如何在实时输出时将命令的stdout和stderr重定向到控制台和日志文件？ [英] How can I redirect the stdout and stderr of a command to both the console and a log file while outputting in real time?

问题描述

下面的代码完全符合我的要求，除了它只打印到控制台。

The following bit of code does exactly what I want, except it only prints to the console.

cmd := exec.Command("php", "randomcommand.php")

cmd.Stdout = os.Stdout
cmd.Stderr = os.Stderr

if err := cmd.Run(); err != nil {
    log.Fatal(err)
}

randomcommand .php：

randomcommand.php:

// randomcommand.php simply alternates output between stdout and stderr 20 times

$stdout = fopen('php://stdout', 'w+');
$stderr = fopen('php://stderr', 'w+');
for ($i = 1;$i <= 20; $i++) {
    fwrite($stdout, "stdout $i\n");
    fwrite($stderr, "stderr $i\n");
}

输出：

stdout 1
stderr 1
stdout 2
stderr 2
stdout 3
stderr 3
stdout 4
stderr 4
stdout 5
stderr 5
stdout 6
stderr 6
stdout 7
stderr 7
stdout 8
stderr 8
stdout 9
stderr 9
stdout 10
stderr 10
stdout 11
stderr 11
stdout 12
stderr 12
stdout 13
stderr 13
stdout 14
stderr 14
stdout 15
stderr 15
stdout 16
stderr 16
stdout 17
stderr 17
stdout 18
stderr 18
stdout 19
stderr 19
stdout 20
stderr 20

我想要实现的目标是：

1. 将命令的stdout和stderr实时打印到控制台;


2. 将命令的stdout和stderr记录到文件中，与控制台中显示的完全一致;


3. 尊重写入stdout和stderr的确切顺序，并且;


4. 不修改命令本身

1. Print the command's stdout and stderr to the console in real-time;
2. Log the command's stdout and stderr to a file, exactly as it appears in the console;
3. Respect the exact order of writes to stdout and stderr, and;
4. Not modify the command itself

我已尝试将命令stdout和stderr连接到扫描仪或使用io .Copy，每个都在goroutine中，但输出的顺序没有保持。可能因为goroutines之间的交替必须在输出交替的同时发生，这几乎是不可能的。

I've tried piping the command stdout and stderr into scanners or using io.Copy, each in a goroutine, but order of the output was not maintained. Probably because alternating between goroutines would have to occur at the same time as output alternates, which is just about impossible.

我也尝试使用选择，如这里。但是没有保持输出顺序。

I also tried the using "select" as in the examples from here. But order of output was not maintained.

与 Logstreamer相同的问题。

我必须尝试的另一个想法是看看我是否能以某种方式从控制台缓冲区中读取，但这感觉不对。

The other idea I have to try is to see if I can somehow just read from the console buffer, but this just doesn't feel right.

有没有人知道这是否可能并值得追求？

Does anyone know if this is even possible and worth pursuing?

推荐答案

<正如我在评论部分所说，这可以通过 MultiWriter 实现

package main

import (
    "io"
    "log"
    "os"
    "os/exec"
)

func main() {
    // Logging capability
    f, err := os.OpenFile("log.log", os.O_RDWR|os.O_CREATE|os.O_APPEND, 0666)
    if err != nil {
        log.Fatalf("Error opening file: %v", err)
    }
    defer f.Close()
    mwriter := io.MultiWriter(f, os.Stdout)
    cmd := exec.Command("ls")
    cmd.Stderr = mwriter
    cmd.Stdout = mwriter
    err = cmd.Run() //blocks until sub process is complete
    if err != nil {
        panic(err)
    }
}

当您声明命令时，在运行它之前，只需指定Stdout和Stderr正在使用上面定义的MultiWriter。此MultiWriter实例包含日志文件和标准输出。

When you declare your command, and before you run it, just specify that Stdout and Stderr are using the MultiWriter defined above. This MultiWriter instance contains both a log file and the standard output.

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