我有以下代码:

info = new System.Diagnostics.ProcessStartInfo("TheProgram.exe", String.Join(" ", args));
info.CreateNoWindow = true;
info.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
info.RedirectStandardOutput = true;
info.UseShellExecute = false;
System.Diagnostics.Process p = System.Diagnostics.Process.Start(info);
p.WaitForExit();
Console.WriteLine(p.StandardOutput.ReadToEnd()); //need the StandardOutput contents

我知道我正在启动的进程的输出大约有7MB长。在Windows控制台中运行它可以正常工作。不幸的是,从编程的角度来看,它会无限期地挂在WaitForExit上。还要注意,对于较小的输出(比如3KB),这段代码不会挂起。

ProcessStartInfo中的内部StandardOutput是否可能不能缓冲7MB?如果是,我该怎么办?如果不是,我做错了什么?


当前回答

我试图通过考虑Mark Byers, Rob, stevejay的回答,创建一个类来解决你使用异步流读取的问题。这样做,我意识到有一个与异步流程输出流读取相关的错误。

我在微软报告了这个漏洞:https://connect.microsoft.com/VisualStudio/feedback/details/3119134

简介:

You can't do that: process.BeginOutputReadLine(); process.Start(); You will receive System.InvalidOperationException : StandardOut has not been redirected or the process hasn't started yet. ============================================================================================================================ Then you have to start asynchronous output read after the process is started: process.Start(); process.BeginOutputReadLine(); Doing so, make a race condition because the output stream can receive data before you set it to asynchronous:

process.Start(); 
// Here the operating system could give the cpu to another thread.  
// For example, the newly created thread (Process) and it could start writing to the output
// immediately before next line would execute. 
// That create a race condition.
process.BeginOutputReadLine();

============================================================================================================================ Then some people could say that you just have to read the stream before you set it to asynchronous. But the same problem occurs. There will be a race condition between the synchronous read and set the stream into asynchronous mode. ============================================================================================================================ There is no way to acheive safe asynchronous read of an output stream of a process in the actual way "Process" and "ProcessStartInfo" has been designed.

对于您的情况,您最好使用其他用户建议的异步读取。但是您应该意识到,由于竞态条件,您可能会错过一些信息。

其他回答

上面的答案没有一个能起作用。

Rob解决方案挂起,“Mark Byers”解决方案获得已处理异常。(我尝试了其他答案的“解决方案”)。

所以我决定提出另一个解决方案:

public void GetProcessOutputWithTimeout(Process process, int timeoutSec, CancellationToken token, out string output, out int exitCode)
{
    string outputLocal = "";  int localExitCode = -1;
    var task = System.Threading.Tasks.Task.Factory.StartNew(() =>
    {
        outputLocal = process.StandardOutput.ReadToEnd();
        process.WaitForExit();
        localExitCode = process.ExitCode;
    }, token);

    if (task.Wait(timeoutSec, token))
    {
        output = outputLocal;
        exitCode = localExitCode;
    }
    else
    {
        exitCode = -1;
        output = "";
    }
}

using (var process = new Process())
{
    process.StartInfo = ...;
    process.Start();
    string outputUnicode; int exitCode;
    GetProcessOutputWithTimeout(process, PROCESS_TIMEOUT, out outputUnicode, out exitCode);
}

这段代码经过调试,工作完美。

我认为使用async,可以有一个更优雅的解决方案,即使同时使用standardOutput和standardError也不会出现死锁:

using (Process process = new Process())
{
    process.StartInfo.FileName = filename;
    process.StartInfo.Arguments = arguments;
    process.StartInfo.UseShellExecute = false;
    process.StartInfo.RedirectStandardOutput = true;
    process.StartInfo.RedirectStandardError = true;

    process.Start();

    var tStandardOutput = process.StandardOutput.ReadToEndAsync();
    var tStandardError = process.StandardError.ReadToEndAsync();

    if (process.WaitForExit(timeout))
    {
        string output = await tStandardOutput;
        string errors = await tStandardError;

        // Process completed. Check process.ExitCode here.
    }
    else
    {
        // Timed out.
    }
}

这是基于Mark Byers的回答。 如果你不在异步方法中,你可以使用string output = tStandardOutput.result;而不是等待

我们也有这个问题(或一个变体)。

试试下面的方法:

1)为p.WaitForExit(nnnn)添加超时;其中NNNN以毫秒为单位。

2)将ReadToEnd调用放在WaitForExit调用之前。这是我们看到MS推荐的。

罗布接了电话,帮我省了几个小时的时间。在等待之前读取输出/错误缓冲区:

// Read the output stream first and then wait.
string output = p.StandardOutput.ReadToEnd();
p.WaitForExit();

我知道这是晚餐,但是,在读完这一整页后,没有一个解决方案对我来说是有效的,尽管我没有尝试Muhammad Rehan,因为代码有点难理解,尽管我猜他是在正确的轨道上。当我说它不工作时,这并不完全正确,有时它会工作得很好,我猜这与EOF标记之前的输出长度有关。

不管怎样,对我来说有效的解决方案是使用不同的线程来读取StandardOutput和StandardError并写入消息。

        StreamWriter sw = null;
        var queue = new ConcurrentQueue<string>();

        var flushTask = new System.Timers.Timer(50);
        flushTask.Elapsed += (s, e) =>
        {
            while (!queue.IsEmpty)
            {
                string line = null;
                if (queue.TryDequeue(out line))
                    sw.WriteLine(line);
            }
            sw.FlushAsync();
        };
        flushTask.Start();

        using (var process = new Process())
        {
            try
            {
                process.StartInfo.FileName = @"...";
                process.StartInfo.Arguments = $"...";
                process.StartInfo.UseShellExecute = false;
                process.StartInfo.RedirectStandardOutput = true;
                process.StartInfo.RedirectStandardError = true;

                process.Start();

                var outputRead = Task.Run(() =>
                {
                    while (!process.StandardOutput.EndOfStream)
                    {
                        queue.Enqueue(process.StandardOutput.ReadLine());
                    }
                });

                var errorRead = Task.Run(() =>
                {
                    while (!process.StandardError.EndOfStream)
                    {
                        queue.Enqueue(process.StandardError.ReadLine());
                    }
                });

                var timeout = new TimeSpan(hours: 0, minutes: 10, seconds: 0);

                if (Task.WaitAll(new[] { outputRead, errorRead }, timeout) &&
                    process.WaitForExit((int)timeout.TotalMilliseconds))
                {
                    if (process.ExitCode != 0)
                    {
                        throw new Exception($"Failed run... blah blah");
                    }
                }
                else
                {
                    throw new Exception($"process timed out after waiting {timeout}");
                }
            }
            catch (Exception e)
            {
                throw new Exception($"Failed to succesfully run the process.....", e);
            }
        }
    }

希望这能帮助那些认为这很难的人!