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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | NOTES | EXAMPLES | HISTORY | SEE ALSO | COLOPHON |
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SD_BUS_CALL_METHOD(3) sd_bus_call_method SD_BUS_CALL_METHOD(3)
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 call
#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_method(sd_bus *bus, const char *destination,
const char *path, const char *interface,
const char *member,
sd_bus_error *ret_error,
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 *ret_error,
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);
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),
sd_bus_message_append(3) and sd_bus_call(3) 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), sd_bus_message_append(3) and
sd_bus_call_async(3) functions into a single function call.
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.
Functions described here are available as a shared library, which
can be compiled against and linked to with the
libsystemd pkg-config(1) file.
All functions listed here are thread-agnostic and only a single
thread may operate on a given object at any given time. Different
threads may access the same object at different times. Multiple
independent objects may be used from different threads in
parallel.
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.
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 $$
*
* 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.
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.
systemd(1), sd-bus(3), sd_bus_message_new_method_call(3),
sd_bus_message_append(3), sd_bus_call(3), sd_bus_set_property(3),
sd_bus_emit_signal(3)
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 2026-08-04. (At that
time, the date of the most recent commit that was found in the
repository was 2026-08-03.) 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 262~devel SD_BUS_CALL_METHOD(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)
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HTML rendering created 2026-09-09 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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