在CMD进程上调用的命令的读取错误输出挂起 [英] Reading error output hangs for command invoked on CMD process

问题描述

我有c＃控制台应用程序的ffmpeg命令调用。这是它

I have c# console app for ffmpeg command invocation. Here is it

class Program
{
    static void Main(string[] args)
    {
        ProcessStartInfo cmd = new ProcessStartInfo("cmd.exe");

        cmd.RedirectStandardInput = true;
        cmd.RedirectStandardOutput = true;
        cmd.RedirectStandardError = true;
        cmd.UseShellExecute = false;
        cmd.CreateNoWindow = true;
        cmd.WindowStyle = ProcessWindowStyle.Hidden;
        Process console = Process.Start(cmd);

        console.StandardInput.WriteLine(@"cd C:\Users\vishnu.aravind");                     
        console.StandardInput.WriteLine(@"ffmpeg -i sunp.avi -i Alarm03.wav  -c:v copy -c:a aac -strict experimental output.avi");     

        string errors = console.StandardError.ReadToEnd();

        Console.WriteLine("Video file is created.");
        Console.Read();
    }
}

如果我删除代码行

if I remove the line of code

string errors = console.StandardError.ReadToEnd();

此程序将正常工作。否则它挂起。

this program will work fine. Else it hangs. I need the error information if any, what to do, please help.

推荐答案

问题的原因

您的程序挂起，因为

Cause of a problem

Your program hangs because

• cmd 是一个交互式命令行应用程序，从而持续产生 std的输出。 out 和 std。错误流


• Process.StandardError.ReadToEnd（）读取 std的输出。错误流到达流结尾

• cmd is an interactive command line application and thus continually produces output for std. out and std. error stream
• Process.StandardError.ReadToEnd() reads the output of std. error stream of a process till it reaches end of stream

作为 cmd 命令行应用程序 - 它不会结束它的 std。错误流直到 cmd 终止 - 这就是为什么 Process.StandardError.ReadToEnd（） em> cmd 过程。

as cmd is an interactive command line application - it will not end it's std. error stream until process of cmd terminates - and that's why Process.StandardError.ReadToEnd() hangs when it is invoked on running cmd process.

执行有至少两个以下选项：

To get output for each command you execute there are at least two following options:

1. 使用单独的 Process 使用标准方法 StreamReader （ ReadToEnd（）和读取）方法）。



2. 使用单个进程 >应用程序 - 以交互方式读写它：

1. Start each command with separate Process instance - and read output with standard methods of StreamReader class (ReadToEnd() and Read() methods).

2. Use single Process instance for cmd application - to read and write to it interactively:

• 按照以下示例启动过程：

• Start process as in following example:

Process interactiveProcess = new Process();
string processOutput = "";

interactiveProcess.StartInfo.FileName = this.processPath;
interactiveProcess.StartInfo.Arguments = commandLineParameters;
interactiveProcess.StartInfo.UseShellExecute = false;
interactiveProcess.StartInfo.CreateNoWindow = false;
interactiveProcess.StartInfo.RedirectStandardInput = true;
interactiveProcess.StartInfo.RedirectStandardError = true;
interactiveProcess.Start();

interactiveProcess.EnableRaisingEvents = true;

interactiveProcess.ErrorDataReceived += new DataReceivedEventHandler((process, outputEventArgs) => processOutput += outputEventArgs.Data);

interactiveProcess.BeginErrorReadLine();

使用以下代码写命令

Write commands to cmd with following code

interactiveProcess.StandardInput.WriteLine(command);

要读取响应，您需要使用 System.Threading。 Thread.Sleep（）方法并等待 processOutput 变量在执行启动命令期间填充输出。

To read response you will need to use System.Threading.Thread.Sleep() method and wait till processOutput variable is populated with output during execution of started commands.

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