go按行读取文件的三种实现方式汇总

// 全部读取后按换行拆分
func ReadFile1(path string) error {
	fileHanle,err := os.OpenFile(path, os.O_RDONLY, 0666)
	if err != nil {
		return err
	}
 
	defer fileHanle.Close()
 
	readBytes, err := ioutil.ReadAll(fileHanle)
	if err != nil {
		return err
	}
 
	results := strings.Split(string(readBytes), "\n")
 
	fmt.Printf("read result:%v", results)
	return nil
}

func ReadFile2(path string) error {
	fileHanle,err := os.OpenFile(path, os.O_RDONLY, 0666)
	if err != nil {
		return err
	}
 
	defer fileHanle.Close()
 
	reader := bufio.NewReader(fileHanle)
 
	var results []string
	// 按行处理txt
	for  {
		line, _, err := reader.ReadLine()
		if err == io.EOF {
			break
		}
		results = append(results, string(line))
	}
	fmt.Printf("read result:%v\n", results)
	return nil
}

func ReadFile3(path string)  error {
	fileHanle,err := os.OpenFile(path, os.O_RDONLY, 0666)
	if err != nil {
		return err
	}
 
	defer fileHanle.Close()
 
	scanner := bufio.NewScanner(fileHanle)
 
	var results []string
	// 按行处理txt
	for scanner.Scan(){
		lineTxt := strings.TrimSpace(scanner.Text())
 
		if len(lineTxt) == 0 {
			continue
		}
 
		results = append(results, lineTxt)
	}
	fmt.Printf("read result:%v\n", results)
	return nil
}

type SplitFunc func(data []byte, atEOF bool) (advance int, token []byte, err error)

func WordCounter(){
	const input = "Now is the winter of our discontent,\nMade glorious summer by this sun of York.\n"
	scanner := bufio.NewScanner(strings.NewReader(input))
	scanner.Split(bufio.ScanWords)
	count := 0
	for scanner.Scan() {
		count++
	}
	if err := scanner.Err(); err != nil {
		fmt.Fprintln(os.Stderr, "reading input:", err)
	}
	fmt.Printf("%d\n", count)
}

func ScanWords(data []byte, atEOF bool) (advance int, token []byte, err error) {
	// Skip leading spaces.
	start := 0
	for width := 0; start < len(data); start += width {
		var r rune
		r, width = utf8.DecodeRune(data[start:])
		if !isSpace(r) {
			break
		}
	}
	// Scan until space, marking end of word.
	for width, i := 0, start; i < len(data); i += width {
		var r rune
		r, width = utf8.DecodeRune(data[i:])
		if isSpace(r) {
			return i + width, data[start:i], nil
		}
	}
	// If we're at EOF, we have a final, non-empty, non-terminated word. Return it.
	if atEOF && len(data) > start {
		return len(data), data[start:], nil
	}
	// Request more data.
	return start, nil, nil
}