLE_PROPERTY_CONST, SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE,
       SD_BUS_VTABLE_PROPERTY_EMITS_INVALIDATION
           Those three flags correspond to different values of the
           org.freedesktop.DBus.Property.EmitsChangedSignal annotation,
           which specifies whether the
           org.freedesktop.DBus.Properties.PropertiesChanged signal is
           emitted whenever the property changes.
           SD_BUS_VTABLE_PROPERTY_CONST corresponds to const and means
           that the property never changes during the lifetime of the
           object it belongs to, so no signal needs to be emitted.
           SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE corresponds to true and
           means that the signal is emitted.
           SD_BUS_VTABLE_PROPERTY_EMITS_INVALIDATION corresponds to
           invalidates and means that the signal is emitted, but the
           value is not included in the signal.

       SD_BUS_VTABLE_PROPERTY_EXPLICIT
           Mark this vtable property entry as requiring explicit request
           to for the value to be shown (generally because the value is
           large or slow to calculate). This entry cannot be combined
           with SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE, and will not be
           shown in property listings by default (e.g.  busctl
           introspect). This corresponds to the
           org.freedesktop.systemd1.Explicit annotation in introspection
           data.

       SD_BUS_VTABLE_SENSITIVE
           Mark this vtable method entry as processing sensitive data.
           When set, incoming method call messages and their outgoing
           reply messages are marked as sensitive using
           sd_bus_message_sensitive(3), so that they are erased from
           memory when freed.

       SD_BUS_VTABLE_ABSOLUTE_OFFSET
           Mark this vtable method or property entry so that the user
           data pointer passed to its associated handler functions is
           determined slightly differently: instead of adding the offset
           parameter of the entry to the user data pointer specified
           during vtable registration, the offset is passed directly,
           converted to a pointer, without taking the user data pointer
           specified during vtable registration into account.

       SD_BUS_VTABLE_CAPABILITY(capability)
           Access to this vtable entry will be allowed if the calling
           process has the capability capability, as described in
           sd_bus_query_sender_privilege(3). If used for
           SD_BUS_VTABLE_START(), provides a default for all entries in
           the array. If not specified, either for an individual entry or
           the whole array, CAP_SYS_ADMIN is checked by default. See
           capabilities(7) for information about capabilities.

           Note that vtable entries may be marked as unprivileged and the
           whole bus may be marked as trusted, see the discussion of
           SD_BUS_VTABLE_UNPRIVILEGED below.

       SD_BUS_VTABLE_UNPRIVILEGED
           Mark this vtable entry as unprivileged. Access to privileged
           entries is limited to users with appropriate capabilities as
           described above. In practice many vtable entries are marked as
           unprivileged, and either are open to everyone, or the decision
           whether to allow access is taken later, e.g. by delegating to
           polkit[2].

           The whole bus may be marked as trusted, in which case
           annotations at the entry level are ignored, see
           sd_bus_set_trusted(3).

           When not specified, the org.freedesktop.systemd1.Privileged
           annotation with value "true" will be shown in introspection
           data.

           SD_BUS_VTABLE_UNPRIVILEGED may not be applied to read-only
           properties, but read access (to both read-only and writable
           properties) is always unrestricted.

           Note that this page describes checks implemented in the D-Bus
           client. The D-Bus server has an additional policy that may
           permit or deny connections, see "CONFIGURATION FILE" in
           dbus-daemon(1).

EXAMPLES         top

       Example 1. Create a simple listener on the bus

           /* SPDX-License-Identifier: MIT-0 */

           #define _GNU_SOURCE 1
           #include <errno.h>
           #include <stdbool.h>
           #include <stddef.h>
           #include <stdlib.h>
           #include <stdio.h>
           #include <systemd/sd-bus.h>

           #define _cleanup_(f) __attribute__((cleanup(f)))

           typedef struct object {
             char *name;
             uint32_t number;
           } object;

           static int method(sd_bus_message *m, void *userdata, sd_bus_error *error) {
             int r;

             printf("Got called with userdata=%p\n", userdata);

             if (sd_bus_message_is_method_call(m,
                                               "org.freedesktop.systemd.VtableExample",
                                               "Method4"))
               return 1;

             const char *string;
             r = sd_bus_message_read(m, "s", &string);
             if (r < 0) {
               fprintf(stderr, "sd_bus_message_read() failed: %s\n", strerror(-r));
               return 0;
             }

             r = sd_bus_reply_method_return(m, "s", string);
             if (r < 0) {
               fprintf(stderr, "sd_bus_reply_method_return() failed: %s\n", strerror(-r));
               return 0;
             }

             return 1;
           }

           static const sd_bus_vtable vtable[] = {
                   SD_BUS_VTABLE_START(0),
                   SD_BUS_METHOD(
                       "Method1", "s", "s", method, 0),
                   SD_BUS_METHOD_WITH_NAMES_OFFSET(
                       "Method2",
                       "so", SD_BUS_PARAM(string) SD_BUS_PARAM(path),
                       "s", SD_BUS_PARAM(returnstring),
                       method, offsetof(object, number),
                       SD_BUS_VTABLE_DEPRECATED),
                   SD_BUS_METHOD_WITH_ARGS_OFFSET(
                       "Method3",
                       SD_BUS_ARGS("s", string, "o", path),
                       SD_BUS_RESULT("s", returnstring),
                       method, offsetof(object, number),
                       SD_BUS_VTABLE_UNPRIVILEGED),
                   SD_BUS_METHOD_WITH_ARGS(
                       "Method4",
                       SD_BUS_NO_ARGS,
                       SD_BUS_NO_RESULT,
                       method,
                       SD_BUS_VTABLE_UNPRIVILEGED),
                   SD_BUS_SIGNAL(
                       "Signal1",
                       "so",
                       0),
                   SD_BUS_SIGNAL_WITH_NAMES(
                       "Signal2",
                       "so", SD_BUS_PARAM(string) SD_BUS_PARAM(path),
                       0),
                   SD_BUS_SIGNAL_WITH_ARGS(
                       "Signal3",
                       SD_BUS_ARGS("s", string, "o", path),
                       0),
                   SD_BUS_WRITABLE_PROPERTY(
                       "AutomaticStringProperty", "s", NULL, NULL,
                       offsetof(object, name),
                       SD_BUS_VTABLE_PROPERTY_EMITS_CHANGE),
                   SD_BUS_WRITABLE_PROPERTY(
                       "AutomaticIntegerProperty", "u", NULL, NULL,
                       offsetof(object, number),
                       SD_BUS_VTABLE_PROPERTY_EMITS_INVALIDATION),
                   SD_BUS_VTABLE_END
           };

           int main(int argc, char **argv) {
             _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
             int r;

             sd_bus_default(&bus);

             object object = { .number = 666 };
             object.name = strdup("name");
             if (!object.name) {
               fprintf(stderr, "OOM\n");
               return EXIT_FAILURE;
             }

             r = sd_bus_add_object_vtable(bus, NULL,
                                          "/org/freedesktop/systemd/VtableExample",
                                          "org.freedesktop.systemd.VtableExample",
                                          vtable,
                                          &object);
             if (r < 0) {
               fprintf(stderr, "sd_bus_add_object_vtable() failed: %s\n", strerror(-r));
               return EXIT_FAILURE;
             }

             r = sd_bus_request_name(bus,
                                     "org.freedesktop.systemd.VtableExample",
                                     0);
             if (r < 0) {
               fprintf(stderr, "sd_bus_request_name() failed: %s\n", strerror(-r));
               return EXIT_FAILURE;
             }

             for (;;) {
               r = sd_bus_wait(bus, UINT64_MAX);
               if (r < 0) {
                 fprintf(stderr, "sd_bus_wait() failed: %s\n", strerror(-r));
                 return EXIT_FAILURE;
               }

               r = sd_bus_process(bus, NULL);
               if (r < 0) {
                 fprintf(stderr, "sd_bus_process() failed: %s\n", strerror(-r));
                 return EXIT_FAILURE;
               }
             }

             r = sd_bus_release_name(bus, "org.freedesktop.systemd.VtableExample");
             if (r < 0) {
               fprintf(stderr, "sd_bus_release_name() failed: %s\n", strerror(-r));
               return EXIT_FAILURE;
             }

             free(object.name);

             return 0;
           }

       This creates a simple client on the bus (the user bus, when run as
       normal user). We may use the D-Bus
       org.freedesktop.DBus.Introspectable.Introspect call to acquire the
       XML description of the interface:

           <!DOCTYPE node PUBLIC "-//freedesktop//DTD D-BUS Object Introspection 1.0//EN"
           "https://www.freedesktop.org/standards/dbus/1.0/introspect.dtd">
           <!-- SPDX-License-Identifier: LGPL-2.1-or-later -->
           <node>
            <interface name="org.freedesktop.DBus.Peer">
             <method name="Ping"/>
             <method name="GetMachineId">
              <arg type="s" name="machine_uuid" direction="out"/>
             </method>
            </interface>
            <interface name="org.freedesktop.DBus.Introspectable">
             <method name="Introspect">
              <arg name="xml_data" type="s" direction="out"/>
             </method>
            </interface>
            <interface name="org.freedesktop.DBus.Properties">
             <method name="Get">
              <arg name="interface_name" direction="in" type="s"/>
              <arg name="property_name" direction="in" type="s"/>
              <arg name="value" direction="out" type="v"/>
             </method>
             <method name="GetAll">
              <arg name="interface_name" direction="in" type="s"/>
              <arg name="props" direction="out" type="a{sv}"/>
             </method>
             <method name="Set">
              <arg name="interface_name" direction="in" type="s"/>
              <arg name="property_name" direction="in" type="s"/>
              <arg name="value" direction="in" type="v"/>
             </method>
             <signal name="PropertiesChanged">
              <arg type="s" name="interface_name"/>
              <arg type="a{sv}" name="changed_properties"/>
              <arg type="as" name="invalidated_properties"/>
             </signal>
            </interface>
            <interface name="org.freedesktop.systemd.VtableExample">
             <method name="Method1">
              <arg type="s" direction="in"/>
              <arg type="s" direction="out"/>
             </method>
             <method name="Method2">
              <arg type="s" name="string" direction="in"/>
              <arg type="o" name="path" direction="in"/>
              <arg type="s" name="returnstring" direction="out"/>
              <annotation name="org.freedesktop.DBus.Deprecated" value="true"/>
             </method>
             <property name="AutomaticStringProperty" type="s" access="readwrite">
             </property>
             <property name="AutomaticIntegerProperty" type="u" access="readwrite">
              <annotation name="org.freedesktop.DBus.Property.EmitsChangedSignal" value="invalidates"/>
             </property>
            </interface>
           </node>

RETURN VALUE         top

       On success, sd_bus_add_object_vtable() and
       sd_bus_add_fallback_vtable() return a non-negative integer. On
       failure, they return a negative errno-style error code.

   Errors
       Returned errors may indicate the following problems:

       -EINVAL
           One of the required parameters is NULL or invalid. A reserved
           D-Bus interface was passed as the interface parameter.

       -ENOPKG
           The bus cannot be resolved.

       -ECHILD
           The bus was created in a different process, library or module
           instance.

       -ENOMEM
           Memory allocation failed.

       -EPROTOTYPE
           sd_bus_add_object_vtable() and sd_bus_add_fallback_vtable()
           have been both called for the same bus object path, which is
           not allowed.

       -EEXIST
           This vtable has already been registered for this interface and
           path.

NOTES         top

       Functions described here are available as a shared library, which
       can be compiled against and linked to with the
       libsystemd pkg-config(1) file.

       The code described here uses getenv(3), which is declared to be
       not multi-thread-safe. This means that the code calling the
       functions described here must not call setenv(3) from a parallel
       thread. It is recommended to only do calls to setenv() from an
       early phase of the program when no other threads have been
       started.

HISTORY         top

       sd_bus_property_get_t(), sd_bus_property_set_t(),
       sd_bus_object_find_t(), sd_bus_add_object(),
       sd_bus_add_fallback(), sd_bus_add_object_vtable(),
       sd_bus_add_fallback_vtable(), and sd_bus_add_filter() were added
       in version 221.

SEE ALSO         top

       sd-bus(3), busctl(1), sd_bus_emit_properties_changed(3),
       sd_bus_emit_object_added(3)

NOTES         top

        1. D-Bus annotations
           https://dbus.freedesktop.org/doc/dbus-specification.html#introspection-format

        2. polkit
           https://www.freedesktop.org/software/polkit/docs/latest/

COLOPHON         top

       This page is part of the systemd (systemd system and service
       manager) project.  Information about the project can be found at
       ⟨http://www.freedesktop.org/wiki/Software/systemd⟩.  If you have a
       bug report for this manual page, see
       ⟨http://www.freedesktop.org/wiki/Software/systemd/#bugreports⟩.
       This page was obtained from the project's upstream Git repository
       ⟨https://github.com/systemd/systemd.git⟩ on 2025-02-02.  (At that
       time, the date of the most recent commit that was found in the
       repository was 2025-02-02.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there is
       a better or more up-to-date source for the page, or you have
       corrections or improvements to the information in this COLOPHON
       (which is not part of the original manual page), send a mail to
       man-pages@man7.org

systemd 258~devel                                    SD_BUS_ADD_OBJECT(3)

Pages that refer to this page: sd-bus(3)sd_bus_add_node_enumerator(3)sd_bus_add_object_manager(3)sd_bus_call(3)sd_bus_process(3)sd_bus_slot_set_userdata(3)systemd.directives(7)systemd.index(7)