“纵有疾风来，人生不言弃”，这句话送给正在学习Golang的朋友们，也希望在阅读本文《在终端和文件中记录日志》后，能够真的帮助到大家。我也会在后续的文章中，陆续更新Golang相关的技术文章，有好的建议欢迎大家在评论留言，非常感谢！

我有这个函数可以将日志写入终端和日志文件：

// Run an executable and print its log in real-time and print its log into a file too.
func RunWithLog(pthExe string, arg []string, fLog *os.File, dir string) error {
    cmd := exec.Command(pthExe, arg...)
    if dir != "" {
        cmd.Dir = dir
    }

    stdout, err := cmd.StdoutPipe()
    if err != nil {
        return err
    }
    stderr, err := cmd.StderrPipe()
    if err != nil {
        return err
    }

    var wg sync.WaitGroup
    wg.Add(4)

    go streamRealTime(stdout, &wg)
    go streamRealTime(stderr, &wg)

    go streamToLogFile(stdout, fLog, &wg)
    go streamToLogFile(stderr, fLog, &wg)

    err = cmd.Start()
    if err != nil {
        return err
    }

    wg.Wait()

    err = cmd.Wait()
    return err
}

func streamRealTime(output io.ReadCloser, wg *sync.WaitGroup) {
    defer wg.Done()
    scanner := bufio.NewScanner(output)
    scanner.Split(bufio.ScanRunes)
    for scanner.Scan() {
        fmt.Print(scanner.Text())
    }
    err := scanner.Err()
    if err != nil {
        log.Printf("error: write log to terminal: %s", err.Error())
    }
}

func streamToLogFile(output io.ReadCloser, fLog *os.File, wg *sync.WaitGroup) {
    defer wg.Done()
    scanner := bufio.NewScanner(output)
    scanner.Split(bufio.ScanRunes)
    for scanner.Scan() {
        _, err := fLog.WriteString(scanner.Text())
        if err != nil {
            log.Printf("error: write log to file: %s", err.Error())
        }
    }
    err := scanner.Err()
    if err != nil {
        log.Printf("error: write log to file: %s", err.Error())
    }
}

上面的函数调用：

    // Log file.
    fLog, err := os.OpenFile(pathLog, os.O_APPEND, os.ModeAppend)
    if err != nil {
        return err
    }
    defer fLog.Close()

    err = RunWithLog(pathExe, []string{"-b"}, fLog, workDir)
    // ...

问题

问题是有些日志行打印到终端，有些行打印到文件，如下所示：

问题

如何确保所有日志行都打印到终端和文件？

正确答案

日志通过以下方式打印到终端和文件：

// Run an executable and print its log real-time and print its log into a file too.
func RunWithLog(pthExe string, arg []string, fLog *os.File, dir string) error {
    cmd := exec.Command(pthExe, arg...)
    if dir != "" {
        cmd.Dir = dir
    }

    stdout, err := cmd.StdoutPipe()
    if err != nil {
        return err
    }
    stderr, err := cmd.StderrPipe()
    if err != nil {
        return err
    }

    var wg sync.WaitGroup
    wg.Add(2)

    go streamLogs(stdout, fLog, &wg)
    go streamLogs(stderr, fLog, &wg)

    err = cmd.Start()
    if err != nil {
        return err
    }

    wg.Wait()

    err = cmd.Wait()
    return err
}

// Stream logs to both terminal and a file.
func streamLogs(output io.ReadCloser, fLog *os.File, wg *sync.WaitGroup) {
    defer wg.Done()
    scanner := bufio.NewScanner(output)
    scanner.Split(bufio.ScanRunes)
    for scanner.Scan() {
        // Stream to terminal:
        fmt.Print(scanner.Text())
        // Stream to a file:
        _, err := fLog.WriteString(scanner.Text())
        if err != nil {
            log.Printf("error: write log to file: %s", err.Error())
        }
    }
    err := scanner.Err()
    if err != nil {
        log.Printf("error: write log to terminal: %s", err.Error())
    }
}

测试

日志是相同的：

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