Implement #EZ5

app/main.go

@@ -54,6 +54,7 @@ const (
 	CommandTypeExternal
 	CommandTypeBuiltinExit
 	CommandTypeBuiltinEcho
+	CommandTypeBuiltinType
 )
 
 func getCommand(ctx *Context) (Command, error) {
@@ -71,24 +72,29 @@ func getCommand(ctx *Context) (Command, error) {
 }
 
 func tokenize(str string) []string {
-	tokens := make([]string, 2)
-	tokens = strings.Fields(str)
+	tokens := strings.Fields(str)
 	return tokens
 }
 
 func parseCommand(command_line string) (Command, error) {
 	tokens := tokenize(command_line)
+	if len(tokens) == 0 {
+		return makeCommandNone(), nil
+	}
 	if tokens[0] == "exit" {
 		return makeCommand(CommandTypeBuiltinExit, tokens), nil
 	}
 	if tokens[0] == "echo" {
 		return makeCommand(CommandTypeBuiltinEcho, tokens), nil
 	}
-	return makeCommandNone(), fmt.Errorf("%s: command not found", tokens[0])
+	if tokens[0] == "type" {
+		return makeCommand(CommandTypeBuiltinType, tokens), nil
+	}
+	return makeCommandNone(), fmt.Errorf("%s: not found", tokens[0])
 }
 
 func handleCommand(ctx Context, command Command) {
-	_ = ctx
+	// fmt.Printf("handleCommand():command=%#v\n", command)
 	switch command.command_type {
 	case CommandTypeNone:
 		return
@@ -96,6 +102,24 @@ func handleCommand(ctx Context, command Command) {
 		os.Exit(0)
 	case CommandTypeBuiltinEcho:
 		fmt.Fprintln(ctx.stdout, strings.Join(command.tokens[1:], " "))
+	case CommandTypeBuiltinType:
+		if len(command.tokens) != 2 {
+			fmt.Fprintln(ctx.stderr, "usage: type COMMAND")
+			return
+		}
+		parsed, err := parseCommand(command.tokens[1])
+		if err != nil {
+			fmt.Fprintln(ctx.stderr, err)
+			return
+		}
+		switch parsed.command_type {
+		case CommandTypeNone:
+			panic("impossible parseCommand() result")
+		case CommandTypeExternal:
+			fmt.Fprintf(ctx.stdout, "%s is an external command\n", parsed.tokens[0])
+		default:
+			fmt.Fprintf(ctx.stdout, "%s is a shell builtin\n", parsed.tokens[0])
+		}
 	}
 }