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：
#cat print-unit-path.c#include#include #include #include #include #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\n", 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\".\n", 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#include #include #include 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\n", 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\n", 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\n", 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\n", 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\n", strerror(-r)); goto finish; } for (;;) { /* Process requests */ r = sd_bus_process(bus, NULL); if (r < 0) { fprintf(stderr, "Failed to process bus: %s\n", 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\n", strerror(-r)); goto finish; } }finish: sd_bus_slot_unref(slot); sd_bus_unref(bus); return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS;}