cmd/*: refactor get flag value

cmd/devp2p/enrcmd.go

@@ -34,18 +34,20 @@ import (
 	"gopkg.in/urfave/cli.v1"
 )
 
+var fileFlag = cli.StringFlag{Name: "file"}
+
 var enrdumpCommand = cli.Command{
 	Name:   "enrdump",
 	Usage:  "Pretty-prints node records",
 	Action: enrdump,
 	Flags: []cli.Flag{
-		cli.StringFlag{Name: "file"},
+		fileFlag,
 	},
 }
 
 func enrdump(ctx *cli.Context) error {
 	var source string
-	if file := ctx.String("file"); file != "" {
+	if file := ctx.String(fileFlag.Name); file != "" {
 		if ctx.NArg() != 0 {
 			return fmt.Errorf("can't dump record from command-line argument in -file mode")
 		}

cmd/ethkey/generate.go

@@ -35,6 +35,17 @@ type outputGenerate struct {
 	AddressEIP55 string
 }
 
+var (
+	privateKeyFlag = cli.StringFlag{
+		Name:  "privatekey",
+		Usage: "file containing a raw private key to encrypt",
+	}
+	lightKDFFlag = cli.BoolFlag{
+		Name:  "lightkdf",
+		Usage: "use less secure scrypt parameters",
+	}
+)
+
 var commandGenerate = cli.Command{
 	Name:      "generate",
 	Usage:     "generate new keyfile",
@@ -48,14 +59,8 @@ If you want to encrypt an existing private key, it can be specified by setting
 	Flags: []cli.Flag{
 		passphraseFlag,
 		jsonFlag,
-		cli.StringFlag{
-			Name:  "privatekey",
-			Usage: "file containing a raw private key to encrypt",
-		},
-		cli.BoolFlag{
-			Name:  "lightkdf",
-			Usage: "use less secure scrypt parameters",
-		},
+		privateKeyFlag,
+		lightKDFFlag,
 	},
 	Action: func(ctx *cli.Context) error {
 		// Check if keyfile path given and make sure it doesn't already exist.
@@ -71,7 +76,7 @@ If you want to encrypt an existing private key, it can be specified by setting
 
 		var privateKey *ecdsa.PrivateKey
 		var err error
-		if file := ctx.String("privatekey"); file != "" {
+		if file := ctx.String(privateKeyFlag.Name); file != "" {
 			// Load private key from file.
 			privateKey, err = crypto.LoadECDSA(file)
 			if err != nil {
@@ -99,7 +104,7 @@ If you want to encrypt an existing private key, it can be specified by setting
 		// Encrypt key with passphrase.
 		passphrase := getPassphrase(ctx, true)
 		scryptN, scryptP := keystore.StandardScryptN, keystore.StandardScryptP
-		if ctx.Bool("lightkdf") {
+		if ctx.Bool(lightKDFFlag.Name) {
 			scryptN, scryptP = keystore.LightScryptN, keystore.LightScryptP
 		}
 		keyjson, err := keystore.EncryptKey(key, passphrase, scryptN, scryptP)

cmd/ethkey/inspect.go

@@ -33,6 +33,13 @@ type outputInspect struct {
 	PrivateKey string
 }
 
+var (
+	privateFlag = cli.BoolFlag{
+		Name:  "private",
+		Usage: "include the private key in the output",
+	}
+)
+
 var commandInspect = cli.Command{
 	Name:      "inspect",
 	Usage:     "inspect a keyfile",
@@ -45,10 +52,7 @@ make sure to use this feature with great caution!`,
 	Flags: []cli.Flag{
 		passphraseFlag,
 		jsonFlag,
-		cli.BoolFlag{
-			Name:  "private",
-			Usage: "include the private key in the output",
-		},
+		privateFlag,
 	},
 	Action: func(ctx *cli.Context) error {
 		keyfilepath := ctx.Args().First()
@@ -67,7 +71,7 @@ make sure to use this feature with great caution!`,
 		}
 
 		// Output all relevant information we can retrieve.
-		showPrivate := ctx.Bool("private")
+		showPrivate := ctx.Bool(privateFlag.Name)
 		out := outputInspect{
 			Address: key.Address.Hex(),
 			PublicKey: hex.EncodeToString(

cmd/ethkey/message.go

@@ -142,7 +142,7 @@ It is possible to refer to a file containing the message.`,
 }
 
 func getMessage(ctx *cli.Context, msgarg int) []byte {
-	if file := ctx.String("msgfile"); file != "" {
+	if file := ctx.String(msgfileFlag.Name); file != "" {
 		if len(ctx.Args()) > msgarg {
 			utils.Fatalf("Can't use --msgfile and message argument at the same time.")
 		}

cmd/p2psim/main.go

@@ -56,19 +56,58 @@ import (
 
 var client *simulations.Client
 
+var (
+	// global command flags
+	apiFlag = cli.StringFlag{
+		Name:   "api",
+		Value:  "http://localhost:8888",
+		Usage:  "simulation API URL",
+		EnvVar: "P2PSIM_API_URL",
+	}
+
+	// events subcommand flags
+	currentFlag = cli.BoolFlag{
+		Name:  "current",
+		Usage: "get existing nodes and conns first",
+	}
+	filterFlag = cli.StringFlag{
+		Name:  "filter",
+		Value: "",
+		Usage: "message filter",
+	}
+
+	// node create subcommand flags
+	nameFlag = cli.StringFlag{
+		Name:  "name",
+		Value: "",
+		Usage: "node name",
+	}
+	servicesFlag = cli.StringFlag{
+		Name:  "services",
+		Value: "",
+		Usage: "node services (comma separated)",
+	}
+	keyFlag = cli.StringFlag{
+		Name:  "key",
+		Value: "",
+		Usage: "node private key (hex encoded)",
+	}
+
+	// node rpc subcommand flags
+	subscribeFlag = cli.BoolFlag{
+		Name:  "subscribe",
+		Usage: "method is a subscription",
+	}
+)
+
 func main() {
 	app := cli.NewApp()
 	app.Usage = "devp2p simulation command-line client"
 	app.Flags = []cli.Flag{
-		cli.StringFlag{
-			Name:   "api",
-			Value:  "http://localhost:8888",
-			Usage:  "simulation API URL",
-			EnvVar: "P2PSIM_API_URL",
-		},
+		apiFlag,
 	}
 	app.Before = func(ctx *cli.Context) error {
-		client = simulations.NewClient(ctx.GlobalString("api"))
+		client = simulations.NewClient(ctx.GlobalString(apiFlag.Name))
 		return nil
 	}
 	app.Commands = []cli.Command{
@@ -82,15 +121,8 @@ func main() {
 			Usage:  "stream network events",
 			Action: streamNetwork,
 			Flags: []cli.Flag{
-				cli.BoolFlag{
-					Name:  "current",
-					Usage: "get existing nodes and conns first",
-				},
-				cli.StringFlag{
-					Name:  "filter",
-					Value: "",
-					Usage: "message filter",
-				},
+				currentFlag,
+				filterFlag,
 			},
 		},
 		{
@@ -118,21 +150,9 @@ func main() {
 					Usage:  "create a node",
 					Action: createNode,
 					Flags: []cli.Flag{
-						cli.StringFlag{
-							Name:  "name",
-							Value: "",
-							Usage: "node name",
-						},
-						cli.StringFlag{
-							Name:  "services",
-							Value: "",
-							Usage: "node services (comma separated)",
-						},
-						cli.StringFlag{
-							Name:  "key",
-							Value: "",
-							Usage: "node private key (hex encoded)",
-						},
+						nameFlag,
+						servicesFlag,
+						keyFlag,
 					},
 				},
 				{
@@ -171,10 +191,7 @@ func main() {
 					Usage:     "call a node RPC method",
 					Action:    rpcNode,
 					Flags: []cli.Flag{
-						cli.BoolFlag{
-							Name:  "subscribe",
-							Usage: "method is a subscription",
-						},
+						subscribeFlag,
 					},
 				},
 			},
@@ -207,8 +224,8 @@ func streamNetwork(ctx *cli.Context) error {
 	}
 	events := make(chan *simulations.Event)
 	sub, err := client.SubscribeNetwork(events, simulations.SubscribeOpts{
-		Current: ctx.Bool("current"),
-		Filter:  ctx.String("filter"),
+		Current: ctx.Bool(currentFlag.Name),
+		Filter:  ctx.String(filterFlag.Name),
 	})
 	if err != nil {
 		return err
@@ -279,16 +296,16 @@ func createNode(ctx *cli.Context) error {
 		return cli.ShowCommandHelp(ctx, ctx.Command.Name)
 	}
 	config := adapters.RandomNodeConfig()
-	config.Name = ctx.String("name")
-	if key := ctx.String("key"); key != "" {
+	config.Name = ctx.String(nameFlag.Name)
+	if key := ctx.String(keyFlag.Name); key != "" {
 		privKey, err := crypto.HexToECDSA(key)
 		if err != nil {
 			return err
 		}
 		config.ID = enode.PubkeyToIDV4(&privKey.PublicKey)
 		config.PrivateKey = privKey
 	}
-	if services := ctx.String("services"); services != "" {
+	if services := ctx.String(servicesFlag.Name); services != "" {
 		config.Lifecycles = strings.Split(services, ",")
 	}
 	node, err := client.CreateNode(config)
@@ -389,7 +406,7 @@ func rpcNode(ctx *cli.Context) error {
 	if err != nil {
 		return err
 	}
-	if ctx.Bool("subscribe") {
+	if ctx.Bool(subscribeFlag.Name) {
 		return rpcSubscribe(rpcClient, ctx.App.Writer, method, args[3:]...)
 	}
 	var result interface{}