How to Stream Command Output in Go for Live Results?

Streaming Command Output for Live Results

Executing commands in Go allows you to interact with external processes, but if you need the output in real-time, there's a way to achieve it.

In your code snippet, the output is printed all at once after the command has completed. To display the output live, you can incorporate the technique outlined below:

// ... Previous code

for _, cp := range cmdParams {
    log.Printf("Starting %s in folder %s...", cp[1:], cp[0])
    cmd := exec.Command(cp[1], cp[2:]...)
    cmd.Dir = cp[0]

    stdout, err := cmd.StdoutPipe()
    if err != nil {
        log.Printf("%s cmd.StdoutPipe() error: %v\n", cp[1:], err)
        return
    }
    // Start command:
    if err = cmd.Start(); err != nil {
        log.Printf("%s start error: %v\n", cp[1:], err)
        return
    }

    // Stream command output:
    scanner := bufio.NewScanner(stdout)
    scanner.Split(bufio.ScanRunes)
    for scanner.Scan() {
        fmt.Print(scanner.Text())
    }
    if scanner.Err() != nil {
        log.Printf("Reading %s stdout error: %v\n", cp[1:], err)
        return
    }

    // Get execution success or failure:
    if err = cmd.Wait(); err != nil {
        log.Printf("Error running %s: %v\n", cp[1:], err)
        return
    }
    log.Printf("Finished %s", cp[1:])
}

// ... Remaining code

Explanation

This modification uses a bufio.Scanner to read the standard output of the command in real-time. The Split(bufio.ScanRunes) instructs the scanner to read individual characters, which allows you to display the output as it's being generated.

By repeatedly calling scanner.Scan() and printing the scanner.Text() until the end of the output is reached, you can stream the command's output live on the screen.

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