Geth中的main函数中调用了一个Run方法，该方法属于包cli中的类App的一个成员方法，下面是Run函数的具体实现
func (a *App) Run(arguments []string) (err error) {
a.Setup()
// handle the completion flag separately from the flagset since
// completion could be attempted after a flag, but before its value was put
// on the command line. this causes the flagset to interpret the completion
// flag name as the value of the flag before it which is undesirable
// note that we can only do this because the shell autocomplete function
// always appends the completion flag at the end of the command
shellComplete, arguments := checkShellCompleteFlag(a, arguments)
// parse flags
set, err := flagSet(a.Name, a.Flags)
if err != nil {
return err
}
set.SetOutput(ioutil.Discard)
err = set.Parse(arguments[1:])
nerr := normalizeFlags(a.Flags, set)
context := NewContext(a, set, nil)
if nerr != nil {
fmt.Fprintln(a.Writer, nerr)
ShowAppHelp(context)
return nerr
}
context.shellComplete = shellComplete
if checkCompletions(context) {
return nil
}
if err != nil {
if a.OnUsageError != nil {
err := a.OnUsageError(context, err, false)
HandleExitCoder(err)
return err
}
fmt.Fprintf(a.Writer, "%s %s\n\n", "Incorrect Usage.", err.Error())
ShowAppHelp(context)
return err
}
if !a.HideHelp && checkHelp(context) {
ShowAppHelp(context)
return nil
}
if !a.HideVersion && checkVersion(context) {
ShowVersion(context)
return nil
}
if a.After != nil {
defer func() {
if afterErr := a.After(context); afterErr != nil {
if err != nil {
err = NewMultiError(err, afterErr)
} else {
err = afterErr
}
}
}()
}
if a.Before != nil {
beforeErr := a.Before(context)
if beforeErr != nil {
fmt.Fprintf(a.Writer, "%v\n\n", beforeErr)
ShowAppHelp(context)
HandleExitCoder(beforeErr)
err = beforeErr
return err
}
}
args := context.Args()
if args.Present() {
name := args.First()
c := a.Command(name)
if c != nil {
return c.Run(context)
}
}
if a.Action == nil {
a.Action = helpCommand.Action
}
// Run default Action
err = HandleAction(a.Action, context)
HandleExitCoder(err)
return err
}
a.Setup仅仅是做了些简单的处理，比如相关的Auther、Email、重新创建Command切片等等.接下来我们看看下面的这个if判断
if args.Present() {
name := args.First()
c := a.Command(name)
if c != nil {
return c.Run(context)
}
}
由于我们前面在控制台输入的命令（启动命令 geth + 参数）长度不为0，因此执行
c.Run(context)
操作，此时的命令其实就是我们的console命令。接下来我们看看Run方法，Run方法的代码如下：
func (c Command) Run(ctx *Context) (err error) {
if len(c.Subcommands) > 0 {
return c.startApp(ctx)
}
if !c.HideHelp && (HelpFlag != BoolFlag{}) {
// append help to flags
c.Flags = append(
c.Flags,
HelpFlag,
)
}
set, err := flagSet(c.Name, c.Flags)
if err != nil {
return err
}
set.SetOutput(ioutil.Discard)
if c.SkipFlagParsing {
err = set.Parse(append([]string{"--"}, ctx.Args().Tail()...))
} else if !c.SkipArgReorder {
firstFlagIndex := -1
terminatorIndex := -1
for index, arg := range ctx.Args() {
if arg == "--" {
terminatorIndex = index
break
} else if arg == "-" {
// Do nothing. A dash alone is not really a flag.
continue
} else if strings.HasPrefix(arg, "-") && firstFlagIndex == -1 {
firstFlagIndex = index
}
}
if firstFlagIndex > -1 {
args := ctx.Args()
regularArgs := make([]string, len(args[1:firstFlagIndex]))
copy(regularArgs, args[1:firstFlagIndex])
var flagArgs []string
if terminatorIndex > -1 {
flagArgs = args[firstFlagIndex:terminatorIndex]
regularArgs = append(regularArgs, args[terminatorIndex:]...)
} else {
flagArgs = args[firstFlagIndex:]
}
err = set.Parse(append(flagArgs, regularArgs...))
} else {
err = set.Parse(ctx.Args().Tail())
}
} else {
err = set.Parse(ctx.Args().Tail())
}
nerr := normalizeFlags(c.Flags, set)
if nerr != nil {
fmt.Fprintln(ctx.App.Writer, nerr)
fmt.Fprintln(ctx.App.Writer)
ShowCommandHelp(ctx, c.Name)
return nerr
}
context := NewContext(ctx.App, set, ctx)
if checkCommandCompletions(context, c.Name) {
return nil
}
if err != nil {
if c.OnUsageError != nil {
err := c.OnUsageError(ctx, err, false)
HandleExitCoder(err)
return err
}
fmt.Fprintln(ctx.App.Writer, "Incorrect Usage:", err.Error())
fmt.Fprintln(ctx.App.Writer)
ShowCommandHelp(ctx, c.Name)
return err
}
if checkCommandHelp(context, c.Name) {
return nil
}
if c.After != nil {
defer func() {
afterErr := c.After(context)
if afterErr != nil {
HandleExitCoder(err)
if err != nil {
err = NewMultiError(err, afterErr)
} else {
err = afterErr
}
}
}()
}
if c.Before != nil {
err = c.Before(context)
if err != nil {
fmt.Fprintln(ctx.App.Writer, err)
fmt.Fprintln(ctx.App.Writer)
ShowCommandHelp(ctx, c.Name)
HandleExitCoder(err)
return err
}
}
if c.Action == nil {
c.Action = helpSubcommand.Action
}
context.Command = c
err = HandleAction(c.Action, context)
if err != nil {
HandleExitCoder(err)
}
return err
}
该主要是设置flag、解析输入的命令行参数、创建全局的context、将当前命令保存到全局context中,接下来调用HandleAction来处理命令，HandleAction的函数实现如下：
func HandleAction(action interface{}, context *Context) (err error) {
if a, ok := action.(ActionFunc); ok {
return a(context)
} else if a, ok := action.(func(*Context) error); ok {
return a(context)
} else if a, ok := action.(func(*Context)); ok { // deprecated function signature
a(context)
return nil
} else {
return errInvalidActionType
}
}
通过该函数代码重新经过相应的Init函数中的命令初始化方式进入相应的命令执行，当然，这只是简单的分析，实际的执行过程比这锅复杂得多。