如何在.NET中生成进程并捕获其STDOUT？

Question

我需要生成一个作为控制台应用程序的子进程,并捕获其输出.

我为方法编写了以下代码:

string retMessage = String.Empty;
ProcessStartInfo startInfo = new ProcessStartInfo();
Process p = new Process();

startInfo.CreateNoWindow = true;
startInfo.RedirectStandardOutput = true;
startInfo.RedirectStandardInput = true;

startInfo.UseShellExecute = false;
startInfo.Arguments = command;
startInfo.FileName = exec;

p.StartInfo = startInfo;
p.Start();

p.OutputDataReceived += new DataReceivedEventHandler
(
    delegate(object sender, DataReceivedEventArgs e)
    {
        using (StreamReader output = p.StandardOutput)
        {
            retMessage = output.ReadToEnd();
        }
    }
);

p.WaitForExit();

return retMessage;

但是,这不会返回任何内容.我不相信该OutputDataReceived事件被回调,或者该WaitForExit()命令可能阻塞该线程,因此它永远不会回调.

有什么建议？

编辑:看起来我在回调中努力了.这样做:

return p.StandardOutput.ReadToEnd(); 

似乎工作正常.

Answer 1

这是我已经验证可以使用的代码.我用它来产生MSBuild并监听它的输出:

process.StartInfo.UseShellExecute = false;
process.StartInfo.RedirectStandardOutput = true;
process.OutputDataReceived += (sender, args) => Console.WriteLine("received output: {0}", args.Data);
process.Start();
process.BeginOutputReadLine();

Answer 2

我刚尝试了这件事,以下内容对我有用:

StringBuilder outputBuilder;
ProcessStartInfo processStartInfo;
Process process;

outputBuilder = new StringBuilder();

processStartInfo = new ProcessStartInfo();
processStartInfo.CreateNoWindow = true;
processStartInfo.RedirectStandardOutput = true;
processStartInfo.RedirectStandardInput = true;
processStartInfo.UseShellExecute = false;
processStartInfo.Arguments = "<insert command line arguments here>";
processStartInfo.FileName = "<insert tool path here>";

process = new Process();
process.StartInfo = processStartInfo;
// enable raising events because Process does not raise events by default
process.EnableRaisingEvents = true;
// attach the event handler for OutputDataReceived before starting the process
process.OutputDataReceived += new DataReceivedEventHandler
(
    delegate(object sender, DataReceivedEventArgs e)
    {
        // append the new data to the data already read-in
        outputBuilder.Append(e.Data);
    }
);
// start the process
// then begin asynchronously reading the output
// then wait for the process to exit
// then cancel asynchronously reading the output
process.Start();
process.BeginOutputReadLine();
process.WaitForExit();
process.CancelOutputRead();

// use the output
string output = outputBuilder.ToString();

Answer 3

我需要捕获stdout和stderr并且如果进程在预期时没有退出则超时.我想出了这个:

Process process = new Process();
StringBuilder outputStringBuilder = new StringBuilder();

try
{
process.StartInfo.FileName = exeFileName;
process.StartInfo.WorkingDirectory = args.ExeDirectory;
process.StartInfo.Arguments = args;
process.StartInfo.RedirectStandardError = true;
process.StartInfo.RedirectStandardOutput = true;
process.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
process.StartInfo.CreateNoWindow = true;
process.StartInfo.UseShellExecute = false;
process.EnableRaisingEvents = false;
process.OutputDataReceived += (sender, eventArgs) => outputStringBuilder.AppendLine(eventArgs.Data);
process.ErrorDataReceived += (sender, eventArgs) => outputStringBuilder.AppendLine(eventArgs.Data);
process.Start();
process.BeginOutputReadLine();
process.BeginErrorReadLine();
var processExited = process.WaitForExit(PROCESS_TIMEOUT);

if (processExited == false) // we timed out...
{
    process.Kill();
    throw new Exception("ERROR: Process took too long to finish");
}
else if (process.ExitCode != 0)
{
    var output = outputStringBuilder.ToString();
    var prefixMessage = "";

    throw new Exception("Process exited with non-zero exit code of: " + process.ExitCode + Environment.NewLine + 
    "Output from process: " + outputStringBuilder.ToString());
}
}
finally
{                
process.Close();
}

我正在将stdout和stderr连接到相同的字符串中,但如果需要,可以将它分开.它使用事件,所以它应该处理它们(我相信).我已成功运行,并将很快进行批量测试.

Answer 4

这里有一些完整而简单的代码.我使用它时工作正常.

var processStartInfo = new ProcessStartInfo
{
    FileName = @"C:\SomeProgram",
    Arguments = "Arguments",
    RedirectStandardOutput = true,
    UseShellExecute = false
};
var process = Process.Start(processStartInfo);
var output = process.StandardOutput.ReadToEnd();
process.WaitForExit();

请注意,这仅捕获标准输出 ; 它没有捕获标准错误.如果您想要两者,请对每个流使用此技术.

Answer 5

看起来你的两条线路无序.您在设置事件处理程序以捕获输出之前启动该过程.在添加事件处理程序之前,该过程可能刚刚完成.

像这样切换线.

p.OutputDataReceived += ...
p.Start();        

Answer 6

重定向流是异步的，并且在进程终止后可能会继续。Umar 提到要在进程终止后取消process.CancelOutputRead()。然而，这有可能丢失数据。

这对我来说工作可靠：

process.WaitForExit(...);
...
while (process.StandardOutput.EndOfStream == false)
{
    Thread.Sleep(100);
}

我没有尝试过这种方法，但我喜欢 Sly 的建议：

if (process.WaitForExit(timeout))
{
    process.WaitForExit();
}

Answer 7

设置 StartInfo 后，您需要调用 p.Start() 来实际运行该进程。事实上，您的函数可能挂在 WaitForExit() 调用上，因为该进程从未真正启动。