move: empty files finder to root

17-project-empty-file-finder/03-optimize/files/nonEmpty1.txt

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+learngoprogramming.com

17-project-empty-file-finder/03-optimize/files/nonEmpty2.txt

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+learngoprogramming.com

17-project-empty-file-finder/03-optimize/files/nonEmpty3.txt

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+learngoprogramming.com

17-project-empty-file-finder/03-optimize/main.go

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+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+)
+
+// You can easily write to a file using bash.
+//
+// However, when what you're creating is a library,
+// then you won't have that option. So, it's good to learn
+// how to write to a file using a byte slice.
+
+// ioutil.ReadDir
+// os.FileInfo
+
+func main() {
+	args := os.Args[1:]
+	if len(args) == 0 {
+		fmt.Println("Provide a directory")
+		return
+	}
+
+	files, err := ioutil.ReadDir(args[0])
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	// 1st: find the total size of all the empty files
+	var total int
+	for _, file := range files {
+		if file.Size() == 0 {
+			// +1 for the newline character
+			// when printing the filename
+			total += len(file.Name()) + 1
+		}
+	}
+
+	// 2nd: allocate a large enough byte slice in one go
+	names := make([]byte, 0, total)
+
+	for _, file := range files {
+		if file.Size() == 0 {
+			name := file.Name()
+
+			names = append(names, name...)
+			names = append(names, '\n')
+		}
+	}
+
+	err = ioutil.WriteFile("out.txt", names, 0644)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+
+	fmt.Printf("%s", names)
+}
+
+// See: https://www.tutorialspoint.com/unix/unix-file-permission.htm
+// See: http://permissions-calculator.org/