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v261
man/logcontrol-example.c
251 строка
8 KB
Jan Engelhardt
man: grammar fixes for introductory adverbs/phrases
25 дек 2024, 19:24
25 дек 2024, 19:24
c592ebd
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/* SPDX-License-Identifier: MIT-0 */ /* Implements the LogControl1 interface as per specification: * https://www.freedesktop.org/software/systemd/man/org.freedesktop.LogControl1.html * * Compile with 'cc logcontrol-example.c $(pkg-config --libs --cflags libsystemd)' * * To get and set properties via busctl: * * $ busctl --user get-property org.freedesktop.Example \ * /org/freedesktop/LogControl1 \ * org.freedesktop.LogControl1 \ * SyslogIdentifier * s "example" * $ busctl --user get-property org.freedesktop.Example \ * /org/freedesktop/LogControl1 \ * org.freedesktop.LogControl1 \ * LogTarget * s "journal" * $ busctl --user get-property org.freedesktop.Example \ * /org/freedesktop/LogControl1 \ * org.freedesktop.LogControl1 \ * LogLevel * s "info" * $ busctl --user set-property org.freedesktop.Example \ * /org/freedesktop/LogControl1 \ * org.freedesktop.LogControl1 \ * LogLevel \ * "s" debug * $ busctl --user get-property org.freedesktop.Example \ * /org/freedesktop/LogControl1 \ * org.freedesktop.LogControl1 \ * LogLevel * s "debug" */ #include <errno.h> #include <stdlib.h> #include <stdio.h> #include <syslog.h> #include <systemd/sd-bus.h> #include <systemd/sd-journal.h> #define _cleanup_(f) __attribute__((cleanup(f))) static int log_error(int log_level, int error, const char *str) { sd_journal_print(log_level, "%s failed: %s", str, strerror(-error)); return error; } typedef enum LogTarget { LOG_TARGET_JOURNAL, LOG_TARGET_KMSG, LOG_TARGET_SYSLOG, LOG_TARGET_CONSOLE, _LOG_TARGET_MAX, } LogTarget; static const char* const log_target_table[_LOG_TARGET_MAX] = { [LOG_TARGET_JOURNAL] = "journal", [LOG_TARGET_KMSG] = "kmsg", [LOG_TARGET_SYSLOG] = "syslog", [LOG_TARGET_CONSOLE] = "console", }; static const char* const log_level_table[LOG_DEBUG + 1] = { [LOG_EMERG] = "emerg", [LOG_ALERT] = "alert", [LOG_CRIT] = "crit", [LOG_ERR] = "err", [LOG_WARNING] = "warning", [LOG_NOTICE] = "notice", [LOG_INFO] = "info", [LOG_DEBUG] = "debug", }; typedef struct object { const char *syslog_identifier; LogTarget log_target; int log_level; } object; static int property_get( sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *reply, void *userdata, sd_bus_error *error) { object *o = userdata; if (strcmp(property, "LogLevel") == 0) return sd_bus_message_append(reply, "s", log_level_table[o->log_level]); if (strcmp(property, "LogTarget") == 0) return sd_bus_message_append(reply, "s", log_target_table[o->log_target]); if (strcmp(property, "SyslogIdentifier") == 0) return sd_bus_message_append(reply, "s", o->syslog_identifier); return sd_bus_error_setf(error, SD_BUS_ERROR_UNKNOWN_PROPERTY, "Unknown property '%s'", property); } static int property_set( sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *message, void *userdata, sd_bus_error *error) { object *o = userdata; const char *value; int r; r = sd_bus_message_read(message, "s", &value); if (r < 0) return r; if (strcmp(property, "LogLevel") == 0) { int i; for (i = 0; i < LOG_DEBUG + 1; i++) if (strcmp(value, log_level_table[i]) == 0) { o->log_level = i; setlogmask(LOG_UPTO(i)); return 0; } return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid value for LogLevel: '%s'", value); } if (strcmp(property, "LogTarget") == 0) { LogTarget i; for (i = 0; i < _LOG_TARGET_MAX; i++) if (strcmp(value, log_target_table[i]) == 0) { o->log_target = i; return 0; } return sd_bus_error_setf(error, SD_BUS_ERROR_INVALID_ARGS, "Invalid value for LogTarget: '%s'", value); } return sd_bus_error_setf(error, SD_BUS_ERROR_UNKNOWN_PROPERTY, "Unknown property '%s'", property); } /* https://www.freedesktop.org/software/systemd/man/sd_bus_add_object.html */ static const sd_bus_vtable vtable[] = { SD_BUS_VTABLE_START(0), SD_BUS_WRITABLE_PROPERTY( "LogLevel", "s", property_get, property_set, 0, 0), SD_BUS_WRITABLE_PROPERTY( "LogTarget", "s", property_get, property_set, 0, 0), SD_BUS_PROPERTY( "SyslogIdentifier", "s", property_get, 0, SD_BUS_VTABLE_PROPERTY_CONST), SD_BUS_VTABLE_END }; int main(int argc, char **argv) { /* The bus should be relinquished before the program terminates. The cleanup * attribute allows us to do it nicely and cleanly whenever we exit the * block. */ _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL; object o = { .log_level = LOG_INFO, .log_target = LOG_TARGET_JOURNAL, .syslog_identifier = "example", }; int r; /* https://man7.org/linux/man-pages/man3/setlogmask.3.html * Programs using syslog() instead of sd_journal can use this API to cut logs * emission at the source. */ setlogmask(LOG_UPTO(o.log_level)); /* Acquire a connection to the bus, letting the library work out the details. * https://www.freedesktop.org/software/systemd/man/sd_bus_default.html */ r = sd_bus_default(&bus); if (r < 0) return log_error(o.log_level, r, "sd_bus_default()"); /* Publish an interface on the bus, specifying our well-known object access * path and public interface name. * https://www.freedesktop.org/software/systemd/man/sd_bus_add_object.html * https://dbus.freedesktop.org/doc/dbus-tutorial.html */ r = sd_bus_add_object_vtable(bus, NULL, "/org/freedesktop/LogControl1", "org.freedesktop.LogControl1", vtable, &o); if (r < 0) return log_error(o.log_level, r, "sd_bus_add_object_vtable()"); /* By default, the service is assigned an ephemeral name. Also add a fixed * one, so that clients know whom to call. * https://www.freedesktop.org/software/systemd/man/sd_bus_request_name.html */ r = sd_bus_request_name(bus, "org.freedesktop.Example", 0); if (r < 0) return log_error(o.log_level, r, "sd_bus_request_name()"); for (;;) { /* https://www.freedesktop.org/software/systemd/man/sd_bus_wait.html */ r = sd_bus_wait(bus, UINT64_MAX); if (r < 0) return log_error(o.log_level, r, "sd_bus_wait()"); /* https://www.freedesktop.org/software/systemd/man/sd_bus_process.html */ r = sd_bus_process(bus, NULL); if (r < 0) return log_error(o.log_level, r, "sd_bus_process()"); } /* https://www.freedesktop.org/software/systemd/man/sd_bus_release_name.html */ r = sd_bus_release_name(bus, "org.freedesktop.Example"); if (r < 0) return log_error(o.log_level, r, "sd_bus_release_name()"); return 0; }