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https://github.com/systemd/systemd
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94ad70989f
Unfortunately, sd-bus-vtable.h, sd-journal.h, and sd-id128.h have variadic macro and inline initialization of sub-object, these are not supported in C90. So, we need to silence some errors.
252 lines
7.6 KiB
C
252 lines
7.6 KiB
C
/* SPDX-License-Identifier: MIT-0 */
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/* Implements the LogControl1 interface as per specification:
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* https://www.freedesktop.org/software/systemd/man/org.freedesktop.LogControl1.html
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*
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* Compile with 'cc logcontrol-example.c $(pkg-config --libs --cflags libsystemd)'
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*
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* To get and set properties via busctl:
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*
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* $ busctl --user get-property org.freedesktop.Example \
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* /org/freedesktop/LogControl1 \
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* org.freedesktop.LogControl1 \
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* SyslogIdentifier
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* s "example"
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* $ busctl --user get-property org.freedesktop.Example \
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* /org/freedesktop/LogControl1 \
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* org.freedesktop.LogControl1 \
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* LogTarget
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* s "journal"
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* $ busctl --user get-property org.freedesktop.Example \
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* /org/freedesktop/LogControl1 \
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* org.freedesktop.LogControl1 \
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* LogLevel
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* s "info"
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* $ busctl --user set-property org.freedesktop.Example \
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* /org/freedesktop/LogControl1 \
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* org.freedesktop.LogControl1 \
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* LogLevel \
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* "s" debug
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* $ busctl --user get-property org.freedesktop.Example \
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* /org/freedesktop/LogControl1 \
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* org.freedesktop.LogControl1 \
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* LogLevel
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* s "debug"
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*/
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#include <errno.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <syslog.h>
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#include <systemd/sd-bus.h>
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#include <systemd/sd-journal.h>
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#define _cleanup_(f) __attribute__((cleanup(f)))
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static int log_error(int log_level, int error, const char *str) {
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sd_journal_print(log_level, "%s failed: %s", str, strerror(-error));
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return error;
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}
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typedef enum LogTarget {
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LOG_TARGET_JOURNAL,
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LOG_TARGET_KMSG,
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LOG_TARGET_SYSLOG,
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LOG_TARGET_CONSOLE,
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_LOG_TARGET_MAX,
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} LogTarget;
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static const char* const log_target_table[_LOG_TARGET_MAX] = {
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[LOG_TARGET_JOURNAL] = "journal",
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[LOG_TARGET_KMSG] = "kmsg",
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[LOG_TARGET_SYSLOG] = "syslog",
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[LOG_TARGET_CONSOLE] = "console",
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};
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static const char* const log_level_table[LOG_DEBUG + 1] = {
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[LOG_EMERG] = "emerg",
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[LOG_ALERT] = "alert",
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[LOG_CRIT] = "crit",
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[LOG_ERR] = "err",
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[LOG_WARNING] = "warning",
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[LOG_NOTICE] = "notice",
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[LOG_INFO] = "info",
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[LOG_DEBUG] = "debug",
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};
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typedef struct object {
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const char *syslog_identifier;
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LogTarget log_target;
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int log_level;
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} object;
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static int property_get(
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sd_bus *bus,
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const char *path,
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const char *interface,
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const char *property,
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sd_bus_message *reply,
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void *userdata,
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sd_bus_error *error) {
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object *o = userdata;
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if (strcmp(property, "LogLevel") == 0)
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return sd_bus_message_append(reply, "s", log_level_table[o->log_level]);
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if (strcmp(property, "LogTarget") == 0)
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return sd_bus_message_append(reply, "s", log_target_table[o->log_target]);
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if (strcmp(property, "SyslogIdentifier") == 0)
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return sd_bus_message_append(reply, "s", o->syslog_identifier);
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return sd_bus_error_setf(error,
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SD_BUS_ERROR_UNKNOWN_PROPERTY,
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"Unknown property '%s'",
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property);
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}
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static int property_set(
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sd_bus *bus,
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const char *path,
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const char *interface,
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const char *property,
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sd_bus_message *message,
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void *userdata,
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sd_bus_error *error) {
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object *o = userdata;
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const char *value;
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int r;
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r = sd_bus_message_read(message, "s", &value);
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if (r < 0)
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return r;
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if (strcmp(property, "LogLevel") == 0) {
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int i;
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for (i = 0; i < LOG_DEBUG + 1; i++)
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if (strcmp(value, log_level_table[i]) == 0) {
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o->log_level = i;
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setlogmask(LOG_UPTO(i));
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return 0;
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}
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return sd_bus_error_setf(error,
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SD_BUS_ERROR_INVALID_ARGS,
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"Invalid value for LogLevel: '%s'",
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value);
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}
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if (strcmp(property, "LogTarget") == 0) {
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LogTarget i;
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for (i = 0; i < _LOG_TARGET_MAX; i++)
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if (strcmp(value, log_target_table[i]) == 0) {
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o->log_target = i;
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return 0;
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}
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return sd_bus_error_setf(error,
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SD_BUS_ERROR_INVALID_ARGS,
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"Invalid value for LogTarget: '%s'",
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value);
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}
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return sd_bus_error_setf(error,
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SD_BUS_ERROR_UNKNOWN_PROPERTY,
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"Unknown property '%s'",
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property);
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}
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/* https://www.freedesktop.org/software/systemd/man/sd_bus_add_object.html
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*/
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static const sd_bus_vtable vtable[] = {
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SD_BUS_VTABLE_START(0),
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SD_BUS_WRITABLE_PROPERTY(
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"LogLevel", "s",
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property_get, property_set,
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0,
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0),
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SD_BUS_WRITABLE_PROPERTY(
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"LogTarget", "s",
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property_get, property_set,
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0,
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0),
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SD_BUS_PROPERTY(
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"SyslogIdentifier", "s",
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property_get,
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0,
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SD_BUS_VTABLE_PROPERTY_CONST),
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SD_BUS_VTABLE_END
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};
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int main(int argc, char **argv) {
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/* The bus should be relinquished before the program terminates. The cleanup
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* attribute allows us to do it nicely and cleanly whenever we exit the
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* block.
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*/
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_cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
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object o = {
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.log_level = LOG_INFO,
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.log_target = LOG_TARGET_JOURNAL,
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.syslog_identifier = "example",
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};
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int r;
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/* https://man7.org/linux/man-pages/man3/setlogmask.3.html
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* Programs using syslog() instead of sd_journal can use this API to cut logs
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* emission at the source.
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*/
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setlogmask(LOG_UPTO(o.log_level));
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/* Acquire a connection to the bus, letting the library work out the details.
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* https://www.freedesktop.org/software/systemd/man/sd_bus_default.html
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*/
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r = sd_bus_default(&bus);
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if (r < 0)
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return log_error(o.log_level, r, "sd_bus_default()");
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/* Publish an interface on the bus, specifying our well-known object access
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* path and public interface name.
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* https://www.freedesktop.org/software/systemd/man/sd_bus_add_object.html
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* https://dbus.freedesktop.org/doc/dbus-tutorial.html
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*/
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r = sd_bus_add_object_vtable(bus, NULL,
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"/org/freedesktop/LogControl1",
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"org.freedesktop.LogControl1",
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vtable,
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&o);
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if (r < 0)
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return log_error(o.log_level, r, "sd_bus_add_object_vtable()");
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/* By default the service is assigned an ephemeral name. Also add a fixed
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* one, so that clients know whom to call.
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* https://www.freedesktop.org/software/systemd/man/sd_bus_request_name.html
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*/
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r = sd_bus_request_name(bus, "org.freedesktop.Example", 0);
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if (r < 0)
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return log_error(o.log_level, r, "sd_bus_request_name()");
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for (;;) {
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/* https://www.freedesktop.org/software/systemd/man/sd_bus_wait.html
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*/
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r = sd_bus_wait(bus, UINT64_MAX);
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if (r < 0)
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return log_error(o.log_level, r, "sd_bus_wait()");
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/* https://www.freedesktop.org/software/systemd/man/sd_bus_process.html
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*/
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r = sd_bus_process(bus, NULL);
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if (r < 0)
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return log_error(o.log_level, r, "sd_bus_process()");
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}
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/* https://www.freedesktop.org/software/systemd/man/sd_bus_release_name.html
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*/
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r = sd_bus_release_name(bus, "org.freedesktop.Example");
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if (r < 0)
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return log_error(o.log_level, r, "sd_bus_release_name()");
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return 0;
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}
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