x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_BUS_ADD_MATCH(3) sd_bus_add_match SD_BUS_ADD_MATCH(3)
NAME
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
SYNOPSIS
#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);
DESCRIPTION
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 each 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 similarly to sd_bus_add_match(),
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.
RETURN VALUE
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.
NOTES
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.
SEE ALSO
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)
NOTES
1. D-Bus Specification
https://dbus.freedesktop.org/doc/dbus-specification.html
systemd 254 SD_BUS_ADD_MATCH(3)
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