Csharp/C#教程：如何使用C# 捕获进程输出分享

Intro

很多时候我们可能会需要执行一段命令获取一个输出，遇到的比较典型的就是之前我们需要用FFMpeg实现视频的编码压缩水印等一系列操作，当时使用的是FFMpegCore这个类库，这个类库的实现原理是启动另外一个进程，启动ffmpeg并传递相应的处理参数，并根据进程输出获取处理进度

为了方便使用，实现了两个帮助类来方便的获取进程的输出，分别是ProcessExecutor和CommandRunner，前者更为灵活，可以通过事件添加自己的额外事件订阅处理，后者为简化版，主要是只获取输出的场景，两者的实现原理大体是一样的，启动一个Process，并监听其输出事件获取输出

ProcessExecutor

使用示例，这个示例是获取保存nuget包的路径的一个示例：

usingvarexecutor=newProcessExecutor("dotnet","nugetlocalsglobal-packages-l"); varfolder=string.Empty; executor.OnOutputDataReceived+=(sender,str)=> { if(strisnull) return; Console.WriteLine(str); if(str.StartsWith("global-packages:")) { folder=str.Substring("global-packages:".Length).Trim(); } }; executor.Execute(); Console.WriteLine(folder);

ProcessExecutor实现代码如下：

publicclassProcessExecutor:IDisposable { publiceventEventHandler<int>OnExited; publiceventEventHandler<string>OnOutputDataReceived; publiceventEventHandler<string>OnErrorDataReceived; protectedreadonlyProcess_process; protectedbool_started; publicProcessExecutor(stringexePath):this(newProcessStartInfo(exePath)) { } publicProcessExecutor(stringexePath,stringarguments):this(newProcessStartInfo(exePath,arguments)) { } publicProcessExecutor(ProcessStartInfostartInfo) { _process=newProcess() { StartInfo=startInfo, EnableRaisingEvents=true, }; _process.StartInfo.UseShellExecute=false; _process.StartInfo.CreateNoWindow=true; _process.StartInfo.RedirectStandardOutput=true; _process.StartInfo.RedirectStandardInput=true; _process.StartInfo.RedirectStandardError=true; } protectedvirtualvoidInitializeEvents() { _process.OutputDataReceived+=(sender,args)=> { if(args.Data!=null) { OnOutputDataReceived?.Invoke(sender,args.Data); } }; _process.ErrorDataReceived+=(sender,args)=> { if(args.Data!=null) { OnErrorDataReceived?.Invoke(sender,args.Data); } }; _process.Exited+=(sender,args)=> { if(senderisProcessprocess) { OnExited?.Invoke(sender,process.ExitCode); } else { OnExited?.Invoke(sender,_process.ExitCode); } }; } protectedvirtualvoidStart() { if(_started) { return; } _started=true; _process.Start(); _process.BeginOutputReadLine(); _process.BeginErrorReadLine(); _process.WaitForExit(); } publicasyncvirtualTaskSendInput(stringinput) { try { await_process.StandardInput.WriteAsync(input!); } catch(Exceptione) { OnErrorDataReceived?.Invoke(_process,e.ToString()); } } publicvirtualintExecute() { InitializeEvents(); Start(); return_process.ExitCode; } publicvirtualasyncTask<int>ExecuteAsync() { InitializeEvents(); returnawaitTask.Run(()=> { Start(); return_process.ExitCode; }).ConfigureAwait(false); } publicvirtualvoidDispose() { _process.Dispose(); OnExited=null; OnOutputDataReceived=null; OnErrorDataReceived=null; } }

CommandExecutor

上面的这种方式比较灵活但有些繁琐，于是有了下面这个版本

使用示例：

[Fact] publicvoidHostNameTest() { if(!RuntimeInformation.IsOSPlatform(OSPlatform.Windows)) { return; } varresult=CommandRunner.ExecuteAndCapture("hostname"); varhostName=Dns.GetHostName(); Assert.Equal(hostName,result.StandardOut.TrimEnd()); Assert.Equal(0,result.ExitCode); }

实现源码：

publicstaticclassCommandRunner { publicstaticintExecute(stringcommandPath,stringarguments=null,stringworkingDirectory=null) { usingvarprocess=newProcess() { StartInfo=newProcessStartInfo(commandPath,arguments??string.Empty) { UseShellExecute=false, CreateNoWindow=true, WorkingDirectory=workingDirectory??Environment.CurrentDirectory } }; process.Start(); process.WaitForExit(); returnprocess.ExitCode; } publicstaticCommandResultExecuteAndCapture(stringcommandPath,stringarguments=null,stringworkingDirectory=null) { usingvarprocess=newProcess() { StartInfo=newProcessStartInfo(commandPath,arguments??string.Empty) { UseShellExecute=false, CreateNoWindow=true, RedirectStandardOutput=true, RedirectStandardError=true, WorkingDirectory=workingDirectory??Environment.CurrentDirectory } }; process.Start(); varstandardOut=process.StandardOutput.ReadToEnd(); varstandardError=process.StandardError.ReadToEnd(); process.WaitForExit(); returnnewCommandResult(process.ExitCode,standardOut,standardError); } } publicsealedclassCommandResult { publicCommandResult(intexitCode,stringstandardOut,stringstandardError) { ExitCode=exitCode; StandardOut=standardOut; StandardError=standardError; } publicstringStandardOut{get;} publicstringStandardError{get;} publicintExitCode{get;} }

More

如果只要执行命令获取是否执行成功则使用CommandRunner.Execute即可，只获取输出和是否成功可以用CommandRunner.ExecuteAndCapture方法，如果想要进一步的添加事件订阅则使用ProcessExecutor

Reference

https://github.com/rosenbjerg/FFMpegCore
https://github.com/WeihanLi/WeihanLi.Common/blob/dev/src/WeihanLi.Common/Helpers/ProcessExecutor.cs
https://github.com/WeihanLi/WeihanLi.Common/blob/dev/test/WeihanLi.Common.Test/HelpersTest/ProcessExecutorTest.cs
https://github.com/WeihanLi/WeihanLi.Common/blob/dev/test/WeihanLi.Common.Test/HelpersTest/CommandRunnerTest.cs

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