diff --git a/engine/engine.go b/engine/engine.go
index a68b0aa..1c9c5a2 100644
--- a/engine/engine.go
+++ b/engine/engine.go
@@ -2,20 +2,15 @@ package engine
 
 import (
 	"errors"
-	"fmt"
 	"net"
-	"os"
 
 	"github.com/xjasonlyu/tun2socks/v2/component/dialer"
 	"github.com/xjasonlyu/tun2socks/v2/core/device"
 	"github.com/xjasonlyu/tun2socks/v2/core/stack"
-	"github.com/xjasonlyu/tun2socks/v2/internal/version"
 	"github.com/xjasonlyu/tun2socks/v2/log"
 	"github.com/xjasonlyu/tun2socks/v2/proxy"
 	"github.com/xjasonlyu/tun2socks/v2/stats"
 	"github.com/xjasonlyu/tun2socks/v2/tunnel"
-
-	"gopkg.in/yaml.v3"
 )
 
 var _engine = &engine{}
@@ -45,8 +40,6 @@ type Key struct {
 	Device     string `yaml:"device"`
 	LogLevel   string `yaml:"loglevel"`
 	Interface  string `yaml:"interface"`
-	Config     string `yaml:"-"`
-	Version    bool   `yaml:"-"`
 }
 
 type engine struct {
@@ -62,22 +55,15 @@ func (e *engine) start() error {
 		return errors.New("empty key")
 	}
 
-	if e.Version {
-		fmt.Println(version.String())
-		fmt.Println(version.BuildString())
-		os.Exit(0)
-	}
-
 	for _, f := range []func() error{
-		e.setConfig,
-		e.setLogLevel,
-		e.setMark,
-		e.setInterface,
-		e.setStats,
-		e.setUDPTimeout,
-		e.setProxy,
-		e.setDevice,
-		e.setStack,
+		e.applyLogLevel,
+		e.applyMark,
+		e.applyInterface,
+		e.applyStats,
+		e.applyUDPTimeout,
+		e.applyProxy,
+		e.applyDevice,
+		e.applyStack,
 	} {
 		if err := f(); err != nil {
 			return err
@@ -97,19 +83,7 @@ func (e *engine) insert(k *Key) {
 	e.Key = k
 }
 
-func (e *engine) setConfig() error {
-	if e.Config == "" {
-		return nil
-	}
-
-	data, err := os.ReadFile(e.Config)
-	if err != nil {
-		return err
-	}
-	return yaml.Unmarshal(data, e.Key)
-}
-
-func (e *engine) setLogLevel() error {
+func (e *engine) applyLogLevel() error {
 	level, err := log.ParseLevel(e.LogLevel)
 	if err != nil {
 		return err
@@ -118,7 +92,7 @@ func (e *engine) setLogLevel() error {
 	return nil
 }
 
-func (e *engine) setMark() error {
+func (e *engine) applyMark() error {
 	if e.Mark != 0 {
 		dialer.SetMark(e.Mark)
 		log.Infof("[DIALER] set fwmark: %#x", e.Mark)
@@ -126,7 +100,7 @@ func (e *engine) setMark() error {
 	return nil
 }
 
-func (e *engine) setInterface() error {
+func (e *engine) applyInterface() error {
 	if e.Interface != "" {
 		if err := dialer.BindToInterface(e.Interface); err != nil {
 			return err
@@ -136,7 +110,7 @@ func (e *engine) setInterface() error {
 	return nil
 }
 
-func (e *engine) setStats() error {
+func (e *engine) applyStats() error {
 	if e.Stats != "" {
 		addr, err := net.ResolveTCPAddr("tcp", e.Stats)
 		if err != nil {
@@ -153,14 +127,14 @@ func (e *engine) setStats() error {
 	return nil
 }
 
-func (e *engine) setUDPTimeout() error {
+func (e *engine) applyUDPTimeout() error {
 	if e.UDPTimeout > 0 {
 		tunnel.SetUDPTimeout(e.UDPTimeout)
 	}
 	return nil
 }
 
-func (e *engine) setProxy() (err error) {
+func (e *engine) applyProxy() (err error) {
 	if e.Proxy == "" {
 		return errors.New("empty proxy")
 	}
@@ -170,7 +144,7 @@ func (e *engine) setProxy() (err error) {
 	return
 }
 
-func (e *engine) setDevice() (err error) {
+func (e *engine) applyDevice() (err error) {
 	if e.Device == "" {
 		return errors.New("empty device")
 	}
@@ -179,7 +153,7 @@ func (e *engine) setDevice() (err error) {
 	return
 }
 
-func (e *engine) setStack() (err error) {
+func (e *engine) applyStack() (err error) {
 	defer func() {
 		if err == nil {
 			log.Infof(
diff --git a/main.go b/main.go
index 0c80001..4861533 100644
--- a/main.go
+++ b/main.go
@@ -2,24 +2,32 @@ package main
 
 import (
 	"flag"
+	"fmt"
 	"os"
 	"os/signal"
 	"syscall"
 
 	"github.com/xjasonlyu/tun2socks/v2/engine"
+	"github.com/xjasonlyu/tun2socks/v2/internal/version"
 	"github.com/xjasonlyu/tun2socks/v2/log"
 
 	"go.uber.org/automaxprocs/maxprocs"
+	"gopkg.in/yaml.v3"
 )
 
-var key = new(engine.Key)
+var (
+	key = new(engine.Key)
+
+	configFile  string
+	versionFlag bool
+)
 
 func init() {
+	flag.BoolVar(&versionFlag, "version", false, "Show version and then quit")
 	flag.IntVar(&key.Mark, "fwmark", 0, "Set firewall MARK (Linux only)")
 	flag.IntVar(&key.MTU, "mtu", 0, "Set device maximum transmission unit (MTU)")
 	flag.IntVar(&key.UDPTimeout, "udp-timeout", 0, "Set timeout for each UDP session")
-	flag.BoolVar(&key.Version, "version", false, "Show version information and quit")
-	flag.StringVar(&key.Config, "config", "", "YAML format configuration file")
+	flag.StringVar(&configFile, "config", "", "YAML format configuration file")
 	flag.StringVar(&key.Device, "device", "", "Use this device [driver://]name")
 	flag.StringVar(&key.Interface, "interface", "", "Use network INTERFACE (Linux/MacOS only)")
 	flag.StringVar(&key.LogLevel, "loglevel", "info", "Log level [debug|info|warning|error|silent]")
@@ -32,16 +40,32 @@ func init() {
 func main() {
 	maxprocs.Set(maxprocs.Logger(func(string, ...any) {}))
 
+	if versionFlag {
+		fmt.Println(version.String())
+		fmt.Println(version.BuildString())
+		os.Exit(0)
+	}
+
+	if configFile != "" {
+		data, err := os.ReadFile(configFile)
+		if err != nil {
+			log.Fatalf("Failed to read config %s: %v", configFile, err)
+		}
+		if err = yaml.Unmarshal(data, key); err != nil {
+			log.Fatalf("Failed to unmarshal config %s: %v", configFile, err)
+		}
+	}
+
 	engine.Insert(key)
 
-	checkErr := func(msg string, f func() error) {
-		if err := f(); err != nil {
+	assert := func(msg string, err error) {
+		if err != nil {
 			log.Fatalf("Failed to %s: %v", msg, err)
 		}
 	}
 
-	checkErr("start engine", engine.Start)
-	defer checkErr("stop engine", engine.Stop)
+	assert("start engine", engine.Start())
+	defer assert("stop engine", engine.Stop())
 
 	sigCh := make(chan os.Signal, 1)
 	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)