diff --git a/src/cleardns.c b/src/cleardns.c
index 2199168..1902bc9 100644
--- a/src/cleardns.c
+++ b/src/cleardns.c
@@ -2,6 +2,7 @@
 #include <stdlib.h>
 #include <time.h>
 #include <unistd.h>
+#include <string.h>
 #include "loader.h"
 #include "logger.h"
 #include "constant.h"
@@ -11,11 +12,7 @@
 #include "adguard.h"
 #include "system.h"
 #include "assets.h"
-
-//#include <stdio.h>
-//#include <string.h>
-//#include "common.h"
-//#include "process.h"
+#include "sundry.h"
 
 //char *init_script = "/usr/bin/load";
 //char *custom_script = "/etc/cleardns/custom.sh";
@@ -24,48 +21,63 @@
 //char *overture_config = "/etc/overture/config.yml";
 //char *upstream_config = "/etc/cleardns/upstream.json";
 
-//void show_command(char *title, char **command) {
-//    int num = 0;
-//    fprintf(stderr, "%s => \"", title);
-//    while(command[num] != NULL) {
-//        fprintf(stderr, "%s", command[num++]);
-//        if (command[num] != NULL) {
-//            fprintf(stderr, " ");
-//        }
-//    }
-//    fprintf(stderr, "\"\n");
-//}
+#define HELP_MSG "\
+ClearDNS usage \n\
+--debug ...\n\
+--config ...\n\
+--help ...\n\
+"
 
-// TODO: load `--debug`, `--config ...`, `--version`
+#define CONFIG_FILE "test.json"
 
-int main(int argc, char *argv[]) { // ClearDNS server
+// TODO: load `--debug`, `--config ...`, `--version`, `--help`
 
-    LOG_LEVEL = LOG_DEBUG;
-    log_info("ClearDNS server start (%s)", VERSION);
+char* init(int argc, char *argv[]) { // return config file
+    char *config = string_init(CONFIG_FILE);
+    for (int i = 0; i < argc; ++i) {
+        if (!strcmp(argv[i], "--debug")) {
+            LOG_LEVEL = LOG_DEBUG; // enable debug mode
+        }
+        if (!strcmp(argv[i], "--version")) {
+            printf("ClearDNS version %s\n", VERSION); // show version
+            exit(0);
+        }
+        if (!strcmp(argv[i], "--help")) {
+            printf("\n%s\n", HELP_MSG); // show help message
+            exit(0);
+        }
+        if (!strcmp(argv[i], "--config")) {
+            if (i + 1 == argc) {
+                log_error("Option `--config` missing value");
+                exit(1);
+            }
+            free(config);
+            config = string_init(argv[++i]); // use custom config file
+        }
+    }
+    log_debug("Config file -> %s", config);
+    return config;
+}
 
 
-    // TODO: load assets -> extract `/assets.tar.xz` -> ${ASSETS_DIR}*.txt
+int main(int argc, char *argv[]) { // ClearDNS server
 
-    load_assets();
-    return 0;
+    char *config_file = init(argc, argv);
 
+    LOG_LEVEL = LOG_DEBUG; // TODO: dev only
+    log_info("ClearDNS server start (%s)", VERSION);
 
-    load_config("test.json");
+    load_config(config_file);
+    free(config_file);
 
     dnsproxy_load("Domestic", loader.domestic, "domestic.json");
     dnsproxy_load("Foreign", loader.foreign, "foreign.json");
     overture_load(loader.diverter, "overture.json");
     adguard_load(loader.filter, ADGUARD_DIR);
 
+    // TODO: running custom script
+
 
-//    int debug_mode = 0;
-//    fprintf(stderr, "[ClearDNS] Server start.\n");
-//    for (char **p = argv; p < argv + argc; ++p) {
-//        if (!strcmp(*p, "--debug")) { // --debug option
-//            ++debug_mode;
-//        }
-//    }
-//
 //    init_server(init_script, custom_script); // run init script and custom script
 //
 //    load_start_command(adguard_workdir, overture_config, upstream_config, debug_mode); // generate commands