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NAME |SYNOPSIS |DESCRIPTION |RETURN VALUE |NOTES |EXAMPLES |HISTORY |SEE ALSO |COLOPHON | |
SD_BUS_CALL_METHOD(3) sd_bus_call_methodSD_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_listap);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_tcallback,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_tcallback,void *userdata, const char *types,va_listap);
sd_bus_call_method()is a convenience function for initializing a bus message object and calling the corresponding D-Bus method. It combines thesd_bus_message_new_method_call(3),sd_bus_message_append(3) andsd_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 thesd_bus_message_new_method_call(3),sd_bus_message_append(3) andsd_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 ofsd_bus_message_new_method_call(3),sd_bus_message_append(3),sd_bus_call(3) andsd_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 thelibsystemd pkg-config(1) file. The code described here usesgetenv(3), which is declared to be not multi-thread-safe. This means that the code calling the functions described here must not callsetenv(3) from a parallel thread. It is recommended to only do calls tosetenv()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 singleparameter /* 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(), andsd_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 thesystemd (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 isnot part of the original manual page), send a mail to man-pages@man7.orgsystemd 258~rc2SD_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)
HTML rendering created 2025-09-06 byMichael Kerrisk, author ofThe Linux Programming Interface. For details of in-depthLinux/UNIX system programming training courses that I teach, lookhere. Hosting byjambit GmbH. | |