sd_bus_call_method(3) - Linux manual page (original) (raw)
SDBUSCALLMETHOD(3) sd_bus_call_method SDBUSCALLMETHOD(3)
NAME top
sd_bus_call_method, sd_bus_call_methodv, sd_bus_call_method_async,
sd_bus_call_method_asyncv - Initialize a bus message object and
invoke the corresponding D-Bus method callSYNOPSIS top
**#include <systemd/sd-bus.h>**
**typedef int (*sd_bus_message_handler_t)(sd_bus_message ***_m_**,**
**void ***_userdata_**,**
**sd_bus_error ***_reterror_**);**
**int sd_bus_call_method(sd_bus ***_bus_**, const char ***_destination_**,**
**const char ***_path_**, const char ***_interface_**,**
**const char ***_member_**,**
**sd_bus_error ***_reterror_**,**
**sd_bus_message** _reply_**, const char ***_types_**,**
**...);**
**int sd_bus_call_methodv(sd_bus ***_bus_**, const char ***_destination_**,**
**const char ***_path_**, const char ***_interface_**,**
**const char ***_member_**,**
**sd_bus_error ***_reterror_**,**
**sd_bus_message** _reply_**, const char ***_types_**,**
**va_list** _ap_**);**
**int sd_bus_call_method_async(sd_bus ***_bus_**, sd_bus_slot** _slot_**,**
**const char ***_destination_**,**
**const char ***_path_**,**
**const char ***_interface_**,**
**const char ***_member_**,**
**sd_bus_message_handler_t** _callback_**,**
**void ***_userdata_**, const char ***_types_**,**
**...);**
**int sd_bus_call_method_asyncv(sd_bus ***_bus_**, sd_bus_slot** _slot_**,**
**const char ***_destination_**,**
**const char ***_path_**,**
**const char ***_interface_**,**
**const char ***_member_**,**
**sd_bus_message_handler_t** _callback_**,**
**void ***_userdata_**, const char ***_types_**,**
**va_list** _ap_**);**DESCRIPTION top
**sd_bus_call_method()** is a convenience function for initializing a
bus message object and calling the corresponding D-Bus method. It
combines the [sd_bus_message_new_method_call(3)](../man3/sd%5Fbus%5Fmessage%5Fnew%5Fmethod%5Fcall.3.html),
[sd_bus_message_append(3)](../man3/sd%5Fbus%5Fmessage%5Fappend.3.html) and [sd_bus_call(3)](../man3/sd%5Fbus%5Fcall.3.html) functions into a
single function call.
**sd_bus_call_method_async()** is a convenience function for
initializing a bus message object and calling the corresponding
D-Bus method asynchronously. It combines the
[sd_bus_message_new_method_call(3)](../man3/sd%5Fbus%5Fmessage%5Fnew%5Fmethod%5Fcall.3.html), [sd_bus_message_append(3)](../man3/sd%5Fbus%5Fmessage%5Fappend.3.html) and
[sd_bus_call_async(3)](../man3/sd%5Fbus%5Fcall%5Fasync.3.html) functions into a single function call.RETURN VALUE top
On success, these functions return a non-negative integer. On
failure, they return a negative errno-style error code.Errors See the man pages of sd_bus_message_new_method_call(3), sd_bus_message_append(3), sd_bus_call(3) and sd_bus_call_async(3) for a list of possible errors.
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)](../man3/getenv.3.html), which is declared to be
not multi-thread-safe. This means that the code calling the
functions described here must not call [setenv(3)](../man3/setenv.3.html) 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.EXAMPLES top
**Example 1. Make a call to a D-Bus method that takes a single**
**parameter**
/* SPDX-License-Identifier: MIT-0 */
/* This is equivalent to:
* busctl call org.freedesktop.systemd1 /org/freedesktop/systemd1 \
* org.freedesktop.systemd1.Manager GetUnitByPID <span class="katex"><span class="katex-mathml"><math xmlns="http://www.w3.org/1998/Math/MathML"><semantics><mrow></mrow><annotation encoding="application/x-tex"></annotation></semantics></math></span><span class="katex-html" aria-hidden="true"></span></span>
*
* Compile with 'cc print-unit-path-call-method.c -lsystemd'
*/
#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <systemd/sd-bus.h>
#define _cleanup_(f) __attribute__((cleanup(f)))
#define DESTINATION "org.freedesktop.systemd1"
#define PATH "/org/freedesktop/systemd1"
#define INTERFACE "org.freedesktop.systemd1.Manager"
#define MEMBER "GetUnitByPID"
static int log_error(int error, const char *message) {
fprintf(stderr, "%s: %s\n", message, strerror(-error));
return error;
}
int main(int argc, char **argv) {
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
_cleanup_(sd_bus_error_free) sd_bus_error error = SD_BUS_ERROR_NULL;
_cleanup_(sd_bus_message_unrefp) sd_bus_message *reply = NULL;
int r;
r = sd_bus_open_system(&bus);
if (r < 0)
return log_error(r, "Failed to acquire bus");
r = sd_bus_call_method(bus, DESTINATION, PATH, INTERFACE, MEMBER, &error, &reply, "u", (unsigned) getpid());
if (r < 0)
return log_error(r, MEMBER " call failed");
const char *ans;
r = sd_bus_message_read(reply, "o", &ans);
if (r < 0)
return log_error(r, "Failed to read reply");
printf("Unit path is \"%s\".\n", ans);
return 0;
}
This defines a minimally useful program that will open a
connection to the bus, call a method, wait for the reply, and
finally extract and print the answer. It does error handling and
proper memory management.HISTORY top
**sd_bus_call_method()**, and **sd_bus_call_method_async()** were added in
version 221.
**sd_bus_call_methodv()**, **sd_bus_call_method_asyncv()** were added in
version 246.SEE ALSO top
[systemd(1)](../man1/systemd.1.html), [sd-bus(3)](../man3/sd-bus.3.html), [sd_bus_message_new_method_call(3)](../man3/sd%5Fbus%5Fmessage%5Fnew%5Fmethod%5Fcall.3.html),
[sd_bus_message_append(3)](../man3/sd%5Fbus%5Fmessage%5Fappend.3.html), [sd_bus_call(3)](../man3/sd%5Fbus%5Fcall.3.html), [sd_bus_set_property(3)](../man3/sd%5Fbus%5Fset%5Fproperty.3.html),
[sd_bus_emit_signal(3)](../man3/sd%5Fbus%5Femit%5Fsignal.3.html)COLOPHON top
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(which is _not_ part of the original manual page), send a mail to
man-pages@man7.orgsystemd 258~devel SDBUSCALLMETHOD(3)
Pages that refer to this page:sd-bus(3), sd_bus_call(3), sd_bus_emit_signal(3), sd_bus_interface_name_is_valid(3), sd_bus_message_new_method_call(3), sd_bus_send(3), sd_bus_set_property(3), sd_bus_slot_ref(3), systemd.directives(7), systemd.index(7)