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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.
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 2025-08-11. (At that
time, the date of the most recent commit that was found in the
repository was 2025-08-11.) 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
[email protected]
systemd 258~rc2 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 2025-09-06 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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