DBus services
The message bus can start applications (services) on behalf of other applications, the application asks DBus to start a service by its name, usually the name should be known such as org.freedesktop.TextEditor.
In order for DBus to find the executable corresponding to a particular name, the bus daemon looks for service description files which usually are installed in /usr/share/dbus-1/services and they have .service in their extension name (all linux distros that i know they use this prefix to install dbus services files), as an example of a service file.
DBus service file example:
[D-BUS Service]
Name=org.share.linux
Exec=path to the executable.
We will write two programs, one is the service that we want to start the other is the application that activates this service
share-linux-serivce-example.c
#include <stdio.h>
#include <dbus/dbus.h>
int main()
{
DBusConnection *connection;
DBusError error;
dbus_error_init(&error);
connection = dbus_bus_get(DBUS_BUS_STARTER, &error); /* DBUS_BUS_STARTER is
the bus that started us */
/* Do something here to make sure that the application was successfully
started by DBus
* Example could be something like
* FILE *tmp;
* tmp = fopen("/tmp/share-linux-service.result", "w");
* fprintf(tmp,"share-linux service was started successfully");
* fclose(tmp);
* /
/* After that you have the service up, so you can do whetever you like */
dbus_connection_unref(connection);
return 0;
}
Compile this example with dbus-1 argument for pkg-config, you need to install the service file in /usr/share/dbus-1/service, name it org.share.linux and edit the
Exec path to where you have the service example binary.
start-service.c
#include <stdio.h>
#include <dbus/dbus.h>int main()
{
DBusConnection *connection;
DBusError error;
DBusMessage *message;
const char *service_name = "org.share.linux";
dbus_uint32_t flag; /* Currently this is not used by DBus, they say it is for
futur expansion*/
dbus_bool_t result;
dbus_error_init(&error);
connection = dbus_bus_get(DBUS_BUS_SESSION, &error);
if ( dbus_error_is_set(&error) )
{
printf("Error getting dbus connection: %s\n",error.message);
dbus_error_free(&error);
dbus_connection_unref(connection);
return 0;
}
message = dbus_message_new_method_call("org.freedesktop.DBus",
"/org/freedesktop/DBus",
"org.freedesktop.DBus",
"StartServiceByName");
if ( !message )
{
printf("Error creating DBus message\n");
dbus_connection_unref(connection);
return 0;
}
dbus_message_set_no_reply(message, TRUE); /* We don't want to receive a reply
*/
/* Append the argument to the message, must ends with DBUS_TYPE_UINT32 */
dbus_message_append_args(message,
DBUS_TYPE_STRING,
&service_name,
DBUS_TYPE_UINT32,
&flag,
DBUS_TYPE_INVALID);
result = dbus_connection_send(connection, message, NULL);
if ( result == TRUE )
{
printf("Successfully activating the %s service\n",service_name);
}
else
{
printf("Failed to activate the %s service\n",service_name);
}
dbus_message_unref(message);
dbus_connection_unref(connection);
return 0;
}
http://linoxide.com/how-tos/d-bus-ipc-mechanism-linux/