|
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | SEE ALSO | NOTES | COLOPHON |
SD_BUS_ADD_MATCH(3) sd_bus_add_match SD_BUS_ADD_MATCH(3)
sd_bus_add_match, sd_bus_add_match_async, sd_bus_match_signal,
sd_bus_match_signal_async - Add a match rule for incoming message
dispatching
#include <systemd/sd-bus.h>
typedef int (*sd_bus_message_handler_t)(sd_bus_message *m,
void *userdata,
sd_bus_error *ret_error);
int sd_bus_add_match(sd_bus *bus, sd_bus_slot **slot,
const char *match,
sd_bus_message_handler_t callback,
void *userdata);
int sd_bus_add_match_async(sd_bus *bus, sd_bus_slot **slot,
const char *match,
sd_bus_message_handler_t callback,
sd_bus_message_handler_t install_callback,
void *userdata);
int sd_bus_match_signal(sd_bus *bus, sd_bus_slot **slot,
const char *sender, const char *path,
const char *interface, const char *member,
sd_bus_message_handler_t callback,
void *userdata);
int sd_bus_match_signal_async(sd_bus *bus, sd_bus_slot **slot,
const char *sender, const char *path,
const char *interface,
const char *member,
sd_bus_message_handler_t callback,
sd_bus_message_handler_t install_callback,
void *userdata);
sd_bus_add_match() installs a match rule for messages received on the
specified bus connection object bus. The syntax of the match rule
expression passed in match is described in the D-Bus
Specification[1]. The specified handler function callback is called
for eaching incoming message matching the specified expression, the
userdata parameter is passed as-is to the callback function. The
match is installed synchronously when connected to a bus broker, i.e.
the call sends a control message requested the match to be added to
the broker and waits until the broker confirms the match has been
installed successfully.
sd_bus_add_match_async() operates very similar to
sd_bus_match_signal(), however it installs the match asynchronously,
in a non-blocking fashion: a request is sent to the broker, but the
call does not wait for a response. The install_callback function is
called when the response is later received, with the response message
from the broker as parameter. If this function is specified as NULL a
default implementation is used that terminates the bus connection
should installing the match fail.
sd_bus_match_signal() is very similar to sd_bus_add_match(), but only
matches signals, and instead of a match expression accepts four
parameters: sender (the service name of the sender), path (the object
path of the emitting object), interface (the interface the signal
belongs to), member (the signal name), from which the match string is
internally generated. Optionally, these parameters may be specified
as NULL in which case the relevant field of incoming signals is not
tested.
sd_bus_match_signal_async() combines the signal matching logic of
sd_bus_match_signal() with the asynchronous behaviour of
sd_bus_add_match_async().
On success, and if non-NULL, the slot return parameter will be set to
a slot object that may be used as a reference to the installed match,
and may be utilized to remove it again at a later time with
sd_bus_slot_unref(3). If specified as NULL the lifetime of the match
is bound to the lifetime of the bus object itself, and the match is
generally not removed independently. See sd_bus_slot_set_floating(3)
for details.
The message m passed to the callback is only borrowed, that is, the
callback should not call sd_bus_message_unref(3) on it. If the
callback wants to hold on to the message beyond the lifetime of the
callback, it needs to call sd_bus_message_ref(3) to create a new
reference.
If an error occurs during the callback invocation, the callback
should return a negative error number (optionally, a more precise
error may be returned in ret_error, as well). If it wants other
callbacks that match the same rule to be called, it should return 0.
Otherwise it should return a positive integer.
If the bus refers to a direct connection (i.e. not a bus connection,
as set with sd_bus_set_bus_client(3)) the match is only installed on
the client side, and the synchronous and asynchronous functions
operate the same.
On success, sd_bus_add_match() and the other calls return 0 or a
positive integer. On failure, they return a negative errno-style
error code.
These APIs are implemented as a shared library, which can be compiled
and linked to with the libsystemd pkg-config(1) file.
systemd(1), sd-bus(3), sd_bus_slot_unref(3), sd_bus_message_ref(3),
sd_bus_set_bus_client(3), sd_bus_slot_set_floating(3)
1. D-Bus Specification
https://dbus.freedesktop.org/doc/dbus-specification.html
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 2020-08-13. (At that
time, the date of the most recent commit that was found in the repos‐
itory was 2020-08-11.) 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 246 SD_BUS_ADD_MATCH(3)
Pages that refer to this page: sd_bus_get_watch_bind(3) , sd_bus_set_watch_bind(3) , 30-systemd-environment-d-generator(7) , systemd.index(7)