add Scan/Scanf functions for gcmd; improve gfile.IsEmpty

.example/frame/main/model/model1.go

@@ -10,6 +10,4 @@ func main() {
 	user, err := test.ModelUser().One()
 	g.Dump(err)
 	g.Dump(user)
-	user.Password = "1"
-	g.Dump(user.Update())
 }

.example/other/test.go

@@ -1,23 +1,11 @@
 package main
 
 import (
-	"os"
+	"fmt"
 
-	"github.com/olekukonko/tablewriter"
+	"github.com/gogf/gf/os/gcmd"
 )
 
 func main() {
-	data := [][]string{
-		[]string{"1/1/2014", "Domain name", "2233", "$10.98"},
-		[]string{"1/1/2014", "January Hosting", "2233", "$54.95"},
-		[]string{"1/4/2014", "February Hosting", "2233", "$51.00"},
-		[]string{"1/4/2014", "February Extra Bandwidth", "2233", "$30.00"},
-	}
-
-	table := tablewriter.NewWriter(os.Stdout)
-	table.SetBorder(false)
-	table.SetRowLine(false)
-	table.SetColumnSeparator("")
-	table.AppendBulk(data)
-	table.Render()
+	fmt.Println(gcmd.Scan("input:"))
 }

os/gcmd/gcmd_scan.go

@@ -0,0 +1,26 @@
+// Copyright 2019 gf Author(https://github.com/gogf/gf). All Rights Reserved.
+//
+// This Source Code Form is subject to the terms of the MIT License.
+// If a copy of the MIT was not distributed with this file,
+// You can obtain one at https://github.com/gogf/gf.
+//
+
+package gcmd
+
+import "fmt"
+
+// Scan prints <info> to stdout, reads and returns user input, which stops by '\n'.
+func Scan(info ...interface{}) string {
+	var s string
+	fmt.Print(info...)
+	fmt.Scan(&s)
+	return s
+}
+
+// Scanf prints <info> to stdout with <format>, reads and returns user input, which stops by '\n'.
+func Scanf(format string, info ...interface{}) string {
+	var s string
+	fmt.Printf(format, info...)
+	fmt.Scan(&s)
+	return s
+}

os/gfile/gfile.go

@@ -407,20 +407,22 @@ func Dir(path string) string {
 // IsEmpty checks whether the given <path> is empty.
 // If <path> is a folder, it checks if there's any file under it.
 // If <path> is a file, it checks if the file size is zero.
+//
+// Note that it returns true if <path> does not exist.
 func IsEmpty(path string) bool {
 	stat, err := Stat(path)
 	if err != nil {
-		return false
+		return true
 	}
 	if stat.IsDir() {
 		file, err := os.Open(path)
 		if err != nil {
-			return false
+			return true
 		}
 		defer file.Close()
 		names, err := file.Readdirnames(-1)
 		if err != nil {
-			return false
+			return true
 		}
 		return len(names) == 0
 	} else {