sd-bus.h 例子
注意：
sd-dbus 是systemd提供的lib，但是这个lib，只有在systemd>v221版本后才可以使用，centos 219版本太低，所以不能使用。
参考： http://0pointer.net/blog/the-new-sd-bus-api-of-systemd.html
#cat print-unit-path.c
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <systemd/sd-bus.h>
#define _cleanup_(f) __attribute__((cleanup(f)))
/* This is equivalent to:
* busctl call org.freedesktop.systemd1 /org/freedesktop/systemd1
* org.freedesktop.systemd1.Manager GetUnitByPID $$
*
* Compile with 'cc -lsystemd print-unit-path.c'
*/
#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
", message, strerror(-error));
return error;
}
static int print_unit_path(sd_bus *bus) {
_cleanup_(sd_bus_message_unrefp) sd_bus_message *m = 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;
// create m
r = sd_bus_message_new_method_call(bus, &m,
DESTINATION, PATH, INTERFACE, MEMBER);
if (r < 0)
return log_error(r, "Failed to create bus message");
r = sd_bus_message_append(m, "u", (unsigned) getpid());
if (r < 0)
return log_error(r, "Failed to append to bus message");
r = sd_bus_call(bus, m, -1, &error, &reply);
if (r < 0)
return log_error(r, "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".
", ans);
return 0;
}
int main(int argc, char **argv) {
_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
int r;
/* Connect to the system bus */
r = sd_bus_open_system(&bus);
if (r < 0)
return log_error(r, "Failed to acquire bus");
print_unit_path(bus);
}
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <systemd/sd-bus.h>
static int method_multiply(sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
int64_t x, y;
int r;
/* Read the parameters */
r = sd_bus_message_read(m, "xx", &x, &y);
if (r < 0) {
fprintf(stderr, "Failed to parse parameters: %s
", strerror(-r));
return r;
}
/* Reply with the response */
return sd_bus_reply_method_return(m, "x", x * y);
}
static int method_divide(sd_bus_message *m, void *userdata, sd_bus_error *ret_error) {
int64_t x, y;
int r;
/* Read the parameters */
r = sd_bus_message_read(m, "xx", &x, &y);
if (r < 0) {
fprintf(stderr, "Failed to parse parameters: %s
", strerror(-r));
return r;
}
/* Return an error on division by zero */
if (y == 0) {
sd_bus_error_set_const(ret_error, "net.poettering.DivisionByZero", "Sorry, can't allow division by zero.");
return -EINVAL;
}
return sd_bus_reply_method_return(m, "x", x / y);
}
/* The vtable of our little object, implements the net.poettering.Calculator interface */
static const sd_bus_vtable calculator_vtable[] = {
SD_BUS_VTABLE_START(0),
SD_BUS_METHOD("Multiply", "xx", "x", method_multiply, SD_BUS_VTABLE_UNPRIVILEGED),
SD_BUS_METHOD("Divide", "xx", "x", method_divide, SD_BUS_VTABLE_UNPRIVILEGED),
SD_BUS_VTABLE_END
};
int main(int argc, char *argv[]) {
sd_bus_slot *slot = NULL;
sd_bus *bus = NULL;
int r;
/* Connect to the user bus this time */
r = sd_bus_open_user(&bus);
if (r < 0) {
fprintf(stderr, "Failed to connect to system bus: %s
", strerror(-r));
goto finish;
}
/* Install the object */
r = sd_bus_add_object_vtable(bus,
&slot,
"/net/poettering/Calculator", /* object path */
"net.poettering.Calculator", /* interface name */
calculator_vtable,
NULL);
if (r < 0) {
fprintf(stderr, "Failed to issue method call: %s
", strerror(-r));
goto finish;
}
/* Take a well-known service name so that clients can find us */
r = sd_bus_request_name(bus, "net.poettering.Calculator", 0);
if (r < 0) {
fprintf(stderr, "Failed to acquire service name: %s
", strerror(-r));
goto finish;
}
for (;;) {
/* Process requests */
r = sd_bus_process(bus, NULL);
if (r < 0) {
fprintf(stderr, "Failed to process bus: %s
", strerror(-r));
goto finish;
}
if (r > 0) /* we processed a request, try to process another one, right-away */
continue;
/* Wait for the next request to process */
r = sd_bus_wait(bus, (uint64_t) -1);
if (r < 0) {
fprintf(stderr, "Failed to wait on bus: %s
", strerror(-r));
goto finish;
}
}
finish:
sd_bus_slot_unref(slot);
sd_bus_unref(bus);
return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
}