x SuSE Linux 13.1-RELEASE x
x SuSE Linux 13.1-RELEASEx
SD_BUS_CALL(3) sd_bus_call SD_BUS_CALL(3)
NAME
sd_bus_call, sd_bus_call_async - Invoke a D-Bus method call
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_call(sd_bus *bus, sd_bus_message *m, uint64_t usec,
sd_bus_error *ret_error, sd_bus_message **reply);
int sd_bus_call_async(sd_bus *bus, sd_bus_slot **slot,
sd_bus_message *m,
sd_bus_message_handler_t callback,
void *userdata, uint64_t usec);
DESCRIPTION
sd_bus_call() takes a complete bus message object and calls the
corresponding D-Bus method. On success, the response is stored in
reply. usec indicates the timeout in microseconds. If ret_error is not
NULL and sd_bus_call() fails (either because of an internal error or
because it received a D-Bus error reply), ret_error is initialized to
an instance of sd_bus_error describing the error.
sd_bus_call_async() is like sd_bus_call() but works asynchronously. The
callback indicates the function to call when the response arrives. The
userdata pointer will be passed to the callback function, and may be
chosen freely by the caller. If slot is not NULL and
sd_bus_call_async() succeeds, slot is set to a slot object which can be
used to cancel the method call at a later time using
sd_bus_slot_unref(3). If slot is NULL, the lifetime of the method call
is bound to the lifetime of the bus object itself, and it cannot be
cancelled independently. See sd_bus_slot_set_floating(3) for details.
callback is called when a reply arrives with the reply, userdata and an
sd_bus_error output parameter as its arguments. Unlike sd_bus_call(),
the sd_bus_error output parameter passed to the callback will be empty.
To determine whether the method call succeeded, use
sd_bus_message_is_method_error(3) on the reply message passed to the
callback instead. If the callback returns zero and the sd_bus_error
output parameter is still empty when the callback finishes, other
handlers registered with functions such as sd_bus_add_filter(3) or
sd_bus_add_match(3) are given a chance to process the message. If the
callback returns a non-zero value or the sd_bus_error output parameter
is not empty when the callback finishes, no further processing of the
message is done. Generally, you want to return zero from the callback
to give other registered handlers a chance to process the reply as
well. (Note that the sd_bus_error parameter is an output parameter of
the callback function, not an input parameter; it can be used to
propagate errors from the callback handler, it will not receive any
error that was received as method reply.)
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 usec is zero, the default D-Bus method call timeout is used. See
sd_bus_get_method_call_timeout(3).
RETURN VALUE
On success, these functions return a non-negative integer. On failure,
they return a negative errno-style error code.
Errors
When sd_bus_call() internally receives a D-Bus error reply, it will set
ret_error if it is not NULL, and will return a negative value mapped
from the error reply, see sd_bus_error_get_errno(3).
Returned errors may indicate the following problems:
-EINVAL
The input parameter m is NULL. The input parameter m is not a
D-Bus method call. To create a new D-Bus method call, use
sd_bus_message_new_method_call(3). The input parameter m has the
BUS_MESSAGE_NO_REPLY_EXPECTED flag set. The input parameter error
is non-NULL but was not set to SD_BUS_ERROR_NULL.
-ECHILD
The bus connection was allocated in a parent process and is being
reused in a child process after fork().
-ENOTCONN
The input parameter bus is NULL or the bus is not connected.
-ECONNRESET
The bus connection was closed while waiting for the response.
-ETIMEDOUT
A response was not received within the given timeout.
-ELOOP
The message m is addressed to its own client.
-ENOMEM
Memory allocation failed.
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_call_method(3),
sd_bus_call_method_async(3), sd_bus_message_new_method_call(3),
sd_bus_message_append(3), sd_bus_error(3)
systemd 254 SD_BUS_CALL(3)
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